CHAPTER 12 243 Biology Term 2 STPM Chapter 12 Immunity 3. Common initial and chronic symptoms include fever, malaise, joint pains, fatigue, and temporary loss of cognitive abilities. Because they are so often seen with other diseases, these signs and symptoms are not part of the diagnostic criteria for SLE. 4. SLE causes an increased rate of foetal death in utero and spontaneous abortion (miscarriage). The overall live-birth rate in SLE patients has been estimated to be 72%. Pregnancy outcome appears to be worse in SLE patients whose disease flares up during pregnancy. Infant with SLE may be born from a mother with SLE, most commonly presenting with a rash and sometimes with systemic abnormalities such as heart block. Causes of SLE 1. There is no one specific cause of SLE. There are, however, a number of environmental triggers and a number of genetic susceptibilities. 2. The first mechanism may arise genetically. Research indicates SLE may have a genetic link. SLE does run in families, but no single causal gene has been identified. Instead, multiple genes appear to influence a person’s chance of developing lupus when triggered by environmental factors. The most important genes are located in the HLA region on chromosome 6, where mutations may occur randomly (de novo) or may be inherited. HLA class I, class II, and class III are associated with SLE, but only classes I and II contribute independently to increased risk of SLE. Some of the susceptibility genes may be population specific. 3. The second mechanism may be due to environmental factors. These factors may not only exacerbate existing SLE conditions, but also trigger the initial onset. Researchers have sought to find a connection between certain infectious agents (viruses and bacteria), but no pathogen can be consistently linked to the disease. 4. Some researchers have found that women with silicone gel-filled breast implants have produced antibodies to their own collagen, but it is not known how often these antibodies occur in the general population, and there are no data that show these antibodies cause connective tissue diseases such as SLE. 5. Drug-induced lupus erythematosus is a reversible condition that usually occurs in people being treated for a long-term illness. Druginduced lupus mimics SLE. However, symptoms of drug-induced lupus generally disappear once the medication that triggered the episode is stopped. More than 38 medications can cause this condition, the most common of which are procainamide, isoniazid, hydralazine, quinidine, and phenytoin.
CHAPTER 12 244 Biology Term 2 STPM Chapter 12 Immunity Treatment of SLE 1. The treatment of SLE involves preventing flares and reducing their severity and duration when they occur. Treatment can include corticosteroids and anti-malarial drugs. Certain types of lupus nephritis such as diffuse proliferative glomerulonephritis require bouts of cytotoxic drugs. These drugs include cyclophosphamide and mycophenolate. 2. Due to the variety of symptoms and organ system involvement with SLE, its severity in an individual must be assessed in order to successfully treat SLE. Mild or remittent disease may, sometimes, be safely left untreated. If required, non-steroidal anti-inflammatory drugs and antimalarials may be used. 3. Disease-modifying anti-rheumatic drugs (DMARDs) are used preventively to reduce the incidence of flares, the process of the disease, and lower the need for steroid use; when flares occur, they are treated with corticosteroids. DMARDs commonly in use are antimalarials such as plaquenil and immuno-suppressants (e.g. methotrexate and azathioprine). 4. In more severe cases, medications that modulate the immune system (primarily corticosteroids and immunosuppressants) are used to control the disease and prevent recurrence of symptoms (known as flares). 5. Since a large percentage of people with SLE suffer from varying amounts of chronic pain, stronger prescription analgesics (pain killers) may be used if over-the-counter drugs (mainly non-steroidal anti-inflammatory drugs) do not provide effective relief. 6. Intravenous immunoglobulins (IVIGs) may be used to control SLE with organ involvement, or vasculitis. It is believed that they reduce antibody production or promote the clearance of immune complexes from the body, even though their mechanism of action is not wellunderstood. Unlike immunosuppressives and corticosteroids, IVIGs do not suppress the immune system, so there is less risk of serious infections with these drugs. 7. Avoiding sunlight is the primary change to the lifestyle of SLE sufferers, as sunlight is known to exacerbate the disease, as is the debilitating effect of intense fatigue. These two problems can lead to patients becoming housebound for long periods of time. 8. Renal transplants are the treatment of choice for end-stage renal disease, which is one of the complications of lupus nephritis, but the recurrence of the full disease is common in up to 30% of patients.
CHAPTER 12 245 Biology Term 2 STPM Chapter 12 Immunity Objective Questions 1. The main function of lymphatic system is to A enable transfer of substances between blood and body cells B transport lymph from interstitial fluid into blood circulation C produce antibodies for fighting against bacteria and viruses D filter bacteria before they are engulfed by phagocytes in lymph nodes 2. The table below shows antibody classes and their functions. Antibody Function I Ig M w Secreted from bloodstream into tears and mucus to bind to microbes II Ig A x Effective in agglutinating antigens and in reactions involving complement III Ig G y Triggers the release of histamine that causes an allergic reaction IV Ig E z Moves across the placenta and confers passive immunity on the foetus Which combination is correct? I II III IV A x w z y B x z w y C y w z x D y z x w 3. Which about the component of the immune system is correct? A Thymus is a place where B lymphocytes develop and mature B Epitope is a small portion of an antibody that binds to an antigen C Antigen is any substance that causes a response from B or T cells D Antibody is a protein, which is secreted by T lymphocyte to bind to a particular antigen 4. Which statement is true of T cells? I T cells produce interleukin-1 II T cells produce complement immunoglobulins III Cytotoxic T cells kill body cells infected with virus IV Suppressor T cells inhibit the activities of T cytotoxic cells A I and II B I and IV C II and III D III and IV 5. Which of the following occurs only in the cell-mediated immune response? A Lysis of infected cells B Cloning of memory cells C Antigen presented by the macrophage D Activation of helper cells by antigen presenting cells 6. The diagram represents a flow chart of the humoral response. Z Antigen stimulates X Y Plasma cell Which combination is correct? XY Z A B cell Antibody Memory B cell B B cell Memory B cell Antibody C T cell Memory T cell Cytotoxic T cell D T cell Memory T cell Helper T cell STPM PRACTICE 12
CHAPTER 12 246 Biology Term 2 STPM Chapter 12 Immunity I II III IV A P Q R S B R P S Q C R S Q P D S P R Q 10. Why the donor’s and the recipient’s major histocompatibility complex must be matched before any organ transplant? A There are less antigens on the donated organs recognised by the recipient’s body as non-self B No immune response is triggered in the recipient’s body after the transplant C There is an increased risk of organ rejection and infections in the recipient’s body after the transplant D The recipient needs to use more immunosuppressants 11. Which response is true of the human immune system? A Responds to antigen with the production of lymphocyte clone cells B Responds very slowly to secondary attack C Responds so that T cells produce antibodies D Produces different antibodies against same antigen 12. Which statements are true of B cells? I They form immunity through cellmediated response II They form immunity through humoral response III They are produced and matured in the bone marrow IV They are produced in the bone marrow and become matured in the thymus gland A I and II B I and III C II and III D III and IV 7. Which type of cell corresponds correctly to its function in the immune response? Type of cell Function I B cell II Helper T cell III Cytotoxic T cell X Destroys cancer cell Y Differentiates into memory and plasma cells Z Secretes cytokines that activate B cells I II III A X Y Z B X Z Y C Y X Z D Y Z X 8. What is the first event that stimulates a primary immune response in our bodies if we are infected by virus? A A viral protein complex is presented to MHC B The virus is recognised as non-self C Perforin is produced by cytotoxic T cells D The virus is phagocytosised by APC 9 . The cells of the immune system and their functions are shown in the table below. Type of immune response Function I B cell II Helper T cell III Macrophage IV Mast cell P Secretes interleukin-2 Q Triggers allergy symptoms R Carries out humoral immunity S Kills microorganisms by phagocytosis Which type of immune response corresponds correctly to its function?
CHAPTER 12 247 Biology Term 2 STPM Chapter 12 Immunity 13. What is injected into the body for treatment of dog bite? A Weakened viruses B Serum containing antigens C Serum containing specific antibodies D Dead bacteria 14. The immune response of a human body after a second pathogen infection is shown in the graph below. Antibody concentration (arbitrary units) Time (days) Primary immune response Secondary immune response 7 14 21 28 35 42 49 56 101 102 103 104 0 What causes a rapid and higher response upon the second exposure? I The presence of memory B cell after the first infection II The presence of memory T cell after the first infection III The presence of helper T cell after the first infection IV The presence of killer T cell after the first infection A I and II B I and III C II and IV D III and IV 15. A schematic diagram of the human immune response is shown in the diagram below. Precursor cell from the bone Cell P Cell Q Moves to lymph node Substance Y Substance Z Cell R Which is true of the above diagram? A Cell P secretes lymphokine and then divides to form cell Q and cell R in the presence of substance Y. B Cell Q makes other lymphocytes willing to produce antibodies. C Cell R responds quickly to a repeated infection of certain illnesses. D Substances Z regulates lymphocytes which is involved in immune response. 16. Foreign transplanted organ will be rejected because the A donor cells have the same class I MHC proteins as the recipient cells B recipient immunoglobulin E will stimulate allergic response C recipient helper T cells produce interleukin-2 to stimulate the secretion of antibodies D recipient cytotoxic T cell produces perforin to destroy the donated cells
CHAPTER 12 248 Biology Term 2 STPM Chapter 12 Immunity Structured Questions 1. The diagram shows the interaction between antibodies and antigens. (a) Name the structure P, and state its function. [2] (b) Name the cell that produces Q. [1] (c) State two functions of the antigen-antibody complex. [2] (d) (i) What type of immune response is represented by the above diagram? [1] (ii) What are the roles of helper T cell in immune response mentioned in (d)(i)? [2] 2. The diagram below shows an antibody molecule, IgM. (a) What is the definition of antibody. [2] (b) Where is antigen would bind? Circle your answer on the diagram above. [1] (c) (i) State how IgM reacts to antigen. [1] (ii) Why IgM does not identify foetus in pregnant women as a foreign body? [2] (iii) Which type of antigen can be recognised by IgM? (d) Name the class of antibody that is involved in passive immunity in foetus. [1] Essay Questions 1. (a) List the organs and structures of the lymphatic system and describe their functions. [8] (b) Explain why transplanted organ may be rejected by the body. [3] (c) State the steps taken to prevent organ rejection after transplant. [4] 2. (a) Explain how our body acquires active immunity through humoral response. [10] (b) State one function for each of the following cells. [5] (i) Macrophage (iv) Suppressive T cell (ii) Helper T cell (v) Plasma cell (iii) Cytotoxic T cell 3. What is AIDS? Explain the mechanism of infection, symptoms and preventions of AIDS. [15] Q P
CHAPTER 12 249 Biology Term 2 STPM Chapter 12 Immunity Quick Check 1 1. Each class of immunoglobulins has specific functions to defend the body. IgM starts the cascade effect of complement proteins and can agglutinate antigen. IgG activates the production of complement proteins and neutralise various toxins and provides passive natural immunity to baby from the mother. IgA found in surface with mucus such as in the respiratory tract, digestive and reproductive canals destroys various pathogens. IgE attacks parasitic worms or surface pathogens. IgD is found on the B cell surfaces and serves as a receptor for antigen. 2. Phagocytes are white blood cells that can phagocytosise microbes. They include macrophages derived from monocytes, neutrophils, and eosinophils, and basophils. They are important for non-specific immune response, including macrophages, neutrophils, eosinophils and basophils, by eating up antigens. Quick Check 2 1. MHC is a group of genes controlling glycoproteins found on the surface of plasma membrane of body cells. There are at least two genes involved, each with more than a hundred types of alleles. There are thousands of combinations of these proteins on the cell surface that determine the ‘self ’ markers. These proteins act as antigens if tissues are donated to another individual. 2. The recipient will have the organ for life and there are surface antigens on it all the time. Without the drug, the antigens are attacked by the immune system as non-self. With the drug, there will not be a massive attack on the antigens and lesser chance of rejection. Quick Check 3 1. HIV releases RNA into helper T lymphocyte together with an enzyme called reverse transcriptase. The RNA is converted into DNA and the DNA is incorporated into a host chromosome and becomes part of it. When host cell divide, the daughter cells contain the viral DNA too. This happens for at least 6 years and without reason, transcription of the viral DNA produces thousands of copies of RNA and also viral protein units. These units assemble to form HIV particles and bud out of the host cell, carrying away the host membrane as their own membrane. 2. A HIV-positive individual has the viral genes in helper T lymphocytes, which resulted in loss of immunity. Many opportunistic diseases will attack that person and he will eventually dies from such diseases. STPM Practice 12 Objective Questions 1. B 2. A 3. C 4. D 5. A 6. B 7. D 8. A 9. B 10. B 11. A 12. C 13. C 14. A 15. C 16. D Structured Questions 1. (a) P: epitope Function: acts as antigenic determinant for binding with antibody’s binding site (b) Plasma cell (c) t 5POFVUSBMJTFUIFBOUJHFOTTPUIBUUIFZCFDPNF non-toxic. t 5P QSFDJQJUBUF UIF BOUJHFOT TP UIBU UIFZ DBO be easily engulfed by phagocytes including macrophages. (d) (i) Humoral response (ii) t 5P CJOE XJUI QSFTFOUFE FQJUPQF BOE release interleukin-2 t Interleukin-2 released causes the lymphocyte B to divide and becomes plasma cells. 2. (a) Antibody is a specific protein produced by matured lymphocyte B cells after stimulated by a type of antigen. The antibody can inactivate the specific antigen by agglutination or binding to it. (b) (c) (i) Agglutinates it (ii) This is due to IgM too large to cross the placenta to reach the foetus. Since the foetus is protected by membrane the foetal antigen cannot be detected or presented by the immune system (iii) Antigen that is phagocytosised or presented by APC in the body fluid (d) IgA ANSWERS
CHAPTER 12 250 Biology Term 2 STPM Chapter 12 Immunity Essay Questions 1. B t ćFPSHBOTBOETUSVDUVSFTPGMZNQIBUJDTZTUFN are lymphatic vessels, lymph nodes, mucosa associated lymphatic tissues, spleen and thymus gland. t -ZNQIBUJD DBQJMMBSJFT BMMPX UJTTVF ĘVJE UP enter as lymph, to drain it back into the blood. t ćF WFTTFMT QBTT UISPVHI MZNQI OPEFT BMPOH certain strategic positions, such as the groin region. t ćFMZNQIOPEFTBMMPXMZNQIPDZUFTUPUBLFVQ position to meet antigents and divide to form clones. t ćFMZNQIOPEFT SFNPWFNJDSPCFTPSQJFDFT of broken body cells by phagocytosis. t ćF BEFOPJE BOE UPOTJM MZNQIBUJD UJTTVFT remove microbes and antigens that are trapped from air or entered together with food. t ćF TQMFFO QSPWJEFT TJUFTGPS MZNQIPDZUFT UP bind and remove antigens, white blood cells and platelets. t ćZNVTHMBOEBDUMJLFBHJBOUMZNQIOPEFXJUI lymphatic capillaries. t ćFDFMMTDBOQSPEVDFUIFDIFNJDBMSFRVJSFEUP stimulate receptors for B lymphocytes. t ćFTZTUFNBDUTBTBTJFWFUPSFNPWFBOUJHFOT that enters it from the tissues or specific part such as the tonsil. t *UQSPWJEFT TJUFTGPS5MZNQIPDZUFT UPBUUBDI divide and mature. (b) t -ZNQIPDZUFT DBO SFDPHOJTF TFMGNBSLFST BOE does not attack own proteins. This is because during embryonic development, stem cells that meet own proteins and reacted will not be developed into lymphocytes. t )PXFWFS XIFOGPSFJHOPSHBOJTUSBOTQMBOUFE proteins of the cell surface or imported free proteins act as antigens. Lymphocytes recognise them as non-self when antigenpresenting cell (APC) presented them. t $ZUPUPYJD 5 MZNQIPDZUFT XJUI UIF IFMQ PG helper T cells produce perforins and lysis of surface cells of transplant organ occurs. Cells within the organ are attacked too. t # MZNQIPDZUFT QSPEVDFT JNNVOPHMPCVMJOT or antibodies that bind to the surfaces of the cells or proteins within the blood vessels. This is followed by inflammation response and destruction of cells by phagocytes. t ćFDFMMTPSUJTTVFTTMPXMZEJFBOEUIFZDBOOPU perform their functions. They are rejected. (c) t 5JTTVFNBUDIJOH ćF UJTTVFT PG EPOPS BOE recipient are typed to see whether they are matching. Tissues of donor that are identical to the recipient will not result in any rejection. t "ęFSUSBOTQMBOU UIFCPOFNBSSPXJTJSSBEJBUFE with X-ray to slow down the production of white blood cells. This will slow down the rejection, as the number of phagocytes is smaller. t *NNVOPTVQQSFTTJPOESVHTVDIBTDZDMPTQPSJO is administered to slow down the immune response. t .PSF BEWBODFE PS TQFDJĕD ESVH NJHIU CF taken to act only on certain markers. This cuts down the risk of secondary attack by other opportunistic pathogens as the body is weakened. t *OUIFOFBSGVUVSF PSHBOTPGUSBOTHFOJDBOJNBMT that have human markers can be engineered or cultured for human transplant. This would produce a perfect match. 2. B t 8IFO BOUJHFO FOUFST UIF CPEZ GPS UIF ĕSTU time, macrophage or virgin B cell engulfs it. t ćFO UIF BOUJHFO JT DVU JOUP FQJUPQFT BOE presented on the macrophage or the B cell surface. t )FMQFS 5 DFMM XJUI DPNQMFNFOUBSZ SFDFQUPST recognises the epitopes and binds to it. t .BDSPQIBHF TUJNVMBUFT UIF IFMQFS 5 DFMM UP produce interleukin-1, which causes helper T cell to produce interleukin-2. t *OUFSMFVLJO DBVTFT UIF EFUBDIFE # DFMM UP divide by mitosis. t "DMPOFPGUIJTTQFDJĕD#DFMMTJTGPSNFEffiUIFTF are the plasma cells. t 4PNF PG UIF DMPOF DFMMT CFDPNFT NFNPSZ # cells. t ćFQMBTNBDFMMTQSPEVDFBOUJCPEJFTXIJDIBSF complementary to the antigens. t ćFTFBOUJCPEZNPMFDVMFTCJOEUPUIFBOUJHFOT and remove them. t "ęFS UIF BOUJHFOT BSF SFNPWFE UIF QMBTNB cells disappears. t ćJT MFBWFT CFIJOE TPNF UIF BOUJCPEJFT BOE memory cells. t ćVT UIF CPEZ IBT BDRVJSFE BO BDUJWF immunity and prepared for the attack of the same antigen for a second time. (b) (i) Macrophage engulfs antigens and acts as antigen presenting cell. (ii) Helper T cell binds to specific presented antigen and produces interleukin-2 to cause T or B cells to divide. (iii) Cytotoxic T cell can produce perforin and punch holes in the infected body cell, thus removing the viruses within. (iv) Suppressive T cell suppresses the activities of the effector T or the plasma cells after the antigen disappeared.
CHAPTER 12 251 Biology Term 2 STPM Chapter 12 Immunity (v) Plasma cell produces specific antibody molecules to remove complementary antigen. 3. t "*%4JTBEJTFBTFXJUINBOZTZNQUPNTDBVTFECZ attack of HIV on helper T (CD4) lymphocytes and macrophages, resulting in loss of immunity. t 8IFO UIF QBUJFOU MPTFT IJT JNNVOJUZ NBOZ opportunistic diseases will attack him and finally he dies from such diseases. t *O UIF ĕSTU ZFBST B QFSTPO JOGFDUFE XJUI )*7 shows no sign of the sickness except that he has HIV particles and antibodies in his blood and the viral genes in the lymphocytes and macrophages. The mechanism of infection are as follows: t 4FYVBMJOUFSDPVSTF*OGFDUFETFNJOBMĘVJEFKBDVMBUFE into the vagina, mouth or rectum can transmit HIV to the partner. t *OGFDUFE CMPPE FBTJMZ QBTTFT )*7 QBSUJDMFT PS infected lymphocytes to another person. This can be done through sharing of contaminated needle among drug addicts. Contaminated blood received by haemophiliac or recipient or mutual wound contact can transmit HIV. t .PUIFS UPGPFUVTćJTJT UISPVHI UIFQMBDFOUB BU around 25-50% chances and also through mother’s milk. The symptoms are as follows: t ćFĕSTUTJHOPGJOGFDUJPOJT UIFTBNFBTBOBUUBDL of cold and after a few days the person recovered. Nothing happens until more than 6 years. t ćFO UIFSFJTWFSZSBQJEMPTTPGXFJHIU t 'FWFSBOETXFBUJOHBUOJHIUPDDVS t ćFMZNQIOPEFTCFDPNFFOMBSHFE t %JBSSIPFB UJSFEOFTTBOEEFNFOUJBPDDVS t 0QQPSUVOJTUJDEJTFBTFTMJLFDPVHI ZFBTUJOGFDUJPO in the mouth and sexual organs, pneumonia, Kaposi sarcoma infect the patient. Preventions of AIDS can be done as follows: t 1SPUFDUJPOJTVTFEEVSJOHTFYVBMJOUFSDPVSTF t *UJTBEWJTBCMFUPMJNJUUPPOFTFYVBMQBSUOFS t 4IBSJOHPGTZSJOHFGPSJOKFDUJPOTIPVMECFBWPJEFE t "MMCMPPETSFDFJWFEBSFUFTUFE)*7GSFFCFGPSFVTF t ćF QVCMJD TIPVME CF FEVDBUFE PO UIF NPEF PG transmission.
CHAPTER INFECTIOUS DISEASES Concept Map 13 Infectious diseases Dengue Cholera Tuberculosis Malaria Types of infectious agents virus, bacteria, fungi, protoctist, nematods, helminths and arahnids Causative agents Dengue fever virus (DENV) Causative agents Bacteria (Vibrio cholerae) Causative agents Bacteria (Mycobacterium tuberculosis) Causative agents Protoctist (Plasmodium) Symptoms: 1. Fever 2. Headache 3. Muscle and joint pains 4. Skin rash Symptoms: 1. Gastrointestinal tract upset 2. Diarrhoea 3. Vomitting Symptoms: 1. Prolonged cough 2. Chest pain 3. Fever 4. Weight loss Symptoms: 1. Fever 2. Anaemia 3. Chills 4. Flu like illness Transmission Aedes mosquito transfers blood from an infected person to an uninfected person Transmission Water-borne and housefly Transmission Aerosol from patient inhaled by uninfected Transmission Anopheles mosquito transfers blood from an infected person to an uninfected person Prevention Eliminate Aedes mosquito and its habitat Prevention Chlorinate water supply and safe disposal of sewage Prevention Vaccination, improve housing and health, early treatment Prevention Eliminate Anopheles mosquito and Plasmodium parasites Bilingual Keywords Infectious diesases – Penyakit berjangkit Prevention – Pencegahan Infectious agents – Agen berjangkit Transmission – Penjangkitan Causative agent – Agen penyebab Vector – Vektor Symptoms – Tanda penyakit Vaccination – Pemvaksinan
Learning Outcomes CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases Students should be able to: (a) explain what is meant by an infection and an infectious disease; (b) outline the types of infectious agents. 13.1 Infectious Disease 13.1 Infectious Disease 1. A disease is any condition that impairs the normal functioning of the body. 2. There are many causes of disease. (a) Genetic diseases, caused by genes such as Down’s syndrome. (b) Infectious diseases, caused by some microorganisms called pathogens. These microorganisms include bacteria, fungi and viruses. (c) Non-infectious diseases, caused by natural aging, a lack of a particular nutrient in a diet or poor life style. These include anaemia, arthritis and diabetes. 3. Before a pathogen such as bacteria, virus and parasite can cause an infectious disease, infection must occur. Infection 1. Infection is the invasion and multiplication within the cells or in tissue fluid of microorganisms such as bacteria, viruses, and parasites that are not normally present within the body. Microorganisms that live naturally in the body are not considered infections. For example, bacteria that normally live within the mouth and intestine are not infections. 2. Infection is an abnormal condition caused by pathogens affecting the organisms e.g. human, which reduces the effectiveness of the functions our body. It may produce ill-health, absence of well-being or abnormal condition and a reduced effectiveness of functions especially our immune system. It may result in poor physical, mental or social well-being. 3. Infection usually produces illness with a set of symptoms and be clinically apparent. The symptoms are directly caused by damage to tissues, indirectly through the toxins produced by the pathogens or the reactions of host tissues to these organisms. The symptoms of an infection depend on the type of disease. Some signs of infection affect the whole body generally, such as fatigue, loss of appetite, weight loss, fevers, night sweats, chills, aches and pains. Others are specific to individual body parts, such as skin rashes, coughing, or a runny nose. 4. An infection may cause no symptoms called latent infection e.g. before the on set full bloom AIDS on an HIV positive person and be sub-clinical e.g. at the beginning of TB infection when no clinical test can confirm the presence of TB bacteria. An infection that is inactive or dormant is called a latent infection. 5. An infection may remain localised, or it may spread through the blood or lymphatic vessels to become systemic (body wide). Example, For many pathogens, symptoms of the disease do not appear immediately on PUMLJ[PVU-VY[OLÄYZ[ML^[OYLL days after infection (the time ^OLU`V\ÄYZ[IYLH[OLK[OL viruses in), nothing very much happens. This is called the incubation period. Info Bio STPM 2014/P2/Q20(a) INFO Infectious Disease
CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases gonorrhoea, a sexually transmitted disease may just affect the sexual reproductive organs but if untreated it can affect the joints of our bones and our heart! 6. Hosts can fight infections using their defense system. Mammalian hosts react to infections with an innate response, often involving inflammation and non-specific response, followed by an adaptive response involving specific immune response. Pharmaceuticals such as antibiotics can also help fight infections. 7. A short-term infection is an acute infection e.g. throat infection. A long-term infection is a chronic infection e.g. chronic bronchitis caused by TB. 8. Infection can be primary and secondary infections. The primary infection usually involves a small initial dose of virus and leads to little impact for the host. A secondary infection is an infection that occurs during or after treatment of another, already existing infection. It may result from the treatment itself or from alterations in the immune system. For example, the primary infection of AIDS is the HIV infecting the helper T lymphocytes resulting in the loss of immune response. The secondary infection may be caused by an opportunistic cold virus that destroyed the lungs and causes death. 9. The two most common infections are viral and bacterial. A comparison of their typical symptoms is shown in Table 13.1. Table 13.1 Comparison of viral and bacterial infection Characteristic Viral infection Bacterial infection Typical symptoms 1. Systemic, involve many different parts of the body or more than one body system at the same time; i.e. a runny nose, sinus congestion, cough, body aches etc. 2. Can be local at times as in viral conjunctivitis or “pink eye” and herpes. 3. Few are painful, like herpes. The pain is often itchy or burning. 1. Localised redness, heat, swelling and pain; e.g. only one ear may be infected by bacteria. Local pus and milky-coloured liquid are produced. 2. Rarely systemic except in syphilis in which skin and brain are infected. 3. Usually painful e.g. sore throat. The pain is often sharp or unbearable. Infectious Disease 1. Infectious disease is a disease caused by other living organisms which invade the body and live parasitically. Such organisms are called pathogens. The pathogens are usually microorganisms that are parasites causing harm to the host either directly damaging the cells or produce toxins that affect body functions. 2015 STPM
CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases Some people may spread a pathogen even though they do not have the disease themselves. Such people are symptomless carriers. It can ILKPɉJ\S[[V[YHJL[OLTHZ[OL source of an infection. The way in which a pathogen passes from one host to another is called transmission cycle. Infectious diseases can be controlled by breaking the transmission cycle. Info Bio Info Bio 2. The pathogens include viruses, bacteria, fungi, protozoa and flatworms. Mites and ticks can be classified as pathogens too. Viral and bacterial diseases are common and can be distinguishable with antibiotics being able to kill bacteria but not viruses. 3. Infectious disease is transmissible. The disease can be spread from an infected person to an uninfected person. Some diseases can only be spread from one person to another person by direct contact, as the pathogen cannot survive outside the human body. However, some diseases can be transmitted indirectly from person to person by a number of mechanisms: (a) Through air Cold and influenza viruses are carried in the air in tiny droplets of moisture. Every time someone with these illnesses speaks, coughs or sneezes, millions of viruses are propelled into the air. If you breathe in the droplets, you may become infected. (b) Via water Many pathogens, including the virus which causes polio and the bacterial species which causes cholera, are transmitted in water. If we drink untreated water, we run the risk of catching these diseases. (c) In body fluids such as blood or semen For example, HIV virus that causes AIDS can only survive in body fluids and is transmitted by blood or semen. HIV virus is spread by sexual contact, through cuts and open wounds, from mother to baby or through blood transfusion. (d) Through vectors A vector is an organism which carries a pathogen from one host to another. One example of a vector is the mosquito which transmits malaria and dengue. The mosquito injects the pathogens into a person’s blood when it bites. 4. Infectious disease may be passed through symptomless carriers. A well known example is AIDS when even the person who transmits the disease does not know he is a carrier. 5. Infectious diseases are able to cause diseases in animals and/or plants. Malaria parasite is found to infect both human and animals that are both domesticated and wild. A recent example is avian flu virus that can infect birds and humans. 6. Infectious diseases can be controlled by breaking transmission cycle. For example, dengue fever can be controlled by eliminating the mosquito vector. If we get rid of stagnant water preventing Aedes mosquitoes from breeding, we can prevent dengue fever. Types of Infectious Agents 2015 1. Infectious agents are biological agents or pathogens such as a virus, bacterium, fungus or protoctist that causes disease. Example of protoctist includes Plasmodium, a protozoan that causes malaria. )HJ[LYP\Tsingular) )HJ[LYPHplural) -\UN\Zsingular) Fungi (plural) 7YV[VaVHUsingular) 7YV[VaVHplural) )HJ[LYP\Tsingular) )HJ[LYPH plural) -\UN\Z singular) ( ) Language Check Fungi plural) 7YV[VaVHUsingular) 7YV[VaVH plural)
Learning Outcomes CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases 2. Larger infectious agents include flatworms, round worms and mites. Liver flukes are parasites causing parasitic diseases called helminthiasis. Similarly, roundworms that are parasites can cause roundworm parasitic diseases. Ticks and mites are arachnids that can also cause diseases directly on animals. 13.2 Dengue 13.2 Dengue 1. Dengue is one of the infectious diseases that is transmitted by a vector. The vector is mosquitoes in the genus Aedes, which includes a number of mosquito species. Of these species, the primary vector of the dengue is the species Aedes aegypti. It is the principal dengue vector responsible for dengue transmission and dengue epidemics. Other mosquito species in the genus Aedes including Aedes albopictus, Aedes polynesiensis, and Aedes scutellaris have a limited ability to serve as dengue vectors. 2. Aedes aegypti is a small, dark mosquito that can be identified by the white bands on its legs and a silver-white pattern of scales on its body that looks like an ancient Greek musical instrument called a lyre (Figure 13.1). Figure 13.1 Aedes mosquito with stripes 3. Aedes aegypti dwell in tropical and subtropical regions all over the world, mainly between the latitudes of 35°N and 35°S where the winter temperature is no colder than 10°C. They are unable to survive in cold winters because Aedes aegypti require a warm climate. The Causes and Symptoms of Dengue Causes 1. Dengue is transmitted by the bite of an Aedes mosquito infected with any one of the four types of dengue. Students should be able to: (a) describe the causes and symptoms of dengue; (b) explain the transmission of dengue; (c) discuss the roles of social, economical and biological factors in the prevention of dengue. INFO Dengue
CHAPTER 13 fl Biology Term 2 STPM Chapter 13 Infectious Diseases 2. Dengue is caused by Dengue Fever Virus (DENV) which is an RNA virus of the family Flaviviridae; genus Flavivirus. The viruses are transmitted by Aedes mosquitoes (arthropods), and are referred to as arbovirus (arthropod-borne virus). 3. The virus attacks white blood cells including granulocytes and agranulocytes after binding on and entering into to reproduce inside the cells while they move throughout the body. The virus also attacks endothelial and fibroblast cells. 4. The virus causes the infected white blood cells to produce a number of signalling proteins, such as interferon, which are responsible for many of the symptoms, such as the fever, the flu-like symptoms and the muscle and joint pains. Symptoms appear 3—14 days after the infective bite. 5. In later stage, the virus attacks the bone marrow. The dysfunction of the bone marrow leads to reduced numbers of platelets, which are necessary for effective blood clotting and repair of blood capillaries. This leads to petchiae rashes in the skin and purple gum and tongue. Finally, it may lead to lethal haemorrhagic complications. Platelets are directly reduced non-functional by the viruses. 6. The liver may also be attacked causing less plasma proteins to be produced. This causes increase in water potential in the blood vessels and water from the bloodstream leaks through the wall of small blood vessels into body cavities. As a result, less blood circulates in the blood vessels, and the blood pressure becomes so low that it cannot supply sufficient blood to vital organs leading to sudden death. This results in dengue shock syndrome. 7. Dengue fever is a febrile illness that affects infants, young children and adults. 8. There are no specific antiviral medicines for dengue. It is important to maintain hydration. Use of acetylsalicylic acid (e.g. aspirin) and non-steroidal anti-inflammatory drugs (e.g. Ibuprofen) is not recommended. 9. Dengue haemorrhagic fever (fever, abdominal pain, vomiting, bleeding) is a potentially lethal complication, affecting mainly children. Early clinical diagnosis and careful clinical management by experienced physicians and nurses increase survival of patients. Symptoms 1. 80% people infected with dengue virus are asymptomatic or only have mild symptoms such as an uncomplicated fever. 5% have more severe illness and a small proportion have life-threatening complications. The incubation period (time between exposure and onset of symptoms) ranges from 3–14 days, but most often it is 4–7 days. STPM 2013/P2/Q20(a) STPM 2014/P2/Q14
CHAPTER 13 ffi Biology Term 2 STPM Chapter 13 Infectious Diseases 2. Symptoms include fever, headache, muscle and joint pains, and a characteristic skin rash that is similar to measles. There are variations of how the symptoms develop but typically they follow the course of infection. The infection is divided into three phases i.e. febrile, critical, and recovery. 3. The febrile (initial) phase involves high fever, often over 40 °C, and is associated with generalised pain and a headache; this usually lasts two to seven days. At this stage, a rash occurs in 50–80% of those with symptoms. It occurs in the first or second day of symptoms as flushed skin, or later in the course of illness (days 4–7), as a measleslike rash. The fever itself is classically biphasic in nature, breaking and then returning for one or two days. 4. In a small proportion of cases the disease develops into critical phase or the life-threatening dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs. Altered level of consciousness Hypotension Plueral effusion Ascites Headcache Sudden-onset fever Mouth and nose bleeding Muscle and joint pains Vomiting Rash Diarrhea Gastrointestinal bleeding Seizures Itching Slow heart rate Figure 13.2 Schematic depiction of the symptoms of dengue fever 5. The recovery phase occurs next, with reabsorption of the leaked fluid into the bloodstream. This usually lasts two to three days. The improvement is often striking, but there may be severe itching and a slow heart rate. Another rash may occur with either a masculopapular (red flat) or a vasculitic (vessel-like) appearance, which is followed by peeling off the skin. During this stage, a fluid overload state may occur; if it affects the brain, it may cause a reduced level of consciousness or seizures. A feeling of fatigues may last for weeks afterwards. 6. Children often experience symptoms similar to those of the common cold and gastroenteritis (vomiting and diarrhoea), and generally have less severe symptoms than adults, but are more susceptible to the severe complications.
CHAPTER 13 ffl Biology Term 2 STPM Chapter 13 Infectious Diseases 7. In some people, the disease proceeds to a phase which follows the resolution of the high fever and typically lasts one to two days. During this phase there may be significant fluid accumulation in the chest and abdominal cavity due to increased capillary permeability and leakage. This leads to depletion of fluid from the circulation and decreased blood supply to vital organs. 8. During this phase, organ dysfunction and severe bleeding, typically from the gastrointestinal tract, may occur. Shock (dengue shock syndrome) and haemorrhage (dengue hemorrhagic fever) occur in less than 5% of all cases of dengue, however those who have previously been infected with other serotypes of dengue virus (“secondary infection”) are at an increased risk. 9. A decreased level of consciousness occurs in 0.5–6% of severe cases, which is attributable either to infection of the brain by the virus or indirectly as a result of impairment of vital organs, for example, the liver. Infection of the heart and acute liver failure are among the rarer complications. The Transmission of Dengue 1. Female mosquitoes are involved in the transmission of dengue. Male mosquitoes do not bite. The female mosquitoes take blood meals that are used to support the development of eggs. 2. Aedes mosquito prefers to take its meals from humans. Aedes aegypti feeds throughout the day with peaks of activity at mid-morning and late afternoon. 3. The transmission of dengue can be explained as follows: g a f e d b c Figure 13.3 A mosquito taking a blood meal from a human Aedes aegypti mosquito
CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases a When a female mosquito drinks the blood of an infected person, it takes in a certain number of dengue viruses. b The viruses move up with the ingested blood into the oesophagus. c The viruses end up in the stomach where they resist the mosquito’s digestive juices. d The viruses are able to break through the stomach wall barrier and after a latency phase, they multiply with great intensity inside the mosquito’s cells. The virus takes about 5-7 days to replicate itself. e While invading all parts of the mosquito’s body, the virus enters the salivary glands where it concentrates. The mosquito is not affected by the virus. f & g The next time the female A. aegypti bites a healthy person to take a blood meal, it injects saliva that contains dengue virus into the bloodstream of the person. So, the person is infected by the dengue virus. 4. Dengue can also be transmitted via infected blood products and through organ donation. In countries such as Singapore, where dengue is endemic, the risk is estimated to be between 1.6 and 6 per 10, 000 transfusions. 5. Vertical transmission (from mother to child) during pregnancy or at birth has been reported. The virus can be passed from the mother’s blood into the child’s blood. Other person-to-person modes of transmission have also been reported, but are very unusual. Roles of Social, Economical and Biological Factors in The Prevention of Dengue Social factors 1. Social factors involve the health authority and the community. Factors involved are: (a) Collaboration between the health and other sectors (public and private). (b) Advocacy, social mobilisation, legislation and enforcement. 2. Literacy level of the population determines the success of the prevention. It also determines the cooperation with the health authority. This factor explains why dengue is more rampant in developing countries in Africa. Poor understanding of the transmission leads to not taking efforts on preventions. 3. Public education through advertisements in mass media, campaigns to inform about Aedes breeding and mode of transmission are necessary in the prevention. Individuals or community at large should be adequately informed and conscious to clear the environments of breeding grounds especially immediately after rain. The response of the community determines the success of prevention of dengue.
CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases 4. More inspections for mosquito breeding sites by the community can prevent dengue. Walkabouts can be organised by the government or private sector to check the neighbourhood of breeding grounds. 5. Storing of water due to poor water supply is a social factor. The higher rates found in rural areas in Thailand are linked to a higher dependence on water storage during the dry season. Increase in dengue fever among rural populations has also been observed in Central and South America, with similar prevalence rates in some urban and rural populations. Mosquito breeding is highly dependent on the existence of man-made artificial containers or the presence of stagnant water for the Aedes mosquito to breed. 6. Solving water supply problem by the government in rural areas so that water needs not have to be stored creating mosquito breeding sites. This situation also must be analysed not only from the individual perspective but also as a social problem where every member of the community has a role and a responsibility not to create mosquito breeding site. 7. Improved housing with mosquito screens in doors and windows and the use of air conditioning greatly reduce transmission rates. Housing with reliable water supply with no requirement for extra water storage can prevent dengue. 8. Increase in population density in urban areas is another factor. Aedes aegypti is an urban mosquito that is domesticated. Human ignorance in container disposal, domestic unconscious creation of water storage in gardening plates and increased construction sites are causing continuous production of mosquito breeding sites. These sites that are in close proximity to dwellings provide ideal conditions for mosquito breeding and dengue transmission. 9. More migration and global movement provide natural sources for dengue virus dispersion. Cities are better communicated by more and faster means of transport, thereby creating urban networks where risks are easily disseminated from local to international settings. Population movements including migration and tourism are vehicles for spreading the serotypes and strains, and the co-circulation of multiple serotypes increases the potential for the emergence of dengue hemorrhagic fever or dengue shock syndrome. 10. Strict enforcement must be carried out; first to inform, then to inspect Aedes breeding sites and finally to enforce legislation against their breeding both in residential and industrial premises. Health authorities in most countries are empowered by legislation to enforce regulations in vector control. Owners of premises found to breed Aedes are fined. Legislation or by-laws are already enforced in most counties.
CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases Economical factors 1. One of the economical factors involved in the prevention of dengue are financing the preventive programmes. Though poor and rich countries are equally infested with dengue, stronger economies are better off in carry out prevention. 2. Huge amount of money is required by the central government to finance the health department, universities and private organisation to carry out preventive measures. Little gains in the results is seen. The investment only pays in long term. So far little research is done on prevention by vaccination. Low financial allocation on these aspects discourages many researchers. 3. Researches require finance to seek hard evidence on the various serotypes of viruses that are involved, the effects of each type and how well to control the mosquito vectors, the resistance to insecticides and larvicides. As dengue has become pandemic, many pharmaceutical companies are spending much to develop drugs that can prevent dengue outbreak. 4. Municipalities need allocations to inspect and to control Aedes breeding in abandon areas. The intense inspection and penalty in Malaysia has seen results in informing the public that getting rid of mosquito breeding grounds can reduce dengue tremendously. Residential breeding grounds have since reduced but in construction sites and wild areas, more inspections need to be done. 5. Many private enterprises are willing to contribute financially to prevent dengue in their own premises. This is a good inter-agency collaborations in most counties especially in Malaysia. If workers get dengue, not only the companies face greater financial loss in production, they have to face the laws and serious loss in public confidence. 6. Most countries are willing to pay a small financial investment on prevention to prevent greater economical loss later. Most non-fatal cases of dengue involve at least a few days to a week of hospitalisation or rest to recover. This incurs economic loss to the country production and manpower wastages. An uncontrolled outbreak might have disastrous consequences in some economies. 7. Health authority require finance to carry out its preventive programmes and management of dengue. Clinicians require finance on dengue diagnosis and immediate actions to prevent further outbreak. Laboratory infrastructure, surveillance systems on prevention and control strategies require finance. 8. As developing countries improve in their economic status like South East Asian countries, the outbreak of dengue is generally improved over the years. Better housing with mosquito screens and air conditioning
CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases reduces contact with mosquitoes. More inspections and enforcement on various measures have already paying results. The focus now is on poor nations that are now facing the worse of dengue outbreaks. Biological Factors 1. Biologically dengue cannot be prevented through vaccination as there are no effective vaccines developed against the dengue virus. This is due to viral genome mutates constantly and the viral coat antigens keep on changing, so the immune system cannot recognise the ever changing antigens. 2. One biological prevention depends on control of and protection from the bites of the mosquito that transmits dengue virus. The World Health Organization recommends an Integrated Vector Control program consisting of five elements: (a) Advocacy, social mobilisation and legislation are enforced to ensure that public health bodies and communities are strengthened. (b) Collaboration between the health and other sectors (public and private) are jointly required. (c) An integrated approach is used to control disease and to maximise use of resources. (d) Evidence-based decision making by health authority is required to ensure any interventions are targeted appropriately. (e) Capacity-building by government is required to ensure an adequate response to the local situation. 3. Government’s integrated approach is required for effective prevention and final elimination of dengue. The Malaysian Ministry of Health’s Vector Borne Disease Control Section carries out the following strategies to control dengue fever. (a) Epidemiological surveillance through prompt case notification within 24 hours of clinical diagnosis via phone, fax or e-mail. (b) Enhancing laboratory diagnostic support through the use of rapid screening tests and confirmation by standard laboratory technique. (c) Improved clinical management through early case detection and quality assurance surveillance and audit. (d) Case control through rapid response aimed at case investigation and destruction of mosquitoes by chemical fogging. (e) Entomological surveillance through regular Aedes larval surveys. (f) Legislative control on Aedes breeding through premises inspection and destruction of breeding sources. (g) Public education through health education activities in the community and with community involvement. (h) Inter-agency collaboration targeting at high-risk areas and population groups such as schools, construction sites, solid-waste dumps, factories and government facilities. STPM 2013/P2/Q20(b)
Learning Outcomes CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases Students should be able to: (a) describe the causes and symptoms of cholera; (b) explain the transmission of cholera; (c) discuss the roles of social, economical and biological factors in the prevention of cholera. Figure 13.4 Vibrio cholerae as observed under electron microscope 4. For the general public, the primary method of controlling A. aegypti is by eliminating its habitats where the mosquito lays her eggs within and outside buildings. This is done by emptying containers of water or by adding Abate larvicide or biological control agents e.g. predators of larvae to stagnated water after raining. 5. Spraying insecticide to kill the adult females is also effective. This is done by the ministry of health immediately after case of outbreak being reported. This is more effective when water-based pyrethroid insecticide fogging formulations such as Resigen or Aqua-resigen is used when people may be more willing to open their houses to be sprayed compared with diesel-based insecticide. 6. People can prevent mosquito bites by wearing clothing that fully covers the skin, using mosquito netting while resting, and/or the application of insect repellent (DEET being the most effective). Mosquito bite is the only way the dengue virus can enter our body. 13.3 Cholera 13.3 Cholera 1. Cholera is an infection in the small intestine caused by the bacterium Vibrio cholerae which causes profuse, watery diarrhoea and vomiting. 2. It is endemic in parts of Asia, particularly India. In 1991 more than 16 000 people died worldwide from half a million cases of cholera. Improved treatment has reduced the death rate dramatically, but it is still a serious disease. The Causes and Symptoms of Cholera Causes 1. Cholera is caused by bacterium Vibrio cholerae (Figure 13.4). This comma-shaped motile bacterium can live in the gut of animals and also any natural environment. 2. The main source of infection is contaminated drinking water by faeces from a sufferer of the disease or a ‘carrier’. A carrier is an individual infected with vibrios who does not develop the typical symptoms of cholera. 3. Vibrio cholera multiplies in the intestine, releasing a powerful toxin called choleragen, which disrupts the functions of the epithelium so that salts and water leave the blood causing severe diarrhoea. The organisms can only multiply and flourish in the human intestine, although they can survive outside of the body. 2013/P2/Q15 2014/P2/Q20(b) STPM
CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases Symptoms 1. The main symptom of the disease is severe diarrhoea due to irritation of the bowel by toxins from Vibrio. The liquid of the faeces looks like rice water and may have a fishy odour. Abdominal pain and vomiting are also common symptoms of the disease. 2. These symptoms usually start suddenly, one to five days after ingestion of the bacteria. However, some people are asymptomatic even if they get the infection. 3. Untreated patient’s skin will turn a bluish-grey colour, while wrinkled hands and sunken eyes occur due to poor skin turgor from extreme loss of fluids. Much of the body water is lost in vomiting or diarrhoea. Dehydration is rapid and quickly results in death unless rehydration treatment is given. 4. Besides, the patient will have a rapid pulse and low blood pressure. This is due to the lack of water in the body. An untreated person with cholera may produce 10–20 litres of diarrhoea a day. 5. Deaths are usually caused by rapid dehydration and electrolyte imbalance. Some may become comatose as the brain cells cannot function in low water potential. The Transmission of Cholera 1. Cholera is a water-borne disease transmitted by water, food or their containers contaminated with cholera bacteria. 2. In developing contries, especially those without sewage treatment or clean water, the main source of infection is water. Infected people, three-quarters of whom may be symptomless carriers, pass out large numbers of bacteria in their faeces. If these untreated faeces contaminate the water supply, then bacteria are transmitted to uninfected people when they drink contaminated water or use the contaminated water to wash food or utensils. If the faeces are not collected or disposed of hygienically, then one patient can infect a wide area of a community. 3. In the developed countries, seafood is the usual cause of cholera. Seafood, especially filter-feeders such as oysters and mussels, become contaminated because they concentrate cholera bacteria when sewage is pumped into the sea. The disease probably spreads through contaminated seafood if fish and shellfish are eaten raw. 4. Cholera can be spread by houseflies contaminated with cholera bacteria. The poor sanitary conditions and the increase in population of flies are perfect conditions for the spread of the disease. VIDEO Cholera
CHAPTER 13 Biology Term 2 STPM Chapter 13 Infectious Diseases 5. Cholera may be spread through food or drink contaminated with cholera bacteria if infected people handle food or cooking utensils without washing their hands. This is transmitted especially through asymptomic infected person. 6. Cholera rarely spreads directly from person to person. The amount of bacteria sneezed out or carried by droplets during spitting may be too small to cause infection but caution should be taken to cover the mouth of patients. The Roles of Social, Economical and Biological Factors in the Prevention of Cholera Social Factors 1. Public education is necessary for effective prevention of cholera in both endemic and non-endemic countries. This is especially in undeveloped countries and the campaign of educating depends on the social service of WHO. In developed countries, seafood especially shell fish are possible to transmit cholera if eaten not fully cooked. The public must be informed in time of cholera outbreak. 2. Cholera is prevented by boiling, filtering or chlorination of water before use. Boiling, filtering and chlorination can kill cholera bacteria in water. Cholera is no longer considered an issue in Europe, North America and many countries due to filtering and chlorination of the water supply. Social and economical advancement in these countries greatly reduce the outbreak of cholera. 3. Building water treatment plants is a social requirement of any government to prevent cholera. Such plants should never be contaminated with cholera bacteria. This may however, occur in time of wars or natural disasters in poorly maintained plants as dead bodies in water catchment areas can cause dormant cholera bacteria to breed easily. Bottled filtered water should be provided to the victims. 4. Drinking water piped into homes becomes a necessity to prevent cholera in modern homes. Out of town residents should be installed with properly treated piped water. Drinking water should be piped from properly treated plants. It is advisable not to drink untreated water from natural sources. 5. Surveillance and prompt reporting enable cholera epidemics to be controlled rapidly. Cholera exists as a seasonal disease in many endemic countries, occurring annually mostly during rainy seasons. Surveillance systems can provide early alerts to outbreaks, leading to effective coordinated response to contain the outbreak. Understanding the timing and location of outbreaks provide guidance for improving cholera control activities by the national health authorities. 2015 STPM
CHAPTER 13 fl Biology Term 2 STPM Chapter 13 Infectious Diseases Learning Outcomes Students should be able to: (a) describe the causes and symptoms of [\ILYJ\SVZPZ;)" (b) explain the transmission VM;)" (c) discuss the roles of social, economical and biological factors in the WYL]LU[PVUVM;) Economical Factors 1. Economically advanced countries are always better educated in preventing cholera. The public are better informed and more aware of cholera transmission. 2. Economically better countries have better facilities for water treatment and sewage disposal systems. There is very little chances of cholera bacteria contamination in water and food. 3. Economically better countries have better health and medical facilities. They have high health standard in handling of food. They have better medical facilities and personnel to take actions of prevention and cure. Biological Factors 1. Cholera can be prevented by breaking the transmission cycle of the cholera bacteria in the event of an outbreak. This is done by a safe sewage disposal system with no possibility of contamination of cholera bacteria into the drinking water supply system. There should be no possibility of any vomited bacteria getting to the water supply too. 2. Early treatment of patients is also a way to get rid of the cholera bacteria. Antibiotics are used in most cases as intestinal bacteria can be easily killed. Recent development of resistant strains is common. Treatment to save lives is by oral or intravenous hydration therapy to replace glucose and salts or electrolytes lost. Absorption of salts helps to absorb glucose, thus increases water uptake by osmosis. 3. A few safe and effective oral vaccines are available to prevent cholera. An example is Dukoral, an orally administered, inactivated whole cell vaccine. Another vaccine is intravenous vaccine that is effective for two to three years. The World Health Organization (WHO) recommends immunisation of high risk groups, such as children and people with HIV, in countries where this disease is endemic. 13.4 Tuberculosis (TB) 13.4 Tuberculosis (TB) 1. Tuberculosis (TB) is an infectious lung disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. It produces persistent cough, loss of weight and death if left untreated. 2. TB has been the cause of millions of deaths. Also known as consumption, it is especially prevalent in poorer families who are suffering from malnutrition and overcrowding.
CHAPTER 13 ffi Biology Term 2 STPM Chapter 13 Infectious Diseases The Causes and Symptoms of TB Causes 1. The main cause of TB is the bacterium Mycobacterium tuberculosis, a small, aerobic, non-motile bacillus. Mycobacterium is a bacterial parasite that penetrates cells, preventing the defence mechanisms of the body from finding it. 2. Mycobacterium tuberculosis is a slow-growing aerobic bacterium that divides every 16 to 20 hours. Therefore, it has an extremely slow rate of cell division compared with other bacteria, which usually divide once in less than an hour. 3. There are other species of Mycobacterium that can cause TB especially in Africa. One species found in the cow is Mycobacterium bovis, but this species has almost being eliminated after milk is pasteurised before consumption. 4. TB commonly affects the lungs so breathing is made difficult depending on the stage of infection. The bacteria live inside the alveolar cells and also cells of the air passage. The cells of the air sacs and small bronchioles will die and typically produce empty spaces (cavity) in the lungs as shown in X-ray radiograph (Figure 13.6). The infection may erode into the pulmonary artery, resulting in massive bleeding (called Rasmussen’s aneurysm). Tuberculosis may become a chronic illness and cause extensive scarring in the upper lobes of the lungs. Symptoms 1. The symptoms of TB include chest pain and typical prolonged cough of more than three weeks duration. About 25% of people may not have any symptoms (i.e. they remain “asymptomatic”). The cough is caused by extra mucus produced and damaged cells cause irritations in the lungs. Occasionally, people may cough up blood in small amounts. 2. Systemic (general) symptoms include fever, chills, night sweats, appetite loss, weight loss and easy fatigability. Only 5 - 10 % of healthy people if infected with TB will develop active disease during their lifetime. 30% of those infected with HIV develop active disease because of their poor immune response. 3. Other symptoms outside the lungs affecting the pleural membrane that surround the lungs, central nervous system, lymphatic systems, urino-genital system and bones may be affected. The cells and tissues in the systems will be attacked by the TB bacteria. In about 15–20% of active cases, the infection spreads outside the respiratory organs. These are collectively known as “extra-pulmonary tuberculosis”. There are many variations to the symptoms both within and outside the lungs. Figure 13.5 Mycobacterium tuberculosis Figure 13.6 Chest X-ray of a person with advanced tuberculosis. Arrow points to a cavity in patient’s right upper lobe. 2014/P2/Q15 STPM VIDEO Tuberculosis
CHAPTER 13 ffl Biology Term 2 STPM Chapter 13 Infectious Diseases The Transmission of TB 1. TB is spread by aerosol droplets of 0.5 to 5.0 μm in diameter. When people with active pulmonary TB cough, sneeze, speak, sing, or spit, they expel infectious aerosol droplets. A single sneeze can release up to 40, 000 droplets. Each one of these droplets may transmit the disease, since the infectious dose of tuberculosis is very low. The inhalation of fewer than 10 bacteria may cause an infection. 2. Poor or dense housing encourages transmission of TB. This is due to the close proximity of individuals that enable aerosol droplets to easily spread from the infected to others. Therefore, the chance of transmission is always very high in poor countries or among immigrants in the cities that stay in crowded housing. 3. Low protein diets linked to lowered immunity especially in developing countries increases the transmission of TB. People who are malnourished have greater chance of having active TB. The immune system is compromised due to a low protein diet. 4. Late diagnosis encourages the development of TB into the advance stage and increases transmission to more people. This occurs in countries with poor or sub-standard medical facilities. Mycobacterium by nature grows very slowly and the incubation is very long resulting in the spread of the disease before the patient is discovered to be infected. 5. Lack of vaccination also encourages TB bacteria to be developed and then transmitted. Countries with BCG vaccination against TB have almost eliminated TB. Malaysia in the 1990s had no TB patients but in the last ten years, TB has recurred due to it being brought in by foreign immigrants. 6. Antibiotics not available or no effective antibiotics to use are another cause of transmission. This is a third world problem. Poor countries need the World Health Organisation to help to supply free medicines. If no effective antibiotic is used, this can also bring about the development of antibiotic resistant strain. 7. Medical services not available in rural areas and in poor countries. In large countries like China or in Africa, medical service is poor in isolated villages. An infection of one individual can result in the spreading of the disease to the whole village or nearby villages. There is no facility for isolating people in the rural areas too, resulting uncontrolled spreading of the disease. 8. Transmission is encouraged by immunosuppressive drugs, substance abuse or AIDS. TB occurrence is positively correlated to high incidence of drug abuse and AIDS. This occurs even in the city of London where there is an increase of TB from foreign immigrants whose immune system is compromised by drug abused or AIDS. TB also has high occurrence in isolated villages in Africa.
CHAPTER 13 fl Biology Term 2 STPM Chapter 13 Infectious Diseases 9. Resurgence of tuberculosis is also due to drug-resistant strains of TB. Recent research has found that there are highly antibiotic resistant strains of Mycobacterium in the US and India. Such strains cannot be killed by normal TB antibiotics. 10. Lack of testing of milk had one time encouraged transmission of Mycobacterium bovis. This strain of TB is very common in cattle rearing countries including US, UK and New Zealand. This Mycobacterium can survive in other animals making transmission easily passed to humans. The incidence of this bacterium has been very low after milk is pasteurised before consumption. The Roles of Social, Economical and Biological factors in the Prevention of TB Social Factors 1. Public education on the nature and transmission of TB can help in the prevention. In Malaysia, people should be reminded not to harbour illegal immigrants who may show signs of TB infection. This can bring about spreading the disease first to members of the family and then to people at large in the community. In India, million of people are still harbouring the TB bacteria. It will take time for people to understand the mode of transmission and adjust their lifestyle to curb the spreading of the bacteria. In China that have high incidence of TB in the past, the people are educated enough to curb the spreading. TB is found in isolated places and certain pockets in the cities. 2. Government effort and especially public health department plays an important role in the prevention of TB. An example is in China. The spread of severe acute respiratory syndrome (SARS) in 2003, brought to light substantial weaknesses in the China’s public health system. After the SARS epidemic was brought under control, the government increased its commitment and leadership to tackle public health problems. 3. Legislation to make it an offence to stay overcowded in a house can prevent the spread of TB. This is especially relevant for immigrants from TB endemic countries like India. TB is found to be present in overcrowded housing areas even in London. 4. Stricter screening and regular checks on TB carriers can also lower the incidence of TB from immigrants. Due to high mobility of travellers, there is certain difficulty to detect carriers. Biological Factors 1. Antibiotics are commonly used to rid the body of the TB bacteria so that the bacteria are prevented from spreading. Antibiotics most commonly used are rifampicin (also known as rifampin in United
CHAPTER 13 fl Biology Term 2 STPM Chapter 13 Infectious Diseases States) and isoniazid to kill the TB bacteria. The treatments can be prolonged, taking several months to more than a year. Latent TB treatment usually employs a single antibiotic, while active TB disease is best treated with combinations of several antibiotics to reduce the risk of the bacteria developing into antibiotic resistant strains. People with latent infections are also treated to prevent them from progressing to active TB disease later in life. 2. People with TB and their contacts (contact tracing) are identified and then treated. This can be a tedious process as the people in today’s world are very mobile unlike those of past years. In Malaysia, the newly infected are those of foreign immigrants or those who had come in close contact with them. This makes difficult with the large influx of illegal immigrants who are potential points of spreading the TB bacteria. 3. BCG vaccine as part of their TB control programs is already carried out for many decades. Vaccination of BCG was very successfully done in Malaysia to all primary school students and later to all newly born free of charge. TB has become uncommon in our country and BCG vaccination is administered to the newborns. In Canada, the United Kingdom, and the United States, part of the reasoning arguing against the use of the vaccine is that it makes the tuberculin skin test falsely positive, and therefore, of no use in screening. A number of new vaccines are currently in development. Economic Factors 1. Increase funding for the health department can prevent most infectous diseases including TB. China implemented the world’s largest internetbased disease reporting system to improve transparency, reach and speed, and started a programme to rebuild local public health facilities and national infrastructure. This effort has brought about a great jump in the successes of controlling TB in particular. 2. Improved economy improves housing. This will decrease the spread of TB bacteria from carriers. As TB is spread in aerosol breath out from carrier, the carrier may die without spreading to other if he stays in better ventilated housing. 3. Improved economy will enable the sick to seek medical help earlier. Better standard of living will improve the immunity of people against TB. 4. Improved economy will enable government to improve medical services. In most countries, compulsory free immunisation programme against certain infectious diseases is carried out. This can greatly reduce TB.
Learning Outcomes CHAPTER 13 fl Biology Term 2 STPM Chapter 13 Infectious Diseases 13.5 Malaria 13.5 Malaria 1. Malaria is an infectious disease caused by a protist (protozoan) of the genus Plasmodium. The protists first infect the liver then attack the red blood cells, causing symptoms that typically include fever alternating with chill, progressing to coma or death. 2. The disease is one of the world’s biggest killers. Up to 500 million people have malaria every year. It is widespread in tropical and subtropical countries including much of Sub-Saharan Africa, Asia, and the Americas. The Causes and Symptoms of Malaria Causes 1. Malaria is caused by protozoa parasites that are members of the genus Plasmodium (phylum Apicomplexa). In humans, malaria is caused by P. faciparum, P. malariae, P. ovale and P. knowlesi. Among those infected, P. falciparum is the most common species identified (about 75%) followed by P. vivax (about 20%). P. falciparum accounts for the majority of deaths. P. vivax proportionally is more common outside of Africa. 2. Malaria infection develops in two stages: first infect the liver then attack the red blood cells. (a) Infecting the liver When an infected female Anopheles mosquito injects saliva into before sucking up blood, sporozoites in its saliva enter the bloodstream. They move to the liver where they infect the liver cells called hepatocytes. There, the parasites reproduce asexually and asymptomatically for a period of 8–30 days. After this period in the liver, these sporozoites differentiate to become thousands of merozoites. They rupture their host cells to enter into the blood and infect red blood cells to begin the erythrocytic stage of the life cycle. They are not attacked by the immune system as they are wrapped up by the cell membrane of the infected host liver cell. (b) Attacking the red blood cells Within the red blood cells, the parasites reproduce further asexually, periodically breaking out of their host cells to invade fresh red blood cells. This breakout occurs cyclically and gives rise to the classical descriptions of waves of chill from simultaneous waves of merozoites escaping in the midst of high fever. 3. Some P. vivax sporozoites do not immediately develop into merozoites in the liver but instead produce hypnozoites that remain dormant for periods ranging from several months (6–12 months is typical) to as Students should be able to: (a) describe the causes and symptoms of malaria; (b) explain the transmission of malaria; (c) discuss the roles of social, economical and biological factors in the prevention of malaria. INFO VIDEO Malaria Malaria
CHAPTER 13 fl Biology Term 2 STPM Chapter 13 Infectious Diseases long as three years. After a period of dormancy, they reactivate and produce merozoites. Hypnozoites are responsible for long incubation and late relapses in P. vivax infections. 4. The parasite is usually protected from attack by the body’s immune system because for most of its human life cycle it stays in the liver and blood cells so they are not detected by immune system. However, circulating infected blood cells are destroyed in the spleen. To avoid this fate, the P. falciparum parasite displays adhesive proteins on the surface of the infected blood cells, causing the blood cells to stick to the walls of small blood vessels, thereby preventing the parasite from going through the spleen. The blockage of the blood vessels causes symptoms such as in placental and cerebral malaria. In cerebral malaria, the blockage by the red blood cells can cause embolic stroke leading to coma. 5. Although the red blood cell surface has antigens of P. falciparum, the immune system cannot get rid of the infected cells. This is because they are too many variations in the antigens and these variations keep on changing. 6. Pregnant women infected with malaria usually has stillbirths, high infant mortality and low birth weight, particularly in P. falciparum infection, but also in other species infection, such as P. vivax. Symptoms 1. The symptoms of malaria may include fever, shivering, flu like illness, arthralgia (joint pain), vomiting, haemolytic anaemia, jaundice, haemoglobinuria, retinal damage, and convulsions. The symptoms typically begin 8–25 days following infection. However, symptoms may occur later in those who have taken anti-malarial medications as prevention. 2. The classic symptom of malaria is cyclical occurrence of sudden coldness followed by rigour and then fever and sweating lasting about two hours or more. This occurs every two days in P. vivax and P. ovale infections, and every three days for P. malariae. P. falciparum infection can cause recurrent fever every 36–48 hours or a less pronounced but almost continuous fever. 3. Children with malaria frequently exhibit abnormal posturing that indicates severe brain damage. Cerebral malaria is associated with retinal whitening, which may be a useful clinical sign in distinguishing malaria from other causes of fever. 4. Splenomegaly (enlarged spleen), severe headache, cerebral ischemia (oxygen deficiency in cerebrum), hepatomegaly (enlarged liver), hypoglycemia, and haemoglobinuria with renal failure may occur in severe cases. Renal failure is a feature of black water fever, where haemoglobin from lysed red blood cells leaks into the urine.
CHAPTER 13 fl Biology Term 2 STPM Chapter 13 Infectious Diseases 5. In severe cases, coma potentially leading to death especially in young children and pregnant women. This is usually caused by P. falciparum, and typically arises 6–14 days after infection. Non-falciparum species have however been found to be the cause of about 14% of cases of severe malaria in some groups. The Transmission of Malaria Infective stages of parasite enter bloodstream and then liver cells Liver Mosquito takes infected blood meal Male and female gametes fuse in mosquito’s stomach 6 – 12 days Cell division produces thousands of immature malarial parasites Infective stage of parasite invade mosquito’s salivary glands 24 hours Maturation and production of parasite’s male and female sex cells (gametes) 48 – 72 hours Infected mosquito takes blood meal Parasites leave liver cells and enter red blood cells d e g h a b c f Figure 13.7 The transmission of Malaria by Plasmodium 1. The parasites are transmitted by female mosquitoes of the Anopheles genus, which feed on human blood to obtain the protein they need to develop their eggs. 2. Figure 13.7 shows the life cycle or transmission of Plasmodium. The parasite has two hosts: the sexual stage occurs in mosquitoes, the asexual stage in humans. (a) Female Anopheles mosquitoes take up some of the pathogen’s gametes with the blood meal if they bite person with malaria. (b) These gametes fuse and develop in the mosquito’s gut to form infective stages. (c) This produces an ookinete that penetrates the gut lining and produces an oocyst in the gut wall. When the oocyst ruptures, it releases sporozoites that migrate through the mosquito’s body to the salivary glands. 2013/P2/Q14 STPM
CHAPTER 13 fl Biology Term 2 STPM Chapter 13 Infectious Diseases (d) When the mosquito feeds again, it injects an anticoagulant that prevents the blood meal from clotting so that it flows out of the human into the mosquito. The infective stages pass out into the blood together with the anticoagulant in the saliva, and the parasites enter the red blood cells, where they multiply. 3. The sporozoites are injected into the skin, alongside saliva, when the mosquito takes a subsequent blood meal. The sporozoites enter the bloodstream, and migrate to the liver. They infect liver cells, where they multiply into merozoites, rupture the liver cells, and return to the bloodstream. Then, the merozoites infect red blood cells, where they develop into ring forms, trophozoites and schizonts that in turn produce further merozoites. 4. Only female mosquitoes feed on blood; male mosquitoes feed on plant nectar, and thus do not transmit the disease. The females of the Anopheles genus of mosquito prefer to feed at night. They usually start searching for a meal at dusk, and will continue throughout the night until taking a meal. 5. Malaria parasites can also be transmitted by blood transfusions, although this is rare. This is possible when someone with asymptomatic malaria donated blood and the parasites are not treated to be killed. 6 Malaria can be transmitted by blood sucking bats in the Caribbean and South America. Like mosquitoes, the bats allow the parasites to multiply in the gut and move up to the salivary glands. During biting, the bats inject saliva which carries the parasite into the victim infecting it with the parasite. 7. Malaria recurs after treatment for three reasons. Recurrence occurs when parasites are not cleared by treatment. Re-infection indicates complete clearance but with new infection established from a separate infected mosquito bite. Relapse is specific to P. vivax and P. ovale that involve re-emergence of blood-stage parasites from latent parasites (hypnozoites) in the liver. The longest incubation period reported for a P. vivax infection is 30 years. Approximately one in five of P. vivax malaria cases in temperate areas involves overwintering by hypnozoites, with relapses beginning the year after the mosquito bite. The Roles of Social, Economical and Biological Factors in the Prevention of Malaria Social Factors 1. Public health education strategies promoting awareness of malaria and the importance of control measures have been successfully used to reduce the incidence of malaria in some areas of the developing world. Recognising the disease in the early stages can stop the disease from becoming fatal. Education can also inform people to cover
CHAPTER 13 fl Biology Term 2 STPM Chapter 13 Infectious Diseases over areas of stagnant, still water, such as water tanks that are ideal breeding grounds for the parasite and mosquito, thus cutting down the risk of the transmission between people. There are one to three million deaths annually, mostly among young children in Sub-Saharan Africa. Economic impact-health care cost, working days are lost due to sickness, days lost in education, decreased productivity due to brain damage from cerebral malaria, and loss of investment and tourism spur better public education in pursuit of malaria eradication. 2. Community participation in getting rid of mosquito breeding grounds. Open containers and stagnant water in both private and public places need the cooperation of the public to get rid of them. 3. Legislation against mosquito breeding and stricter checks will prevent malaria outbreak. However, poor countries in tropical Africa and South America are facing vast jungle ground to prevent mosquito breeding. 4. Many countries take measures to reduce import of malaria owing to extensive travel and migration. The presence of malaria in an area requires a combination of high human population density, high mosquito population density and high rates of transmission from humans to mosquitoes and from mosquitoes to humans. If any of these is lowered sufficiently, the parasite will eventually disappear from that area, as happened in North America, Europe and much of the Middle East. However, unless the parasite is eliminated from the whole world, it could become re-established if conditions revert to a combination that favours the parasite’s reproduction. Economical Factors 1. Increase funding to health department so that more personnel are involved. Better medical services will cut down Malaria outbreak. 2. Better economy will improve housing that prevent mosquito entering. Unlike dengue, malaria parasite is more rural based. When rural people keep away from mosquito, the outbreak of malaria is greatly reduced. 3. More funding on prevention is more effective in malaria control. Many researchers argue that prevention of malaria may be more costeffective than treatment of the disease in the long run, but the capital costs required are out of reach of many of the world’s poorest people. There is a wide disparity in the costs of control and elimination programs between countries. For example, in China the government spent a small percentage of health budget in 2010 to pursue malaria elimination in the Chinese provinces. In contrast, a similar program in Tanzania would cost an estimated one-fifth of the public health budget.
CHAPTER 13 flfl Biology Term 2 STPM Chapter 13 Infectious Diseases Biological Factors 1. Malaria can be prevented by vector control. Malaria can be eradicated by eliminating mosquitoes in different ways. (a) One way was by insecticide DDT in the United States and southern Europe. This vector control programs were done in conjunction with the monitoring and treatment of infected humans effectively eliminated it from those regions. (b) In some areas, the draining of wetland breeding grounds and better sanitation were adequate. In tropical areas like Brazil and Egypt, malaria is greatly reduced by removing or poisoning the breeding grounds of the mosquitoes. For example, aquatic habitats of the larva stages are known to have applied with the highly toxic arsenic compound. (c) A more targeted and ecologically friendly vector control strategy involves genetic manipulation of malaria mosquitoes. Transgenic mosquitoes of decreased lifespan, more resistant to the malaria parasite and sterile males mosquitoes are reared and released to reduce the parasite. (d) Indoor residual spraying of insecticides on the interior walls of homes in malaria-affected areas is to kill mosquitoes before they can bite another victim and transfer the malaria parasite. 2. Mosquito nets help keep mosquitoes away from people and significantly reduce infection rates and transmission of malaria. The nets are not a perfect barrier and they are often treated with an insecticide designed to kill the mosquito before it has time to search for a way past the net. Insecticide-treated nets are estimated to be twice as effective as untreated nets and offer greater than 70% protection compared with no net. 3. Other interventions for the control of malaria include mass drug administrations and intermittent preventive therapy. Treatment is usually done using quinine and Chloroquine. Figure 13.9 Mosquito nets create a protective barrier against malaria-carrying mosquitoes that bite at night. Figure 13.8 Man spraying insecticide DDT to protect against mosquitoes carrying malaria
CHAPTER 13 flffi Biology Term 2 STPM Chapter 13 Infectious Diseases Objective questions 1. A child has a high fever of 40.5o C, red rashes and low platelet count. Which of the followings is the cause of the fever? A Paramyxovirus B Parvovirus C Retrovirus D Flavivirus 2. Which of the followings are the symptoms of the first infection of dengue virus? I Temperature of the body falls below normal with profuse sweating II Hemorrhagic patches in skin, gums and gastrointestinal tract III High fever, muscle and joint aches IV Body rashes A I and II B I and III C II and IV D III and IV 3. Which of the followings is correct about dengue? I The level of lymphocytes increases II Shivering and diarrhoea III The level of platelets in the body decreases IV May cause the leakage of fluid from blood vessels A I and II B I and III C II and III D III and IV 4. Which combination is true about tuberculosis disease? Causative agent Mode of transmission A Virus Waterborne B Virus Airborne C Bacteria Waterborne D Bacteria Airborne 5. Which disease is true of its causative agent and method of infection? Disease Causative agent Method of infection A cholera bacterium ingestion B HIV/AIDS virus water-borne C malaria bacterium blood transfusion D tuberculosis (TB) virus inhalation 6. What are the causative agents responsible for cholera, malaria and TB? Cholera Malaria TB A bacterium bacterium virus B bacterium eukaryotic parasite bacterium C eukaryotic parasite virus bacterium D virus eukaryotic parasite virus 7. An area has improved its supply of clean water, sewage treatment, insect control and milk pasteurisation. Which disease, present in the village, will not be reduced by these measures? A AIDS C Malaria B Cholera D Tuberculosis (TB) 8. Which area of the diagram refers to characteristics that are common to both cholera and tuberculosis? Bacterial Infectious Transmitted by water A D C B 9. For which disease is vaccination the most successful method of prevention? A AIDS C Malaria B Cholera D Tuberculosis (TB) STPM PRACTICE 13
CHAPTER 13 flffl Biology Term 2 STPM Chapter 13 Infectious Diseases 10. In parts of a big city, there is an increase in the number of cases of tuberculosis (TB). Which factor is most likely to have contributed to this? A Increased air pollution B Increased drug abuse C Increased pathogen mutation rate D Overcrowded accommodation 11. Which explains why people infected with malaria and people infected with tuberculosis can both live in northern Europe, but only tuberculosis can be passed on to other people there? A Antibiotics can be used to cure people with tuberculosis. B Migrant workers can carry the diseases with them. C Anopheles mosquitoes only breed in subtropical and tropical areas. D Tuberculosis bacteria cannot survive in sub-tropical and tropical areas. 12. The diagram below shows a type of microorganism that can cause disease. Which of the followings disease is caused by this microorganism? A Malaria C Cholera B Dengue D Tuberculosis 13. The antibiotic streptomycin is now proving to be less effective in reducing the incidence of tuberculosis worldwide. What is the reason for this observation? A Antibiotics such as streptomycin are not effective as antiviral drugs. B There is an increase in the number of people infected with drug resistant strains. C Fewer people are living in isolated rural areas and overcrowding occurs in inner cities. D The incidence of HIV infection is increasing, activating previously inactive Mycobacterium. 14. What is the social factor that is letting the spread of malaria get out of control? A Climate change B Difficulty in producing a vaccine C Migration of people because of wars D An increase in drug resistant forms of malaria 15. Which of the following can prevent the spread of malaria? A Encourage the migration of people to the cities B Decrease carbon dioxide levels of the world C Increase the use of more antibiotics D Spray larvicide to stagnant water 16. Why there is a sudden increase in the number of case of TB in some countries? A Decrease in contact tracing B Increase in refugee camps C Water supply contaminated by sewage D Lack of aerosol insecticide 17. Which disease is not likely to be passed directly from parents to child? A cholera B malaria C sickle cell anaemia D tuberculosis 18. Cholera is no longer common in many countries. What is the reason for this? A Education of the citizens about the spread of the disease B Routine vaccination by local health authorities C Treatment of water supplies and separate sewage treatment D Treatment of water to control mosquitoes
CHAPTER 13 ffi Biology Term 2 STPM Chapter 13 Infectious Diseases 19. Which of the following increases the risk of contracting cholera? I drinking unpasteurised milk II eating shellfish which have fed on raw sewage III living in overcrowded conditions A II only C I and III B I and III D II and III 20. Which is the mosquito vector for malaria? A Culex sp. C Anopheles sp. B Aedes sp. D Mansonia sp. Structured questions 1. The diagram below shows the life cycle of malaria parasite. Stages of life cycle in human host Mitosis Cells taken up by mosquito when feeding on an infected human Male gametes Female gametes Zygote Reduction division (meiosis) Mitosis Infective stage enters human host when mosquito takes a blood meal (a) Describe how the malarial parasite is normally transmitted from an infected person to an uninfected person. [2] (b) Explain why malaria is restricted to the tropics. [2] (c) What are the effects on the body of the presence of malarial parasites in red blood cells? [3] (d) Explain why it has proved difficult to develop a vaccine for malaria. [3] 2. A patient was admitted with the following symptoms: t -PTTPGBQQFUJUF t 'FWFS t 4XFBUJOHBUOJHIU t 4IJWFSJOH t $IFTUQBJOXIFODPVHIJOHBOECSFBUIJOH t 'BUJHVF t Persistent coughing for more than three weeks (a) Suggest the most likely infectious disease contracted by the patient based on the symptoms. [1] (b) State the causative microorganism for the disease. [1] (c) Suggest the mode of transmission of the disease. [1] (d) Suggest two measures to control the spread of the disease. [2] (e) Suggest two reasons why the disease is on the rise in Malaysia even though it is believed that it has been eradicated. [2]
CHAPTER 13 ffi Biology Term 2 STPM Chapter 13 Infectious Diseases Revision Exercise 13 Objective Questions 1. D 2. D 3. B 4. D 5. A 6. B 7. A 8. A 9. D 10. D 11. C 12. D 13. B 14. C 15. D 16. B 17. B 18. C 19. A 20. C Structured Questions 1. B t ćF GFNBMFAnopheles mosquito sucks blood from an infected person t ćFQBSBTJUFTSFQSPEVDFJOTJEFUIFNPTRVJUP t ćFNPTRVJUPJOKFDUTTBMJWBXJUIQBSBTJUFJOUP uninfected person C t .BMBSJBJTUSBOTNJUUFECZAnopheles mosquito t ćF QBSBTJUF OFFET XBSN UFNQFSBUVSF UP complete life cycle in the mosquito t ćF NPTRVJUP SFRVJSFT BSFB PG TUJMM XBUFS UP complete cycle t .BMBSJBJT FSBEJDBUFEJOBSFBT PVUTJEF USPQJDT like North America (c) t ćFOVNCFSPGSFECMPPEDFMMTJTSFEVDFE t ćJTJTDBVTFECZCVSTUJOHDBVTFECZQBSBTJUFT t -FTT PYZHFO JT USBOTQPSUFE EVF UP MFTT haemoglobin t 5PYJOTBSFSFMFBTFEGSPNQBSBTJUF t 1SPEVDFTNBMBSJBTZNQUPNFHGFWFSGBUJHVF / headache /shivering E t Plasmodium has genetic complexity as it is eukaryotic t .BOZBOUJHFOTJONBOZTUBHFTPGMJGFIJTUPSZ t "OUJHFOTDIBOHFJOEJČFSFOUTUBHFT t .VUBUJPOTBSFFYQSFTTFEJOIBQMPJETUBHFT t *NNVOFTZTUFNBOUJCPEJFTDBOOPUBDUBHBJOTU stages within host cells 2. (a) Tuberculosis (b) Mycobacterium tuberculosis (c) Airborne (d) Regular screening for infection. Immediate isolation of infected patients. (e) The disease is spread by immigrants. No strict screening of the immigrants from TB endemic countries. Essay Questions 1. B J t *OGFDUJPVT EJTFBTF JT EJTFBTF DBVTFE by a type of pathogen such as virus, bacterium, protozoa, fungus, insect or arachnid. t *UJTUSBOTNJTTJCMFUIBUDBOCFQBTTFEGSPN an infected to a non-infected person t *OGFDUJPVT EJTFBTF DBO CF DPOUSPMMFE CZ breaking its transmission cycle such as eliminate the mosquito vector for dengue Essay questions 1. (a) (i) What is meant by infectious disease? [3] (ii) Describe the various ways of transmission of infectious diseases. [8] (b) Describe how social roles can lessen the spread of cholera. [4] 2. (a) Haemorrhagic dengue fever may develop in human after being bitten by an infected mosquito. Describe the course of its development. [9] (b) Describe the prevention and control of dengue. [6] ANSWERS
CHAPTER 13 ffi Biology Term 2 STPM Chapter 13 Infectious Diseases (ii) t 0OFXBZJTBJSCPSOFTVDIBTUVCFSDVMPTJT t 8IFO BO JOGFDUFE QBUJFOU DPVHIT bacteria in the aerosol formed can be breathed in and infected a healthy person t "OPUIFSXBZJTUISPVHIGPPEBOEESJOL such as cholera t %SJOLJOH XBUFS PS GPPE JODMVEJOH serving utensils when contaminated by cholera bacteria will pass the bacteria to uninfected person t %FOHVF GFWFS JT USBOTNJUUFE CZ Aedes female mosquito vectors t 8IFO B GFNBMF Aedes sucks the blood from infected patient the virus causing dengue is alive in its gut and when it feeds on an uninfected person, the virus is injected with saliva into the person t *OGFDUJPVT EJTFBTF DBO CF TFYVBMMZ transmitted from male to female or from female to male t "OFYBNQMFJT)*7XIJDIJTUSBOTNJUUFE in the seminal or vaginal fluid C t 0OFPGUIFTPDJBMSPMFTJTQVCMJDFEVDBUJPOPO what not to eat especially in time of outbreak even in developed countries t "OPUIFSSPMFJTUPQSPWJEFQJQFEJODIMPSJOBUFE water to avoid the use of contaminated water especially in cholera endemic areas t *OUJNFPGPVUCSFBL UIFTPDJBMSPMFJTUPQSPWJEF bottled filtered water especially to people in isolated rural areas with no piped in water t $MJOJDTBOE QVCMJDNVTU CF QSPNQU UP SFQPSU to the health ministry and authority in case of a cholera outbreak to prevent further deterioration 2. B t %FOHVF WJSVTFT BSF JOKFDUFE JOUP UIF CMPPE together in the saliva of infected mosquito. t ćF WJSVTFT BSF CSPVHIU UP FWFSZ QBSU PG UIF body in the bloodstream. t ćFZ CJOE BOE FOUFS XIJUF CMPPE DFMMT endothelial and fibroblast cells. t ćFZBMTPBUUBDLTUFNDFMMTJOUIFCPOFNBSSPX t ćJT DBVTFT UIF EZTGVODUJPO PG UIF CPOF marrow. t ćJT SFTVMUT JO UIF SFEVDUJPO PG UIF QMBUFMFU count. t ćFWJSVTFTBMTPBUUBDLQMBUFMFUTBOESFOEFSUIF platelets not functional. t ćJT SFTVMUTJOIBFNPSSIBHJDEFOHVFGFWFSBT any burst capillaries cannot be repaired. t ćFQMBUFMFUTBSFVTFEUPSFQBJSCVSTUDBQJMMBSJFT seen especially in the gum, tongue or skin of an infected person. t )BFNPSSIBHJDEFOHVFGFWFSXJMMMFBEUPEFBUI if an infected child has a fall causing unrepaired capillaries in the brain. (b) t %FOHVFDBOCFQSFWFOUFECZQSPUFDUJOHPOTFMG from Aedes mosquito bites. t ćJTDBOCFEPOFCZXFBSJOHDMPUIJOHDPWFSJOH the body, sleeping in mosquito free room or using insect repellent. t %FOHVF DBO CF DPOUSPMMFE CZ EJSFDUMZ destroying Aedes mosquitoes with chemical fogging. t "OPUIFS XBZ JT UP HFU SJE PG MBSWBM CSFFEJOH stagnant water. t -BSWJDJEF PS CJPMPHJDBM DPOUSPM PG NPTRVJUP larvae in stagnant water can control the spread of dengue. t 1VCMJDFEVDBUJPOJOJOGPSNJOH UIFQVCMJDOPU to create mosquito breeding containers with water is another form of control.
283 STPM Model Paper (964/2) Section A [15 marks] Bahagian A [15 markah] Answer all questions in this section. Jawab semua soalan dalam bahagian ini. 1. Which is true about the parts of the gas exchange system? Bahagian manakah adalah benar bagi sistem pertukaran gas? Part Bahagian Cartilage Rawan Cilia Silia Goblet cell Sel labu Smooth muscle Otot licin A Trachea Trakea Present Ada Present Ada Present Ada Absent Tiada B Alveolus Alveolus Absent Tiada Present Ada Absent Tiada Absent Tiada C Bronchiole Bronkiol Absent Tiada Present Ada Present Ada Absent Tiada D Bronchus Bronkus Present Ada Present Ada Present Ada Present Ada 2. Which feature of xylem vessels allows them to have reduced resistance to water movement? Yang manakah ciri salur xilem yang membenarkannya mempunyai rintangan pengaliran air yang kurang? A With companion cells supplying energy Dengan sel rakan bagi pembekalan tenaga B Lignin forms an incomplete secondary wall growth Lignin membentuk dinding sekunder tidak sempurna C There are no cross walls between vessel elements Dengan ketiadaan dinding melintang di antara unsur salur D Vessel elements join to form narrow tubes Unsur salur bergabung menjadi tiub sempit 3. Different substances, such as sucrose and amino acids, can move in different directions in the phloem sieve tubes. Which explanation is correct? Bahan seperti sukrosa dan asid amino dapat bergerak ke arah berlainan dalam tiub tapis floem. Keterangan yang manakah yang betul? A Both active transport and mass flow occur in each individual phloem sieve tube. Kedua-dua pengangkutan aktif dan pengaliran berkelompok berlaku dalam setiap tiub tapis floem individu B Active transport occurs in some phloem sieve tubes and mass flow occurs in other phloem sieve tubes. Pengangkutan aktif berlaku di dalam sesetengah tiub tapis floem dan pengaliran berkelompok di dalam tiub tapis floem yang lain. C Mass flow occurs in both directions at the same time in each individual phloem sieve tube. Pengaliran berkelompok berlaku di keduadua hala dalam setiap tiub tapis floem individu. D Mass flow occurs in different directions in different phloem sieve tubes at the same time. Pengaliran berkelompok berlaku di keduadua hala dalam tiub tapis floem yang berlainan pada masa yang sama.
284 Biology Term 2 STPM STPM Model Paper (964/2) 4. Which reactions take place in blood that is passing through active tissues? Manakah tindak balas yang berlaku dalam darah yang mengalir melalui tisu aktif? I HbO8 A Hb + 4O2 II HbO8 + H+ A HHb + 4O2 III HCO3 - + H+ A H2 CO3 IV H2 O + CO2 A H2 CO3 A I, II and IV I, II dan IV B I, III and IV I, III dan IV C I, II, III and IV I, II, III dan IV D II and III II dan III 5. Which event in the cardiac cycle that follows atrial systole is correct? Manakah kejadian dalam kitar kardiak selepas sistol atrium adalah betul? A A wave of excitation passes through the sinoatrial node, before spreading down to the base of the septum. Suatu ombak rangsangan mengalir melalui nodus sinoatrium sebelum menyebar ke pangkal septum. B Electrical impulses passes from the muscles of the atria to the muscles of the ventricles to cause ventricular systole. Impuls elektrik melalui otot atrium ke otot ventrikel untuk menghasilkan sistol ventrikel C Electrical impulses passes through conducting fibres, which cause a delay before spreading to Purkinje tissue. Impuls elektrik melalui gentian penghantaran yang melambatkan penyebaran sebelum ke tisu Purkinje. D The opening and closing of the semilunar valves occurs later than the opening and closing of the atrioventricular valves. Pembukaan dan penutupan injap semilunar berlaku lebih lambat daripada pembukaan dan penutupan injap atrioventrikel 6. Which of the following combination is correct for the roles of different structures? Antara yang berikut, manakah gabungan yang benar bagi peranan struktur yang berlainan? W – Release calcium ions after being depolarised. Membebaskan ion kalsium selepas dinyahkutubkan. X – Its binding head can pivot and bend causing the shortening of sarcomeres. Kepala pengikatannya boleh menegak dan melengkung seterusnya menyebabkan pengecutan sarkomer. Y – To enlarge the surface area of the post-synaptic membrane for depolarisation. Melebarkan luas permukaan membran pos sinaps untuk penyahkutuban. Z – Bind to troponin to expose the binding sites on actin filament. Terikat dengan troponin bagi mendedahkan tapak pengikatan yang terletak pada filamen aktin. T tubules Tubul T Endoplasmic reticulum Retikulum endoplasma Myofibrils Miofibril Calcium ions Ion kalsium A WY XZ B WY ZX C YW XZ D YW ZX 7. The action of hormone can be as follow: Tindakan hormon dapat berlaku seperti berikut: I It binds to receptor inside cytoplasm Hormon mengikat kepada reseptor dalam sitoplasma II It causes cascade effect Hormon menyebabkan kesan lata III It causes the synthesis of protein Hormon menyebab sintesis protein IV It activates the enzyme kinase Hormon mengaktifkan enzim kinase
285 Biology Term 2 STPM STPM Model Paper (964/2) Which are true of thyroxine? Yang manakah benar bagi tiroksina? A I and II C II and III I dan II II dan III B I and III D II and IV I dan III II dan IV 8. Which plant will flower if kept under a 24 hour cycle of light and darkness? Bunga manakah yang akan berbunga jika disimpan di tempat bercahaya dan gelap dalam kitar 24 jam? A Long day plant is kept in long dark period Tumbuhan panjang siang disimpan dalam kegelapan untuk tempoh yang lama B Short day plant is kept in short dark period Tumbuhan pendek siang disimpan dalam kegelapan untuk tempoh yang singkat C Long day plant is kept in long dark period but briefly exposed to far-red light Tumbuhan panjang siang disimpan dalam kegelapan untuk tempoh yang lama tetapi didedahkan seketika pada cahaya merah lampau D Short day plant is kept in short dark period but briefly exposed to far-red light Tumbuhan pendek siang disimpan dalam kegelapan untuk tempoh yang singkat tetapi didedahkan seketika pada cahaya merah lampau 9 Chorionic cavity is developed Pundi korion berkembang A before implantation stage sebelum peringkat penempelan B just after implantation stage sejerus selepas peringkat penempelan C after allantois is formed selepas allantois terbentuk D after foetus is formed selepas fetus terbentuk 10. Which hormone has the correct role? Hormon manakah menunjukkan fungsi yang betul? Hormone Hormon Role Fungsi Ecdysone Ekdison I Stimulate thoracic gland to produce ecdysone Merangsangkan kelenjar toraks untuk menghasilkan ekdison Neurosecretion Rembesan saraf II Stimulate the epidermis to produce hydrolase Merangsangkan epidermis untuk menghasilkan hidrolase Juvenile hormone Hormon juvana III Stimulate the production of nonpigmented epidermis Merangsangkan penghasilan epidermis tak berpigmen Ecdysone Ekdison Neurosecretion Rembesan saraf Juvenile hormone Hormon juvana A I II III B II III I C II I III D III I II 11. Which of the following statement is correct? Antara kenyataan berikut, yang manakah benar? A Gluconeogenesis is the formation of sugar Glukoneogenesis adalah penghasilan gula B Glycogenolysis is the formation of glycogen Glikogenolisis adalah penghasilan glikogen C Glycogenesis is the formation of glucose Glikogenesis adalah penghasilan glukosa D Glucosuria is the breakdown of glucose Glukosuria adalah penguraian glukosa
286 Biology Term 2 STPM STPM Model Paper (964/2) 12. Some halophytes and xerophytes have C4 cycle for carbon fixation because Sesetengah halofit dan xerofit mempunyai kitar C4 bagi pengikatan karbon untuk A to produce more water menghasilkan air yang lebih B to reduce water loss mengurangkan kehilangan air C to reduce sugar menurunkan gula D to oxidise sugar mengoksidakan gula 13. Which of the following statement(s) is(are) correct? Antara kenyataan berikut, yang manakah benar? I Antibody structure depends on peptide, hydrogen and disulfide bonds Struktur antibodi bergantung kepada ikatan peptida, hidrogen dan disulfida II Antibodies are proteins with both tertiary and quaternary structure Antibodi adalah protein yang mempunyai struktur tertier dan kuaterner III Antibodies have four polypeptides to provide four antigen binding sites Antibodi mempunyai empat polipeptida bagi memperuntukkan empat tapak pengikatan A I only I sahaja B III only III sahaja C I and II I dan II D II and III II dan III 14. What is(are) the function(s) of T-lymphocytes during an immune response? Apakah fungsi limfosit T semasa gerak balas imun? I destroy infected body cells menghapuskan sel badan yang terjangkit II differentiate into memory cells Membeza kepada sel memori III secrete antibodies merembeskan antibodi A I only I sahaja B III only III sahaja C I and II I dan II D II and III II dan III 15. What do the causative agents of HIV/AIDS, malaria and TB have in common? Apakah persamaan di antara agen penyebab HIV/AIDS, malaria dan TB? Cell membrane Membran sel Genes Gen Ribosomes Ribosom Respire Bernafas A Yes Ya Yes Ya Yes Ya Yes Ya B Yes Ya No Tak No Tak Yes Ya C No Tak Yes Ya No Tak Yes Ya D No Tak Yes Ya No Tak No Tak
287 Biology Term 2 STPM STPM Model Paper (964/2) Section B [15 marks] Bahagian B [15 markah] Answer all questions in this section. Jawab semua soalan dalam bahagian ini. 16. The graph below shows changes of human lung capacity. Rajah di bawah menunjukkan perubahan kapisiti peparu. 6 5 4 3 2 1 1.5 X Y Time / Masa Lung volume / dm3 Isi padu peparu / dm3 (a) What is represented by X? Apakah yang diwakili oleh X? [1 mark / 1 markah] (b) State two factors that can affect Y. Nyatakan dua faktor yang boleh mempengaruhi Y. [2 marks / 2 markah] (c) Determine/ Kenal pasti (i) the inspiratory reserve volume, isi padu pernafasan simpanan [2 marks / 2 markah] (ii) the residual volume isi padu baki [2 marks / 2 markah] 17. Sickle cell anaemia is one of inherited conditions linked to the structure and function of haemoglobin in which the transport and delivery of oxygen to tissues is less than normal. Anemia sel sabit adalah sesuatu keadaan diwarisi yang mempengaruhi struktur dan fungsi hemoglobin di mana pengangkutan dan pembekalan oksigen kepada tisu adalah tidak normal. Blood samples were taken from two people, L and M to investigate the ability of blood to carry oxygen. Sampel darah diambil daripada dua orang, L dan M untuk mengkaji keupayaan darah untuk mengangkut oksigen. t 1FSTPOL: without sickle cell anaemia Orang L: tiada anemia sel sabit. t 1FSTPOM: with sickle cell anaemia. Orang M: mempunyai anemia sel sabit.
288 Biology Term 2 STPM STPM Model Paper (964/2) The percentage saturation of haemoglobin with oxygen was determined over a range of partial pressures of oxygen and their oxygen haemoglobin dissociation curves are shown below. Peratus ketepuan hemoglobin dengan oksigen ditentukan pada pelbagai tekanan separa oksigen dan lengkung penceraian oksigen ditunjukkan di bawah. Partial pressure of oxygen / kPa Tekanan separa oksigen / kPa Percentage saturation of haemoglobin with oxygen Peratus ketepuan hemoglobin dengan oksigen 100 90 80 70 L M 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 (a) (i) State the partial pressure of oxygen at which haemoglobin is 50% saturated with oxygen for the two blood samples, L and M. Nyatakan tekanan separa oksigen ketika ketepuan oksigen adalah 50% bagi kedua-dua sampel darah, L dan M. L: M: [1 mark / 1 markah] (ii) From the two curves, describe how the dissociation curve for person M differs from the dissociation curve for person L. Daripada dua lengkung ini, huraikan bagaimana lengkung penceraian orang M berbeza daripada lengkung penceraian orang L. [3 marks / 3 markah] (b) Explain the advantage of the position of dissociation curve for people with sickle cell anaemia. Terangkan kelebihan kedudukan lengkung penceraian oksigen bagi orang yang mempunyai anemia sel sabit. [3 marks / 3 markah]
289 Biology Term 2 STPM STPM Model Paper (964/2) Section C [30 marks] Bahagian C [30 markah] Answer any two questions in this section. Jawab mana-mana dua soalan daripada bahagian ini. 18. (a) Describe the transport system in plants and state how it differs from that of animals. Huraikan sistem pengangkutan dalam tumbuhan dan nyatakan perbezaanya berbanding dengan sistem pengangkutan dalam haiwan. [8 marks / 8 markah] (b) Describe how the rate of heart beat is controlled. Huraikan bagaimana kadar denyutan jantung dikawal. [7 marks / 7 markah] 19. (a) Explain two applications each for synthetic auxin, synthetic gibberellin and synthetic ethylene. Terangkan dua aplikasi setiap satu bagi auksin, giberelin dan etilena buatan. [6 marks / 6 markah] (b) Explain the roles of anti-diuretic hormone (ADH) in human body. Terangkan peranan hormon anti-diuretik dalam badan manusia. [9 marks / 9 markah] 20. (a) Describe the structure and mode of functions of antibodies. Huraikan struktur dan cara fungsi antibodi. [8 marks / 8 markah] (b) Describe the stages in the immune response that lead production of antibody against a specific antigen. Huraikan peringkat dalam gerak balas keimunan yang menyebabkan penghasilan antibodi secara spesifik bagi sesuatu antigen. [7 marks / 7 markah]
290 Biology Term 2 STPM STPM Model Paper (964/2) Objective Questions 1. D 2. C 3. D 4. A 5. C 6. C 7. B 8. D 9. B 10. C 11. A 12. B 13. C 14. C 15. D Structured Questions 16. (a) Tidal volume (b) (i) Age (ii) Sex (c) (i) 6 dm3 – 3 dm3 = 3 dm3 (ii) 1.5 dm3 –0 = 1.5 dm3 17. (a) (i) L – 3.6 kPa M – 4.5 kPa JJ t 1FSTPOM’s curve is to the right (lower affinity) for oxygen with lower percentage saturation t "U IJHIFS PS MPXFS QBSUJBM QSFTTVSFT there is a smaller difference in percentage saturation with one another t "U QBSUJBM QSFTTVSF PG PYZHFO L1B PS 9.5 kPa, the difference in percentage saturation with one another is only 2% C t )BFNPHMPCJOJTMFTTTBUVSBUFEJOM than L at any partial pressure of oxygen t 4P BU QBSUJBM QSFTTVSFT JO UIF UJTTVFT XIFSF oxygen is unloaded from haemoglobin t )BFNPHMPCJOPGM dissociates more readily t ćJTJTUPDPNQFOTBUFGPSGFXFSSFECMPPEDFMMT (or less effective haemoglobin) in M 18. B t 5SBOTQPSUJOQMBOUTJOWPMWFTYZMFNBOEQIMPFN whereas that of animals involves arteries, veins and capillaries t 9ZMFNBOEQIMPFNIBWFEJČFSFOUNFDIBOJTNT for (mass) flow (or transpiration pull in xylem / pressure gradients in phloem) whereas animals requires heart t 9ZMFN IBT VOJEJSFDUJPOBM ĘPX XIFSFBT animals involves double circulation t 5SBOTQPSU JO QMBOUT JT OPU DMPTFE PQFO circulation (with pits/plasmodesmata) whereas animals has a closed circulation t *O QMBOUT XBUFS JT USBOTQPSUFE JO TFQBSBUF vessels from organic molecules / two (separate) systems whereas animals use same vessels/one (circulatory) system t *OQMBOUT MJWJOHBOEEFBEDFMMTBSFJOWPMWFEJO the transport system whereas in animals only living cells are involved t 3FTQJSBUPSZHBTFTBSFOPUUSBOTQPSUFEJOQMBOU system whereas animals’ system transports respiratory gases (oxygen/carbon dioxide) t 1IMPFNJO QMBOUT USBOTQPSUT TVDSPTFXIFSFBT animals’ system transports glucose t 3BUF PG ĘPX JO QMBOU USBOTQPSU TZTUFN JT slower whereas rate of flow is faster in animal transport system C t ćF IFBSU JT JOUSJOTJDBMMZ DPOUSPMMFE CZ UIF sino-atrial node (SAN/a specialised group of cardiac muscle fibres/pacemaker) t ćJTJTEVFUPUIFNZPHFOJDOBUVSFPGUIFIFBSU muscle/receives no impulse from outside to contract t 4"/ HJWFT PVU JUT PXO FYDJUBUJPO CFDPNF depolarised) and send it out to the atrial wall resulting in atria contraction t ćJTJTGPMMPXFECZFYDJUBUJPOHJWFOPVUGSPN atrio-ventrical node (AVN) which results in ventricular contraction t ćFFYUSJOTJD SBUFJTDPOUSPMMFECZBVUPOPNJD nervous system in response to environment t 8IFO FYFSDJTJOH UIF JODSFBTF JO SFUVSOJOH blood pressure is detected by receptors in the vena cavae t *NQVMTF JT TFOU UP UIF DBSEJBD BDDFMFSBUPSZ centre which has vagus nerve connected to SAN to increase the rate t "ęFS FYFSDJTJOH UIF SFDFQUPST JO BPSUJD PS carotid) body sends impulse to the cardiac inhibitory centre to SAN to decrease the rate t ćFIPSNPOFBESFOBMJOFXIFOSFMFBTFEEVSJOH exercising or when feeling excited can increase the rate by directly affecting the SAN t ćZSPYJO JT SFMFBTFE XIFO DPME UIBU DBO similarly affect the SAN to increase the rate 19. B t 4ZOUIFUJD BVYJO TVDI BT ϟOBQUIBMFOF BDFUJD acid (NAA) is used as rooting powder to stimulate root formation from stem cuttings dipped into the powder t "OPUIFS TZOUIFUJD BVYJO JT 4-dichlorophenoxytic acid (2,4-D) used as herbicide to kill dicotyledonous weeds t 4ZOUIFUJD HJCCFSFMMJO JT VTFE UP TQSBZ PO developing grapes so that the grapes formed are much larger t 4ZOUIFUJD HJCCFSFMMJO JT VTFE JO ĘPXFS induction especially plants like radish that normally do not flower ANSWERS
291 Biology Term 2 STPM STPM Model Paper (964/2) t 4ZOUIFUJD FUIZMFOF JO UIF BOBMPHVF GPSN JT used to produce fruits of uniform yellow colour in banana and mango after transported in the unripe condition t 4ZOUIFUJDFUIZMFOFJOMJRVJEGPSNJTQBJOUFEPO the rubber tree bark where tapping the bark will produce more latex C t "%) JT SFMFBTFE JOUP UIF CMPPE GSPN UIF posterior pituitary gland when receptors in the hypothalamus detected a decrease in blood water potential t "%)CJOETUPUIFSFDFQUPSTPGUIFNFNCSBOF of distal convoluted tubule and collecting duct in the kidney t ćF CJOEJOH DBVTFT B DBTDBEF PG SFBDUJPOT activating different kinases resulting vesicles with aquaporins move towards the membrane lining the lumen t ćFOUIFWFTJDMFTGVTFXJUIUIFNFNCSBOFBOE the vesicular membranes becomes part of the membrane increasing the aquaporins t ćF BRVBQPSJOT BMMPX GBTU EJČVTJPO PG XBUFS into the tubular cells and the water diffuses into the blood capillaries of the kidney t 4P "%) EFDSFBTFT UIF QSPEVDUJPO PG VSJOF and increases the water potential of the blood when the blood water potential decreases t "%)BMTPDBVTFTUIFUIJSTUGFFMJOHJOUIFUISPBU and only when we drink water that our blood water potential is increased to the normal level t 8IFO UIF CMPPE XBUFS QPUFOUJBM JODSFBTFT ADH detaches from the receptors and the aquaporins are withdrawn back into vesicles to be recycled t "%) JT OPU SFMFBTFE JOUP UIF CMPPE BT the receptors in the hypothalamus is not stimulated by high water potential 20. B t &BDIBOUJCPEZNPMFDVMFJTDPNQPTFE PGGPVS polypeptides, two long identical and two short identical ones t ćF GPVS QPMZQFQUJEF DIBJOT BSF CPOEFE by disulfide bonds at the hinge forming a Y-shaped structure in two dimension t &BDI NPMFDVMF IBT UXP JEFOUJDBM BOUJHFO binding sites at the two ‘arms’ t ćFGPVS DIBJOT BSF DPJMFE BOEGPMEFE JOUP B three dimensional globular shape t 0OFNPEFPGBOUJCPEZBDUJPOJTOFVUSBMJTBUJPO where antigen loses its attacking ability when bound t "OPUIFSNPEFJTBHHMVUJOBUJPOXIFSFBOUJHFOT like virus and bacteria are linked to form large aggregates when bound by many antibody molecules t "OUJCPEZ DBO DBSSZ PVU QSFDJQJUBUJPO XIFSF soluble antigen molecules are cross-linked by many antibody molecules into an insoluble mass t "OUJCPEZ DBO BMTP DBSSZ PVU DPNQMFNFOU fixation where the bound antigen resulting big pores in the plasma membrane of pathogenic cells or adhere to pathogens for easy engulfing by phagocytes C t "OUJHFO UIBUHFUTJOUP UIFCPEZJTSFDPHOJTFE as non-self (or foreign) t .BDSPQIBHFDBSSJFTPVUQIBHPDZUPTJTMFBEJOH to antigen presentation t ćFBOUJHFOQSFTFOUFEJTUIFOCJOEUPSFDFQUPS (or membrane) of B-lymphocyte(s) (or clonal selection of B-lymphocytes occurs) t )FMQFS 5MZNQIPDZUF BDUJWBUFT UIF #DFMMT (or T helper release interleukin/cytokines to stimulate B-cells) t ćF #DFMMT EJWJEF CZ NJUPTJT PS DMPOBM expansion of B-cells occurs) t ćFZNBUVSFUPGPSNQMBTNBDFMMT t ćFQMBTNBDFMMTQSPEVDFBOUJCPEZ
292 Agglutination Clumping of bacteria or viruses together to form a bigger aggregate Aldosterone Involves in homeostatic control of sodium ion in the blood Antibody Globular glycoprotein that acts against a particular antigen Antigen A protein in which the body recognizes as foreign or non-self B cells Lymphocytes that mature in the bone marrow and then spread throughout the body. Cardiac cycle Sequence of events which makes up one heartbeat which consists of one systole and one diastole Cerebral ischemia Oxygen deficiency in cerebrum Chemoreceptors Receptor cells that can be stimulated by chemicals Cholera Infection in the small intestine caused by the bacterium Vibrio cholera Deamination Conversion of an amino acid to a keto acid by the removal of the amine functional group Dengue An infectious disease transmitted by a vector, Aedes aegypti mosquito Diastole The event that occurs when the heart muscle relaxes. Double fertilisation A process in the flowering plant life cycle in which there are two fertilisations; one fertilisation results in the formation of zygote, whereas the second results in the formation of endosperm. Epitope A small specific part of a larger antigen, which is capable to bind with a specific antibody. Gluconeogenesis Synthesis of glucose from non-carbohydrate sources such as lactate, glycerol, fatty acids and some amino acids. Glycogenesis Formation of glycogen from glucose. This process is under the control of insulin. Glycogenolysis Breakdown of glycogen to glucose to provide immediate energy and to maintain blood glucose levels. Haemoglobin A respiratory pigment found in red blood cells to transport oxygen from lungs to the tissues Halophytes Plants that can live in soil with more than 0.5% of salt. Hepatomegaly Enlarged liver Incubation period A period of time between exposure and onset of symptoms