17 ACTIVITY: 1. Look at these three organisms below a. Are these plants or animals? b. How do you know this? c. Write down three visible characteristics that these organisms share. d. These organisms all belongs to the same group. Which group is this? e. How is organism B different to the other two organisms? 2. Choose the odd one out in each of the following groups of organisms by circling it and give a reason for your choice on the line provided (8pts) a. Bread mould, yeast, algae, mushroom ____________________________________ b. Leaf of life plant, spider plant, ginger, fern ________________________________ c. Frog, toad, newt, lizard ________________________________________________ d. Banana tree, sugar cane, black mangrove tree, pine tree ______________________ 3. Use the dichotomous keys to complete the activities below
18 4. A student saw these four marine organisms (A to D) on a scuba diving trip. Use the flow diagram below to correctly name the organisms. Write the name for each organism on the line below each. (4pts) _________________________ ____________________ ________________ ___________________
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20 Unit 3: Cytology Objectives: At the end of this unit, you will be able to: 1. Draw and label plant and animal cells 2. Differentiate between plant and animal cells 3. Recall the functions of the different parts of a cell 4. Construct a model of a cell using materials found around the home 5. Describe cell specialisation and site examples in plants and animals. 6. Describe diffusion, osmosis and active transport and site example of each in living systems. 7. Carry out investigations to investigate diffusion and osmosis
21 CYTOLOGY Organisms are made up of simple units called ‘cells’. The invention of powerful electron microscopes in the 1930s allowed scientists to learn much more about cells than they knew before. In this unit you will look at cells to learn more about how they function, how substances move in to and out of cells and how cells group together and perform specialized functions to form living organisms. The structure of cells The cell is the basic unit of living things. Some organisms, such as bacteria and protozoa, consist of one cell. We call these uni-cellular organisms. (You can see diagrams of these organisms in the figure below.) Most plant and animal species are multi-cellular. This means they consist of many cells that work as a system to keep them alive. Animal and Plant Cells Even though Animal and Plant cells are different they still have some parts that are common to both cells. The diagram below compares the two cells. Common parts: cell membrane – provides protection for the cell, allowing specific substances to pass in and out of the cell cytoplasm – holds the components of the cell, protect them from damage and gives the cell it’s shape nucleus – control and regulates the activities of the cell, carries genes (brain of the cell) vacuole – holds waste products of the cell and maintain water balance mitochondria – provides energy for the cell to carry out it’s functions other organelles – e.g. ribosomes – decodes messages, forms peptides bonds, endoplasmic reticulum – produces proteins, golgi apparatus – helps process and package proteins and lipids)
22 Animal cells Animal cells do not have rigid cell walls so they may not have a fixed shape. If vacuoles are present in the cell they are normally small. Plant cells Plant cells are normally larger than animal cells. They have a strong cell wall that encloses the cell and gives it a fixed shape. Plant cells usually have a large vacuole which is filled with cell sap (a solution of water and sugars). They also have organelles called chloroplasts. Chloroplasts are organelles that contain the chemical chlorophyll, which gives plants its green colour. The table below identifies the difference between plants and animal cell. Animal cells Plant cells No cell wall Have a cell wall No chloroplasts Many contain chloroplasts Not rigid, can change shape Rigid, have a fixed shape Often don't have vacuoles Have a central vacuole with cell sap When present, vacuoles are very small Vacuole is normally single and large Cell Specialization Different cells are specialized to carry out various tasks in living things and so cells can group together to work as a unit. Most cells cannot survive on their own, so they join together to function as multicellular organisms. Humans are multi-cellular organisms made up of billions of cells. In multicellular organisms, cells can become specialized to perform different functions in the body. These cells have different structures and functions, but they work together so that the organism can function as a whole. A group of similar cells form a tissue. For example, muscle cells form the tissue of your stomach wall and your heart. Different tissues together form an organ. The stomach is an organ and the heart is an organ. The organs work together in an organized system. For example, the stomach, together with other organs, forms the digestive system.
23 Example of Specialized Cells in animals (all specialized cells comes from the body’s raw materials known as stem cells.)
24 Plants also have specialized cells. The most common or important ones spoken about are the Xylem and Phloem cells in plants. Another example is the Root Hair Cells. Xylem – this transports water and other nutrients to the plants Phloem – this transports sugar (food) and other organic material to the plant Root Hair Cells – provides a bigger surface area for water to be taken in from the soil Example of Specialized cells in Plants Movement of substances through cells Cells need a supply of water and other substances that dissolve in water so that they can stay alive. Cells also need to get rid of waste produce. Dissolved substances move in to and out of cells across the cell membrane through three processes: 1. diffusion 2. Osmosis 3. Active Transport Diffusion Diffusion (the movement of particles from an area of high concentration to an area of low concentration) If you walk past the kitchen when someone is cooking you can usually smell the food from some distance away. This shows that smells spread through the air. Smells can also spread in water. Sharks, for example, can smell blood in the water from some distance away. We can smell food cooking and sharks can smell blood because of diffusion. The molecules or particles of gas and liquid move around at random. The natural tendency of these particles is to move from where they are highly concentrated (close together) to where they are less concentrated (more spread
25 out). The result is a movement of molecules of a substance along a concentration gradient from where the substance is highly concentrated to where it is in low concentration. This movement of particles through a gas (like air) or through a solution (when they are dissolved in liquid) is called diffusion. The diagram below gives a visual of what occurs during diffusion. Diffusion takes place in the cells of all living organisms (below are some examples of how diffusion occurs in living things) Where diffusion takes place Substance that is diffused How substances move Small intestine Glucose and amino acids from dissolved food From small intestine, through capillary walls into blood Lungs Oxygen (from the air) From the lungs through alveoli walls into the blood Lungs Carbon dioxide From the blood through the alveoli walls into the lungs for exhalation Pores of leaves Oxygen From the air spaces in the leaf, through the pores into the air (during photosynthesis) Pores of leaves Carbon dioxide From the air, through pores into the air spaces in the leaf Cell membrane of amoeba Amino acids, sugars and vitamins (products of digestion) From a food vacuole, through the membrane around it into the cytoplasm of the cell The table above shows how diffusion allows substances like oxygen and food to get in to our cells and waste products like carbon dioxide and other chemicals to get out of our cells. Diffusion is a passive process. It does not require added energy. Diffusion will continue until the molecules of the substance are evenly distributed through the gas or liquid.
26 Osmosis Osmosis (the movement of water molecules from an area of high concentration to an area of low concentration across a semi-permeable membrane) The most important function of the cell membrane is that it allows water and nutrients to pass in and out of cells. The cell membrane is partially permeable. This means that some substances can pass through it, but others can't. The membrane has small pores (openings) in it that allow the movement of substances. In general, substances pass through a membrane if their particles are smaller than the pores in the membrane. Water is one of the important substances that can move through cell membranes. When two solutions are separated by a partially permeable membrane, water passes through the membrane in both directions. The net flow of water is from the more diluted solution, which has a high concentration of water molecules, to the more concentrated solution, which has a lower concentration of water molecules. Water will continue to move through the membrane until the two concentrations are equal. The movement of water molecules from a more dilute solution to a more concentrated solution through a partially permeable membrane is called osmosis. You can think of osmosis as a special type of diffusion, in which only water molecules move from area to another. . Osmosis in plant cells Osmosis is the way that plants take up the water they need to stay alive. The cell membrane of the plant is a partially permeable membrane and allows the movement of water molecules into the cell. Turgidity Osmosis takes place across the cell membrane that separates solutions inside the cell from solutions outside the cell. The changes that happen inside plant cells as a result of osmosis cause visible changes in the plant. When plant cells are placed in a solution that is less concentrated than the solution inside them, water passes through the cell wall and cell membrane, through the cytoplasm and into the vacuole. The cell fills with water and become turgid. You can see this illustrated in Figure below. The diagram shows that water flows from the less concentrated solution outside the cell, through the cell wall and cell membrane into the cytoplasm and into the vacuole. The increased pressure in the vacuole is called turgor pressure and it causes the cytoplasm to press up against the cell wall. When the cell contains as much water as it can hold, it is said to be fully turgid. Turgid cells do not burst because the cell wall is strong enough to withstand the turgor pressure. Turgidity is important in plants because the turgid cells allow the plant to stay upright and gives it support. When cells lose water they become flaccid and the plant droops or wilts.
27 Osmosis in animal cells If animal cells are placed in a solution that is less concentrated than the solution inside them, water moves into the cells by osmosis and they swell up. If too much water flows into the cells they may burst because they have no cell walls. When animal cells are placed in a solution that is more concentrated than the solution inside them, water flows out of the cells as a result of osmosis. This causes the cells to shrivel up as seen in the figure. For animals is it very important to maintain an osmotic balance between cells and body fluids. Maintaining this balance is called osmoregulation. Active transport Sometimes substances move across the cell membrane and other cell membranes from a region where they are present in low concentration to a region where they are present in high concentration. That is, they move against a concentration gradient in the reverse direction to normal diffusion. Such movement is called active transport. It allows cells to build up stores of substances which otherwise would be spread out by diffusion. Active transport is an active process, which means that it requires energy, unlike diffusion which is a passive process and does not require energy. (This energy comes from respiration).
28 Worksheet. Answer the short question with the appropriate answer from the topic on cell biology 1. Label the diagram of the plant and animal cell below. (b) Use the Venn diagram below to compare plant and animal cells.
29 2. Fill in the blanks to describe the functions of the organelles below.
30 Link for worksheet on diffusion and osmosis https://www.liveworksheets.com/rp2847553fp
31 Match the specialized cells below to it function and how it is adapted for that function.
32 Unit 4 Autotrophic Nutrition Objectives: at the end of this unit, you will be able to: 1. Distinguish between autotrophic, heterotrophic and saprophytic nutrition 2. Describe photosynthesis and give a generalized equation for the process 3. Relate the structure of a leaf to its function in photosynthesis 4. Draw and label diagrams to show the external and internal structure of a leaf 5. Outline the main stages in photosynthesis and where they occur 6. Describe what happens to the products of photosynthesis 7. Test a leaf for starch 8. Describe investigations to show that light, chlorophyll and carbon dioxide are needed for photosynthesis. 9. Describe the effects of environmental factors on the rate of photosynthesis. 10. Discuss the importance of minerals for plant nutrition
33 Nutrition Nutrition means the process of providing or obtaining the food necessary for health and growth. We will be looking at nutrition in both plants and animals. Additionally, we will be looking at nutrients necessary for proper development and nourishment in humans. Nutrition can be placed in three (3) categories. - Autotropic nutrition - is a process in which the organism produces their food from the simple inorganic materials such as water, carbon dioxide and mineral salts in the presence of sunlight. All the green plants have an autotrophic mode of nutrition. e.g. - Heterotrophic Nutrition - Heterotrophic nutrition is a mode of nutrition in which organisms depend upon other organisms for food to survive. They can't make their food own like Green plants. Heterotrophic organisms have to take in all the organic substances they need to survive. Animals, including humans undergo heterotopic nutrition; this means we are heterotrophs because we depend on other organisms for survival. Feeding on other organisms gives us the various nutrients our body needs. - Saprophytic nutrition - In saprophytic nutrition the organisms obtain their food from dead and decaying organic matter of dead plants, dead animals and other decomposing organic matter. There are three major groups of saprophytes: These include bacteria, fungi and moulds. Photosynthesis Photosynthesis is the process by which plants make their own food. They use light energy from the sun and convert it to chemical energy or food.
34 Raw Materials needed for Photosynthesis There are four main raw materials needed for photosynthesis Carbon dioxide: come from the air, it diffuses into the leave through the stomata Sunlight: sunlight comes from the sun, it is trapped by chlorophyll Chlorophyll: chlorophyll is made in the leaf. Water: water comes from the soil, it get to the leaves through several processes namely osmosis, root pressure, capillarity and transpiration pull. Stages of Photosynthesis Photosynthesis takes place continuously in plants, but it is often describe in two stages. The light dependent stage or the light stage The light independent stage or the dark stage The light stage of photosynthesis During the light stage of photosynthesis, the chlorophyll is trapped by sunlight and is used to split water Molecules (H20) into Hydrogen (H2) and oxygen (O2). The hydrogen goes into the light independent Stage of photosynthesis and the oxygen diffuses out of the leaf. The light independent stage of photosynthesis During the light independent stage of photosynthesis, the hydrogen combines with carbon dioxide CO2 In a series of enzyme catalysed reactions to produce food in the form of glucose, C6H12O6. This process Requires some of the energy that was absorbed during the light stage but it does not require sunlight.
35 What happens to the products of photosynthesis? Most photosynthesis takes place in the leaves of plants. But all parts of the plant needs food, so the glucose has to be transported to other parts of the plant. Plants have special vessels called Phloem tubes that transport food around the plant. Glucose is also converted to starch and stored in different parts of the plant e.g. leaves, fruits, stems, and roots. The other product of photosynthesis is oxygen. Some of it is used by the plant for respiration and the rest diffuses out of the stomata of the leaves. Structure of the leaf.
36 Leaf adaptations for photosynthesis Photosynthesis occurs in the leaves of plants. The leaves are adapted to allow maximum photosynthesis. Some adaptations are listed below.
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38 Environmental Factors and the rates of photosynthesis. There are several factors that can affect the rate of photosynthesis. 1. Light: Notice in the graph that the rate of photosynthesis increases as the light intensity increases. Once a particular light intensity is reached, the rate of photosynthesis stays constant even if the light intensity increases. 2. Carbon dioxide: the rate of photosynthesis increases with an increase in carbon dioxide concentrations. The rate of photosynthesis reaches maximum level at a particular concentration of carbon dioxide. 3. Warmth: most plants row best in warm conditions. Note that rate of photosynthesis increases until optimum temperature is reached, after which rate of photosynthesis decrease as enzymes are denatured by very high temperatures. 4. Water: water is one of the raw materials needed for photosynthesis, but is is also an important factor in plant growth. Mineral Nutrition in Plants Like animals and humans, plants also need mineral nutrients in order to grow well. These nutrients are absorbed through their roots as solutions of salt from the soil. Plants need some minerals in large amounts, and some in small or trace amounts. These are called macronutrients and micronutrients. Some of the nutrients needed by plants are listed in the table below. Macro Nutrient like Nitrogen, Phosphorus and Potassium are needed in large amounts. Nitrogen is taken up in the form of nitrates and used to make plant proteins. Phosphorus is taken up in the form of phosphates and used to make cell membranes for the development of roots and for making nucleic acids. Potassium is taken up as potassium salts and used in photosynthesis. Magnesium is used in the formation of chlorophyll.
39 When a plant dies, and decomposes, these minerals are return back to the soil. However, if the plants are harvested as crops and fruits, the nutrients are removed from the soil. This can lead to deficiencies in the soil.
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41 6. After it is labelled, the diagram below will illustrate photosynthesis. Write each of the following terms on the correct numbered line. Then answer the questions that follow. Carbon Dioxide Glucose Oxygen Water 6. a. In photosynthesis, what substances come in from the outside? __________________ b. What substances are produced? ______________________ 7. What is the overall reaction (formula) for photosynthesis? _________________________________________ 8. Where does the energy for photosynthesis come from? __________________ 9. In what organelle of a plant cell does photosynthesis take place? _______________ 10. Explain why chlorophyll appears green to us in terms of what happens to different wavelengths of light that strike a chlorophyll molecule.
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43 Unit 5: Food and Nutrition Objectives: At the end of this unit, you will be able to: 1.List the six essential nutrients, their functions, sources and building blocks. 2.Carry out tests to identify different food substances 3. Describe and plan balanced meals 4. Identify and describe different types of eating disorders 5. Describe the properties of enzymes
44 Nutrition All organisms must be suplied with an energy source for metabolism. Plants are able to make their own food, but animals rely on other organisms for food. The energy obtained from food is used in general maintainance of the body, growth and repair. The foods that are consumed contain substances that assist the body to grow, and repair itself. These substance are known as Nutrients. Six Essential nutrients There are six essential nutrients that are found in the foods that we eat. Carbohydrates: Protein Fats/Lipids Vitamins Minerals Water. Carbohydrates: carbohydrates are the major energy source of the body. Foods that contain carbohydrates include rice, flour, sugar, pasta, ground foods, potato, cassava, bread, starchy roots and vegetables. The building blocks for carbohydrates is glucose. Fibre: it is important to note that fibre is also important in the diet of man. Fibre is found in whole meal and whole grain products, fruits and vegetables. Fibre helps the digestive system to work more efficiently, as it provide bulk to the faeces and allows it to move more easily through the digestive system. Eating a diet rich in fibre can assist in weight management and in preventing constipation. There are three major groups of carbohydrates, monsaccharides, disaccharides and polysaccharides. Monosaccharides are composed of one sugar unit, examples include glucose, fructose and galactose. They are also called simple sugars.
45 Disaccharides are composed of two sugar units joined together e.g. sucrose, maltose and lactose. They are referred to as complex sugars or non-reducing sugars. When two monsacchrides joint together to form a disaccharide , a condensation reaction occurs. Condenssation is a reaction in which two molecules join together and a water molecule is released. Disaccharides can be broken down into simple monsacchrides by hydrolysis, i.e. a reaction in which water is added. Polysaccharides are the third group of carbohyrates. These are made of long chains of sugar units bonded together and included starch, glycogen and cellulose. Starch is the name given to food stores in plants, glycogen is food stores in animals and cellulose is the fibre in the walls of plant cells. Protein Proteins are important in the body because they: - Are use to make enzyme, hormones, antibodies, DNA - Protein foods are also important for growth and repair of body tissues - They are used as a secondary source of energy. Protein foods include beans, peas, meats, eggs, milk… - Vegetarians need to ensure that they eat a variety of plant sources of protein to compensate for them not eating meat and meat products. - A deficiency of protein in the diet results in a disease called Kwashiorkor - The building blocks for protein are amino acids
46 Lipids/fats: Fats and lipids are very important in the body. They are used as a secondary source of energy, after carbohydrates have been used up. It is also important for storage, and function as insulation especially for animals living in cold regions. The building blocks for fats are fatty acids and glycerol. Food sources include butter, margarine, oils, nuts, avocados, meats. Fats can be saturated or unsaturated. Saturated fats come from animal sources, and are normally solids at room temperature, they contribute to the formation of bad choesterol and are bad for your health. Examples include fats found in meat sources like pork, beef, margarine, butter Unsaturated fats come from plant sources and are normally liquids at room temperature. They contribute to the formation of good cholesterol in the body. Examples include nuts, coconut oil, canola and olive oil, fish oils, avocado. Water Approximately 70% of your body is made up of water. As an essential nutrient water can be food in soups, water, teas, juices… water is important in the body to dissolve substances, namely vitamins B and C, and to form body fluids like saliva, sweat, urine, and blood. , it is also important in temperature regulation. Vitamins. Vitamins are micronutrients that are needed in the body in small amounts. There are two types of vitamins. Fat soluble vitamins (vitamins A,D,E,K) and water soluble vitamins (Vitamin B, C). They are needed in general for maintainance of the body and to maintain good health. They improve health by boosting the immune sysem and helps the body to function efficiently.
47 Minerals. Like vitamins, minerals are micronutrients needed by the body in small amounts. They help the body to function and give it strength. They are important to maintain health. Deficiency Diseases When the body does not get these essential nutrients in the correct proportion, it suffers from deficiency disease. Find outlined below some deficiency diseases and their causes.
48 Food groups In order to help us to eat healthy, food experts called nutritionists have grouped the foods that we eat into food groups. There are six food groups that are essential for health. Staples: rice, ground provision, pasta, flour Food from animals: pork, beef, fish, milk, eggs Legumes: peas, beans Fruits: mango, apples, guava, watermelon, cantelope Vegetables: callaloo, spinach, cabbage, broccoli Fats: oil, margarine The foods in the six food groups are eaten in different proportions to make a balanced meal or a balanced diet. Balanced meals. The diagram below shows the components of a balanced diet. Each block represents a particular food group and the size of the the block indicates the proportion of the diet which that food group should constitute. The recommended daily energy intake differs from person to person and is dependent on age, sex, and activity levels. Balanced meals are very important as it can help to prevent a variety of diseases like obesity and obesity related diseases like diabetes and hypertension. In the Caribbean, balanced meals are prepared by dividing the six food groups into different proportions and preparing meals based on those proportions of each food group. Staples: 41% Legumes: 21% Food from animals: 11 % Fruits: 11% Vgetables: 11% Fats and oils: 5% Note that the percentage of fats and oils is very small, those should be used sparingly along with sugars.
49 Energy requirements Note that energy requirements are generally greater for men, as they usually have more muscle, relatively less fat and weigh more than women. While in women, energy requirements are higher in the last three months of pregnancy and during breast feeding. Physical activity of an individual varies with both occupation and leisure. Some people are mostly sedentary (sitting for much of the time) and others are very active. Energy requirements for different levvels of activity can vary greatly. BMI Body Mass Index is a measure of body fat based on height and weight that applies to adult men and women. The formula is BMI = kg/m2 where kg is a person's weight in kilograms and m2 is their height in metres squared. A BMI of 25.0 or more is overweight, while the healthy range is 18.5 to 24.9.
50 Food Tests It is possible to carry out simple chemical tests to find out what substances are found in various foods. See table below for test for simple sugars, non-reducing sugars, starch, lipids and proteins. Benedict’s Test for reducing sugars - Clear blue to green to yellow to orange to brick red Non-reducing sugars test (does not change the colour of benedict’s solution which is blue/ remains blue) Biuret test for protein – pink to purple colour Test for Lipids/Emulsion/fats oils – cloudy white suspension Test for starch (iodine) – brown to blue black or purple
51 Eating Disorders Anorexia Nervosa: Anorexia nervosa: an psychological disorder characterized by an obsessive desire to lose weight by refusing to eat. In this disorder an individual may intentionally starve him/herself because they believe that they are fat. These individuals have abnormally low body weight and often with an intense fear of gaining weight and a distorted perception of weight. People with anorexia place a high value on controlling their weight and shape, and they often use extreme measures to prevent weight gain or to continue to loose weight. They often restrict the amount of food they eat, and may control their caloric intake by vomiting or taking laxatives, diet aids, or diuretics or by exercising excessively. Anorexia nervosa can be life threatning as individuals often equate their thinness with self worth as a result, it is classed as a mental disorder. Signs and Symptoms of Anorexia Nervosa: - Dieting despite being thin - Pretending to eat or lying about eating - Dramatic weight loss - Feeling fat despite being underweight - Harshly critical of appearance - Using diet pills, laxatives or diuretics - Throwing up after eating - Excessive exercising Treatment for Anorexia Nervosa: - Involves combination of psychological therapy and supervised weight gain. - Person needs to start treatment as early as possible to reduce the risk of serious complications of anorexia, particularly if they’ve already lost a lot of weight.
52 Bulemia Nervosa Bulemia nervosa, is another serious eating disorder. Bulemia Nervosa is an eating disorder characterized by binge eating followed by purging (frantic efforts to avoid gaining weight) People who suffer from bulemia secretly binge, that is, they eat large amounts of food with a loss of control over the eating, and later they purge, in an attempt to get rid of the extra calories in an unhealthy way. Oftentimes they may induce vomiting, misuse laxatives, or weight loss supplements, or use diuretecs after bingeing. Some may use other means to rid themselves of the extra calories like fasting, strict dieting or excessive exercise. Signs and Symptoms of Bulimia: - Frequent episodes of consuming very large amount of food followed by behaviors to prevent weight gain, such as self – induced vomiting - A feeling of being out of control during the binge-eating episodes - Self – esteem overly related to body image Treatment for Bulimia: - Antidepressants to reduce binge-purge cycles and relieve symptoms of depression - psychological counseling Obesity: obesity occurs when a person’s Body Mass Index become too high i.e above 30. These individuals are overweight and have extra fat that covers their bodies. This is extremely dangerous in that it increases the risk of diseases like hypertension, diabetes, high cholesterol…. .
53 Signs and Symptoms of Obesity: - Clothes feeling tight and needing a larger size - Having extra fat around the waist - Higher than normal body mass index and waist circumference - Anti – obesity medications - Lifestyle changes (healthy eating plan) - Exercise routinely Treatment for Obesity: - Anti – obesity medications - Lifestyle changes (healthy eating plan) - Exercise routinely Enzymes The chemical reactions occuring in cells are controlled by a group of proteins called enzymes. Enzymes are organic catalysts that speed up the rates of chemical reactions occuring in living cells. If it were not for these enzymes the chemical reactions occuring in our bodies would occur to slowly to sustain life. Enzymes are essential for building up and breaking down reactions in living systems. They can be used over and over agan and are not used up by the reactions, they are unchanged and free to catalyse more reactions, so only small amounts are needed in cells. Cells contain hundreds of different enzymes, each catlysing a different reactions. The molecule that an enzyme acts on is called its substrate. Each enzyme has asmall ara on its surface called the active site. The substrate attaches to the active site of the enzyme. The reaction then takes place and products are formed. When the
54 substrate joins up with the active site, it lowers the energy needed for the reaction to happen, allowing the products to be formed more easily. The substrate fits into the active site of the enzyme like a key fitting into a lock. This is sometimes called the ‘lock and key’ model of enzyme action. Note that after the reaction has been catlysed, the enzyme is free to act on more substrate molecules. Properties of enzymes Enzymes are all proteins Enzymes are specific for the type of reactions they will catalyse They are sensitve to toxins and poisons They are sensitive to pH: Different enzymes work in different pHs. The Ph inside cells is around 7 (neutral) and so most enzymes work best at this pH, however, in the digestive system, some enzymes found in the stomach, work best at an acidic Ph due to the presence of HCL in the stomach, others work best in an alkaline pH found in different parts of the digestive system. They are sensitive to temperature: they work best an an optimum temperature but are denatured by very high temperatures. Enzymes in the human body work best at about 370 C. This is shown in the graph below. As the enzyme is heated up to the optimum temperature, the increasing temperature speeds up the rate of reaction. This is because higher temperatures give the molecules of the enzyme and substrate more energy so they collide more often. More collisions mean that the reaction willt ake place more frequently. However, above the optimum temperature, the proteins that make up the enzymes are destroyed. We say that the enzyme is denatured.
55 The rate of most enzyme controlled reactions also depnd on the concentration of the substrate. The rate increases as the substrate concentration increase. As more substrate molecules collide with the active sites of oteh enzyme molecules. Eventually tho, the sustrate concentration become so high that all the active sites are working as quickly as possible. When this happens, only increasing the concentration of the nzyme will increase the rate. Naming Enzymes: There are thousands of different enzymes. Early scientists did not use a systematic way of naming enzymes and some of them are still known by their old names e.g. pepsin and catlase. Enzymes are now named after the substrate that they act upon. For example, maltase breaks digests maltose and sucrase works on sucrose. The enymes that are involved in digestion are classified into groups based on the type of food molecule that they break down. For example, carbohydrases work on carbohydrates, lipases work on lipids and protease works on proteins. SBA Activities: investigate the effects of temperature on the activity of amylase SBA Activity: to investigate the action of an enzyme, catalase
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57 Name: ______________________ Date: ___________ Nutrition Crossword
58 Name: _________________________ Class: ______ Date: ______________ Food Tests Instructions: Answer the questions concerning the different groups of nutrients and their reactions with the different chemicals. Color in any color changes expected in each test tube when mixed with the different substances.
59 Unit 6: Digestion Objectives: at the end of this unit, you will be able to: 1. Describe mechanical and chemical digestion 2. Describe the structure and function of the tooth 3. Differentiate among the different types of teeth 4. Describe how the digestive system works 5.Label the parts of the digestive system, and villi 6. Describe the absorption and assimilation of foods.
60 Digestion Food contains nutrients that our bodies need to survive. However, the food needs to be converted into a form that can be absorbed by the body. This is the function of digestion, to break down large complex food molecules into smaller, simpler substances. So nutrients like carbohydrates, proteins and lipids are broken down into their building blocks like glucose, amino acids, fatty acids and glycerol respectively. Food enters our digestive system through the mouth (ingestion). Before the food can be distributed and used in our bodies it has to be broken down or digested. There are two kinds of digestion: mechanical digestion and chemical digestion. Once food is digested, it is absorbed from the digestive system into the bloodstream. The blood transports the digested food throughout the body where it is assimilated and used in metabolic processes in the body. Food that is not digested or absorbed is passed out of the body, this is known as egestion. Mechanical digestion: is a purely physical process that does not change the chemical nature of the food. Instead, it makes the food smaller to increase both surface area and mobility. It includes mastication, or chewing, as well as tongue movements that help break food into smaller bits and mix food with saliva. Mechanical digestion also involves the muscles in the organs of the digestive system squeezing and pushing food through the digestive system and mixing it with gastric juices. Chemical digestion: Chemical digestion involves the secretions of enzymes throughout your digestive tract. These enzymes break the chemical bonds that hold food particles together. This allows food to be broken down into small, digestible parts. Teeth Function: The human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. Types: Humans have four types of teeth: incisors, canines, premolars, and molars, which each have a specific function. - Canines: used for griping and tearing (4 in number). These are very pronounced in carnivores. - Incisors: used for biting food ( 8 in number) - Pre-molars: used for chewing and grinding food (8 in number). These are more common in herbivores. - Molars: used for chewing and grinding foods. ( 12 in number) including the wisdom teeth.
61 Structure of the tooth: The structure of the tooth is divided into two main parts, the crown, which is the part that is located above the gum and the root, the part that is found below the gum. Enamel: Enamel is the hard calcified tissue on the surface of your teeth. It protects the dentin from acid and plaque. Because it has no living cells, enamel can’t protect itself from damage and needs good oral care to stay strong. – Dentin: Dentin is a sensitive layer of living tissue that communicates with the nerves in your teeth. If your teeth appear darker, it could be the dentin showing through the enamel. When dentin is exposed, your teeth may become very sensitive to heat and cold because these elements are directly contacting the nerves. – Cementum: Cementum is a hard connective tissue that covers tooth roots. It assists in supporting the tooth by anchoring the fibers of the periodontal ligament. Cementum helps prevent you from losing teeth prematurely. – Pulp: Pulp is the non-calcified tissue at the center of the tooth that contains nerves, connective tissue, and blood vessels. Your teeth receive nourishment from the pulp. Disorders of the teeth/gums Tooth decay - damage to a tooth's surface, which can lead to cavities. Abscess - a pocket of pus, caused by a tooth infection. Impacted tooth - a tooth did not erupt (break through the gum) when it should have. ... Misaligned teeth (malocclusion) Tooth injuries such as broken or chipped teeth. What are some of the things that we do to take care of our teeth?
62 Gingivitis: gum disease caused by plaque buildup The Digestive System The figure below shows the human digestive system. The tube extends from the mouth to the anus and is sometimes referred to as the alimentary canal. The digestive system is about 7-9 meters long, and food moves through the digestive tract in 1-3 days. The digestive system is divided into distinct regions that have special functions to perform. There are also associated glands like the salivary glands, pancreas and liver that produce special juices that are important in the digestive process. Movement of Food through the alimentary canal Food is first ingested and mixes with saliva from the salivary gland, and chewed by the teeth. The saliva softens the food and contains special enzymes, salivary amylase, which begins the breakdown of starch in food to maltose. The food is then passed from the mouth to the esophagus by the action of swallowing. The food is rolled into a ball called bolus and is pushed to the back of the throat by the tongue. Food enters the esophagus, the epiglottis, closes to prevent food from going down the trachea. The tubes of the gut have longitudinal and circular muscle cells int eh walls that are able to contract and relax alternately to force food along. These muscles are arranged such that the food can be churned. This wave like movement is called peristalsis. The stomach Food enters the stomach from the esophagus. There is a muscle called the pyloric sphincter at the other end of the stomach which helps to keep the food in the stomach until it is in a digested form. The food remains in the stomach for about 1-3 hours where it is churned with gastric juices. The stomach wall secretes gastric juices that contains HCl and the enzymes pepsin and renin. Proteins are broken down to long chains of amino acids called polypeptide chains by the enzyme pepsin. The HCL acid also stops the action of salivary amylase and makes an acidic environment for the enzyme pepsin to work. It will also destroy any harmful bacteria that may be in the stomach. The walls of the stomach are protected by a mucus lining. The rennin is important to clot the soluble protein casein and convert it to insoluble caseinogen in babies. The pyloric sphincter then relaxes and allows the liquid food (Chile) to enter the duodenum. Duodenum The duodenum is the first part of the small intestine. The small intestine can be as long as 8 metres in length. It is here in the duodenum that bile, pancreatic juice and intestinal juices are added to the food. Bile is made in the liver and stored in the gall bladder. It functions to emulsify or break up large clumps of fats to smaller fatty droplets. This allows it to be digested more easily by the enzyme lipase. Bile also contains sodium bicarbonate which neutralizes the acidic food coming from the stomach. And makes the food alkaline. The pancreatic juice secreted contains digestive enzymes and is also alkaline due to the presence of sodium bicarbonate. The pancreatic juice passes from the pancreatic duct into the duodenum. Pancreatic juice contains the enzymes, amylase, lipase and proteases like trypsin. The amylase completes the work started in the mouth and further breaks down starch to maltose, lipase breaks down fats to fatty acids and glycerol and proteases breaks up polypeptides into smaller dipeptides and peptides.
63 Intestinal glands in the walls of the small intestine then secrete intestinal juice which contains maltase, which converts maltose to glucose and peptidase which converts peptides into amino acids. Lipase also completes the digestion of fats to fatty acids and glycerol. Vitamins and minerals do not need to be broken down because they are already small enough for absorption. The food has now been completely broken down to their building blocks at this point and is now ready for absorption. ENZYME EXAMPLES DIGESTIVE ACTION SOURCE OF ENZYME WHERE IT ACTS Carbohydrase Amylase Maltase Lactase Sucrase Starch -------- maltose Starch -------- maltose Maltose--------glucose Lactose------- glucose Sucrose-------glucose Salivary gland Pancreas Walls of small intestine Mouth Small intestine Small intestine Proteases Pepsin Trypsin Peptidase Protein----- polypeptide Proteins----peptides Peptides----amino acids Stomach wall Pancreas Small intestine Stomach Small intestine Small intestine Lipases lipase Lipids------ glycerol and fatty acids pancreas Small intestine Absorption in Ileum The ileum is the second part of the small intestine. Some digestion is completed in the ileum, but the most important function is for absorption. The ileum is specially adapted for absorption as it contains many tiny finger-like projections called villi (villus singular). This increase the surface area to volume ratio for absorption. The villi also have even smaller projections called microvilli. In the ileum the glucose, amino acids, fatty acids and glycerol are absorbed into the blood stream via the villi. The villi are one cell thin which is small enough for the building blocks to diffuse into the blood vessels which form a dense network within the villus. These blood vessels are capillaries. The fatty acids and glycerol and some very small
64 undigested fat droplets, pass across the wall of the villi into lacteals. These lacteals are part of the lymphatic system. Blood and the lymphatic system are the two transport systems in the body. Assimilation The glucose, and amino acids travel in the blood plasma to the liver. The amino acids travel in the blood to cells in the body that build them up into new proteins. The buildup of materials into the protoplasm of cells is called assimilation. Amino acids are used for growth and repair, to make enzymes, hormones, antibodies, DNA. Any that is not used is de-animated by the liver. The nitrogen group is changed to urea, which his excreted by the kidneys in urine. The glucose is carried to cells where it is oxidized to release energy during respiration. Excess glucose is converted to glycogen in the liver and muscles, where it is stored. Some of the fatty acids and glycerol reforms into fats within the lacteals. All are carried in lymph within lymph vessels. These vessels transport fats to the neck where they pass into the blood the fats may be oxidized to release energy, or they may be stored in such places at the skin or around other body organs. The liver The liver is the largest glandular organ in the body. It has several important functions in the body. It is divded into the right and left lobes which are further subdivided. Blood from the intestines is passed to it by the hepatic portal vein. Some of the important functions of the liver include: - Fat metabolism: lipids are removed from the blood and broken down. Cholesterol is excreted in bile
65 - Storage of glycogen: excess glucose is converted to glycogen and stored in liver cells. Glucose is returned to the blood when it is needed - Deamination of amino acids: amino acids are broken down into ammonia and carbohydrate. The ammonia then combines with carbon dioxide to form urea. - Production of bile: bile is passed on to the gall bladder for storage - Destruction of red blood cells: old red blood cells are broken down in the liver - Production of plasma proteins: plasma proteins like albumins and fibrinogen that are used in blood clotting are produced by the liver - Storage of vitamins: vitamin A, D and B12 are needed for red blood cell formation in the red bone marrow - Destruction of toxins: harmful substances are chemically changed by the liver. E.g. alcohol and other drugs are broken down by the liver. - Elimination of hormones from the blood - Storage of heat: heat is made be the metabolic reactions in the liver and this is transferred to the large volume of blood sorted there. The large Intestine (colon) The small intestine joins the large intestine near the caecum and appendix. The large intestine is divided into three regions, the ascending, descending and transverse colon. The appendix is about the size of a little finger, it serves no known function in humans sometimes food may get stuck in the appendix and decomposes causing an inflammation of the appendix known as appendicitis. The appendix can then be removed from the body. The function of the colon is for the absorption of water and salts from the wastes. The leaves the undigested parts called feces that are stored for a short time.
66 Sometimes, the feces stays a little too long in the colon and too much water is absorbed from it, this leads to a condition called constipation. This can be prevented by eating a fiber rich diet, which helps the faeces to move along the colon more easily. Again, sometimes if the feces passes too quickly, it results in diarrhea. Undigested food materials including dietary fibre, make up the bulk of feces. Cellulose from plants is a large part of the faeces. Faeces are stored temporarily in the rectum and egested via the anus. Bile pigments and salts cause the brown color of faeces. Bacteria are also present in the feces so it is important to wash hands after defecating. Summary of digestive process.