PRE-U STPM BIOLOGY TERM 1

Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

synaptic knobs.
5. There are three types of neurones namely the motor, sensory and
associative neurones.
(a) Motor neurone
Motor neurone transmits impulse from the central nervous
system to the effector i.e. muscle or gland. Its structure is as
2 shown in Figure 2.47.
Dendron

Axon Nerve impulse Myelin sheath




Cell body Node of Ranvier Nucleus of Schwann Effector


Figure 2.47 Structure of a motor neurone
(b) Sensory neurone
Sensory neurone transmits impulse from the receptor to the
central nervous system.
Dendron Nerve impulse Cell body
Nucleus


Receptor cell Axon Myelin sheath Synaptic knob
Figure 2.48 Structure of a sensory neurone
(c) Interneurone (associative / intermediate neurone)
Interneurone receives impulse from the sensory neurone and
transmits it to the motor neurone. It is found in the brain or
spinal cord. Some can generate impulse and others transmit
impulse from one to the other. It varies in shape, bipolar and
multipolar with one or more dendrons or axons.





Axon Nucleus Dendron Dendrits




Axon
Cell body
Dendrons
Bipolar





Multi-polar
Figure 2.49 Types of interneuron


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6. Neuroglia are supporting cells closely associated with neurones. Exam Tips
They include the Schwann cell and the supporting cells in the Remember the general
brain and spinal cord. Schwann cell forms the myelin sheath that structure, including
insulates the axon or dendron which enables impulse to travel faster. drawings of motor, sensory
Other neuroglia supply nutrients to neurones, remove wastes from and associative neurones.
neurones, guide axon migration and provide immune functions.

Muscle tissue Summary 2
1. Muscle tissue is a group of cells or multinucleated syncytial tissue
Muscle tissue
which can contract. 1. Striated muscle
• Multinucleated fibres for
2. Muscles are divided into striated, cardiac and smooth muscles. movement in bones
(a) Striated muscle 2. Cardiac muscle
(i) Striated muscle also known as skeletal or voluntary muscle, • Branched fibres for
pumping in heart wall
consists of a bundle of muscle fibres attached to the bone 3. Smooth muscle
by tendons at both ends. Contraction of striated muscle • Non-striated fibres for
produces movement of the bone at the joints as well as movement in intestinal
wall
certain parts of the body.
Tendon Connective tissue One muscle fibre







Bone Complete muscle Bundle of muscle fibres
Figure 2.50 Striated muscle
(ii) Each fibre is supplied with a motor nerve through a special
neuro-muscular synapse called the end plate. Contraction
is a result of impulse sent to the muscle fibre. It is under our
conscious control. Each fibre consists of many myofibrils
as shown in Figure 2.51.

Nucleus




Sarcomere

Myofibril


A band I band



Figure 2.51 Part of a muscle fibre
(iii) Within each myofibril, there is an alternating dark and
light bands that produce striations seen under light
microscope. Dark band (A band) consists of thick myosin


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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

filaments supported at the centre by M membrane. Light
band (I band) consists of thin actin filaments supported
at the centre by Z membrane. The whole myofibril may be
considered as containing many units called sarcomeres as
shown in Figure 2.52.

Sarcomere Myosin filament Actin filament
2 (thick) (thin)










Z membrane A band I band M membrane H band
Figure 2.52
(b) Cardiac muscle
Cardiac muscle is only found in the heart. It is also striated,
consisting of fibres and myofibrils as in striated muscle but
differs in many ways.
(i) Cardiac muscle consists of individual cells and not syncytial
tissue.
(ii) Unlike striated muscles with straight fibres, cardiac muscle
fibre is branched and is connected to the neighbouring
fibres by bridges.
(iii) Each of the individual cells is separated from its adjacent
ones by intercalated discs so that excitation can be
transmitted effectively across them from cell to cell.
(iv) Cardiac fibre is not supplied with nerves from motor
neurone as it does not require impulses from the brain
before it can contract.
(v) The muscle is myogenic. It has its own pacemaker to
generate excitation that is transmitted across fibres before
they contract.
(vi) The structure of cardiac muscle is shown in Figure 2.53.

Cell surface
membrane
Nucleus


Intercalated disc





Cross bridge



Figure 2.53 Cardiac muscle
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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

(c) Smooth muscle
(i) Smooth muscle is also known as involuntary muscle, as it
is not under our conscious control but it is controlled by
the autonomic nervous system.
(ii) It is found in the alimentary canal, dermis, uterus, arteries
and trachea.
(iii) It is arranged in strands or layers. It is not branched or 2
attached to the bone.
(iv) It is made up of individual cells, each having its own
nucleus and plasma membrane.
(v) It has no striations, as its myofibrils do not align themselves
with thick and thin filaments forming bands.
(vi) It is supplied with nerves from the viseral motor neurone,
a part of the autonomic nervous system.
(vii) The muscle can contract rhythmically like peristalsis and
produces waves of contraction as in intestines. Its structure
is shown in Figure 2.54.


Nucleus
Cytoplasm
containing
actin and
myosin
filaments Cell surface
membrane

Figure 2.54 Smooth muscle
Connective Tissues
1. Connective tissues are groups of cells together with their products
that attach or are simply found between two different tissues.
They originate from the mesoderm layer of the embryo, becoming Language Check
Language Check
mesenchyme and later form the bones, cartilages, blood cells and
fibroblasts, which produce matrices. The matrices include the bone,
cartilage, fine fibres produced by fibroblasts. Blood cells produce
special proteins.
2. The compact bone has the following features:
(a) Bone is formed from osteocytes that secrete the matrix of
Language Check
calcium phosphate and carbonate, together with proteins. Language Check
(b) Compact bone consists of Haversian systems of cylindrical shape
with a Haversian canal in the centre. • Canaliculus – singular
Cannaliculi – plural

(c) The Haversian canal is supplied with blood vessels that bring • Lacuna – singular
raw materials for bone construction or it can be reversed as in Lacunae – plural
osteoporosis (a disorder of brittle bone).
(d) The Haversian canals are linked by a Volkmann’s canal, forming
an inter-connecting system for blood circulation.
(e) The osteocytes are found in small spaces called lacunae with
intricate tiny canaliculi for distributing the matrix during bone
formation.


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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

Summary (f) The bone structure is shown in Figures 2.55 and 2.56.

Haversian system
Connective tissues
1. Compact bone
• Produced by osteocytes
in lacunae of Harversian
system for body Lacuna with osteocyte
2 support and protection
in the bone.
2. Cartilage
• Produced by
chondrocytes in lacunae Volkmann’s canal
of protein fibres in
trachea for keeping it
hollow. Lamellae
3. Blood cells
(a) Red blood cells Blood vessels and nerves
• Biconcave filled with
haemoglobin for O Figure 2.55 Compact bone (cross section)
2
and CO transport
2
(b) White blood cells
(i) Granulocytes
• With many Haversian system
lysosomes for
phagocyting
antigens and old
cells
(ii) Agranulocytes
• Macrophages for
phagocytosis Rod-like Haversian
• B-lymphocytes systems
for producing
antibodies
• T-lymphocytes Bone marrow
cavity
for helping
B-lymphocytes




Figure 2.56 Compact bone (longitudinal section)

3. Cartilage has the following features:
(a) Cartilage is produced by chondrocytes which secrete the protein
matrix with no calcium carbonate.
(b) Cartilage differs from bone, as it is not as hard and it is flexible
but of high tensile strength.
(c) Chondrocytes are also found in lacunae but without canaliculus.
They receive oxygen and nutrients through diffusion.
(d) Cartilage is divided into three types: hyaline, elastic and fibrous,
depending on the types of protein in the matrices.
(e) One of the examples is the hyaline cartilage found in the rings of
trachea. The u-shaped rings prevent the trachea from collapsing,
and thus, allowing easy air passage.
(f) Matrix of the hyaline cartilage consists of glycoprotein and
collagen fibrils that make it translucent.



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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

(g) The structure of hyaline cartilage is shown in Figure 2.57.

Lacuna
Lacuna

Chondrocyte
Cartilage
2
Matrix
Lacuna
Cross section Longitudinal section
Figure 2.57 The structure of hyaline cartilage in trachea
4. Blood cells Exam Tips
Blood cells are divided into erythrocytes (red blood cells) and Remember the definition,
leucocytes (white blood cells). structures, functions
(a) Erythrocyte and distributions of
(i) Erythrocyte is formed in the bone marrow. The liver can six types of epithelia,
three types of neurones,
form erythrocytes in foetuses too. three types of muscles,
(ii) Before it matures, an erythrocyte which has a nucleus is compact bone, hyaline
later digested to enable more haemoglobin to be filled for cartilage, erythrocytes and
leucocytes.
the carrying of oxygen.
(iii) Its membrane is very thin, enabling easy gaseous exchange
i.e. oxygen and carbon dioxide to move in or out.
(iv) Its shape is biconcave so that its surface to volume ratio is
increased for gaseous exchange.
(v) The structure is shown in Figure 2.58.





2 μm

8 μm
Figure 2.58 Structure of erythrocyte
(b) Leucocytes
Leucocytes are divided into granulocytes and agranulocytes.
(i) Granulocytes
• Granulocytes have granules in their cytoplasm. The
granules are actually lysosomes. They are formed and
mature in the bone marrow.
• Granulocytes are divided into three types depending on
the pH of the dye that can stain them.
• The structure of the three types are shown below.






Neutrophill Eosinophil Basophill
Basophil
Neutrophil
Figure 2.59 Types of granulocytes
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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

(ii) Agranulocytes
• Agranulocytes do not have granules in their cytoplasm.
They are formed in the bone marrow and then get into
the blood stream.
• Agranulocytes are divided into monocytes and
lymphocytes.
2






Monocyte Lymphocyte
Figure 2.60 Types of agranulocytes
• Monocytes come out from the capillary into the
tissue fluid becoming bigger to form macrophages.
Macrophages engulf bacteria and dead tissue cells.
• Lymphocytes are divided into T lymphocytes, which
mature in the thymus gland and B lymphocytes, which
mature in the bone marrow. B lymphocytes produces
antibody and T lymphocytes help the B lymphocytes.


Quick Check 5

1. Plants seem to have lesser types of cells but more types of tissues than animals. Explain.
2. How are organs organised in plants and animals?





STPM PRACTICE 2


Objective Questions 3. A student examined a cell under a
microscope. He found that the cell has a cell
1. Why bacteria is determined as prokaryotes?
A It has a linear DNA wall. The cell does not contain membrane-
B The DNA has no ends bound organelles. What conclusion can be
C The DNA forms a complex with made by him from this observation?
histones A It is a bacterial cell
D The DNA is surrounded by specific B It is a plant cell
membrane C It is an animal cell
D It is either a plant or an animal cell
2. Which about a prokaryote is not correct?
A Its genetic material is in the nucleoid. 4. Prokaryotic cell can be differentiated from
B Its DNA combines with histone. eukaryotic cell whether
C It propagates via binary fission. A the cell has ribosomes or not
D It has 70S ribosomes. B the cell has a rigid cell wall or not




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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

C the cell carries out cellular metabolism 9. Which of the following is true of the part of
or not the chloroplast structure?
D the cell is compartmentalised by
internal membranes or not Content Function
5. Which of the following is the function of A Quantasome for storage of starch
lipoprotein in cell membrane? B Pigment for trapping light 2
A diffusion of water molecule and ions
B selective permeability on molecules and C Granule for converting
ions carbon dioxide to
C accumulation of monovalent ions carbohydrates
inside cell D Granum for carbon fixation
D protein synthesis

6. Which of the following statements are true 10. Which is the function of centrioles?
of plant membrane? A Holding together the sister chromatids
I There are forces of electrostatic of a chromosome
attraction between proteins and glycerol B Organising of the microtubules to form
in the lipid layer spindle fibres
II The membrane composes of C Helping in the pairing of homologous
hydrophillic and hydrophobic chromosomes
molecules D Breaking down of the nuclear
III The fatty acids are unsaturated ones membrane
IV It allows phagocytosis and pinocytosis
to occur 11. What is the function of the Golgi body?
V Transport of substances across it is by A It detoxifies poison.
B It synthesizes lipid
passive or active transport C It assembles ribosomes.
A I, II and III D It adds oligosaccharides to protein.
B III, IV and V
C I, II, IV and V 12. Which of the following can be abundantly
D I, II, III, IV and V found in a cell that primarily synthesises
lipids?
7. Which of the following organelle is only
found in animal cells? A Lysosomes
A Large vacuole C Microtubule B Ribosomes
B Centrosome D Mitochondrion C Rough endoplasmic reticulum
D Smooth endoplasmic reticulum
8. Which of the following statements about
chloroplast are not true? 13. Human hair contains keratin that composes
I It is not found in prokaryotic cell of high amino acid cysteine. Which bond is
II It contains DNA responsible for straightening or curling hair
if treated?
III It is covered by a layer of membrane A Hydrophobic interaction
IV It has crista extensions B Disulphide bridge
A I and II C Hydrogen bond
B I and III D Ionic bond
C II and III
D III and IV


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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

14. Which combination is of true of cells with 18. Which of the following is true in xylem wall
extensively developed? thickening?
I Liver P With ring-like structure
II Pancreas Q With spring-like structure
III Salivary gland R With step-like structure
IV Adrenal cortex S With net-like structure
2 A I and II T With abundant holes
B I and IV
C II and III P Q R S T
D III and IV A Reticulate Annular Helical Pitted Scalariform
B Helical Annular Pitted Reticulate Scalariform
15. Which combination is correct? C Annular Helical Scalariform Reticulate Pitted
Structure Function D Pitted Reticulate Helical Scalariform Annular

A Microtubule Movement of 19. Which of the following contains lignin
organelle and is stained red when treated with acidic

B Nucleus Translation of phloroglucinol?
mRNA I Collenchyma
II Schlerenchyma
C Rough Modification of
endoplasmic lipid III Sieve cell
reticulum IV Tracheid
A II and III
D Smooth Synthesis of B II and IV
endoplasmic protein C III and IV
reticulum D I, III and IV


16. Which of the following cells has not 20. A pear has a hard texture but juicy. Which
undergone specialisation? cells give the characteristics?
A Sieve tube A Collenchyma and fibres
B Endodermis B Fibres and sclereids
C Tracheid C Parenchyma and collenchyma
D Meristem D Parenchyma and sclereids

17. Which of the following statements about a
sclerenchyma cell is true? 21. What epithelium lines the intestinal
A The mature cell exists in the region of innermost layer?
the plant that has stopped growing in A Stratified squamous
length. B Simple squamous
B The cell can retain the ability to divide C Columnar
and differentiate into other types of D Cuboidal
plant cells.
C The cell can perform most of the 22. The transitional epithelium found in the
metabolic functions, synthesise and mammalian urinogenital system is for
store various organic products. A secretion of mucus
D The mature cell has primary wall that is B glomerular filtration
relatively thin and flexible, and most of C reabsorption of water
the cells lack secondary cell wall. D elasticity for urinary bladder


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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

23. Which of the following is correct? 27. Which protein subunits are true of the
cytoskeleton fibres?
Cardiac Smooth Striated
muscle muscle muscle Microtubules Microfilaments Intermediate
filaments
A Myogenic Syncitial Autonomic
control A Fibrous Tubulin Actin
dimer 2
B Syncitial Myogenic Autonomic B Tubulin Fibrous Actin
control
dimer
C Autonomic Syncitial Myogenic C Tubulin Actin Fibrous
control dimer
D Myogenic Autonomic Syncitial D Fibrous Actin Tubulin
control dimer


24. Which of the following characteristics is not 28. Which is not true of parenchyma cells?
that of hyaline cartilage or compact bone? A Most parenchyma cells are
A To withstand compression undifferentiated and meristematic.
B To bind with connective tissues B Photosynthesis occurs within the
C Their cells are chondroblas and chloroplast of parenchyma cells of the
osteoblas respectively leaf.
D Their cells produce matrix substances C Parenchyma cells have thicker primary
walls than those of collenchyma cells.
25. What is meant by resolution in microscopes? D Most fleshy fruit tissue is composed
A The product of the magnifications of mainly of parenchyma.
the eyepiece and the objective lenses
B The shortest distance between two 29. Which tissue function is correct?
objects that can be seen separately
C The size of the smallest object that can Tissue Function
be seen A Connective Lining of the body cavity
D Twice the wavelength of the light used
to illuminate the specimen
B Epithelia Movement
26. Which of the following statements is the
advantage of using transmission electron C Muscle Protection and support
microscope to study cell organelles?
A It can be used to examine three- D Nerve Communication
dimentional structures of the organelles.
B It requires a relatively simple preparation
of the specimen.
C It does not require a special technical
skill to operate.
D It has high resolution.









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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

Structured Questions
1. The diagrams show interaction among endomembrane system in an animal cell.





W
2




X
Z

Y






(a) Name the structures labelled W, X and Y. [3]
(b) Name and state the importance of process Z. [2]
(c) How does the membrane of X differ from the membrane of Y. [1]
(d) What would happen if there is an excessive leakage due to a large number of structure Q in a
cell? [1]


2. Three different types of plant cells X, Y and Z are shown in the diagram below.













X Y Z

(a) Name cell X, Y and Z. [3]
(b) State one characteristic of cell Z. [1]
(c) (i) Differentiate between cell X and cell Y. [2]
(ii) What is the difference between the mechanical support of cell X and cell Y?[1]





Essay Questions
1. Explain the structures and functions of the following:
(a) cell wall,
(b) cytoplasm. [15]



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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

2. (a) Distinguish the chromosome of a bacterium with that of a eukaryote. [4]
(b) Describe the structure and functions of the Golgi apparatus with the help of a labelled
diagram. [11]
3. (a) Two ultra-structures of xylem are important in transport and mechanical support.
Explain. [6]
(b) Describe the distribution and functions of three types of simple epithelia. [9]
4. Explain the meaning of meristem. Describe the structure, locations and functions of different
types of meristem with reference to suitable examples. [15]













ANSWERS



1 (e) Both have ribosomes. They are required to
produce proteins especially enzymes to control
1. They are simpler and smaller cells. They contain fewer cellular reactions.
genes, unable to carry out complicated processes at the
same time. They contain fewer organelles, not capable 3
of carrying out reactions in compartments with little
or no interference. They have no enveloped organelle 1. Both contain DNA with genes and ribosomes, capable
like nucleus, mitochondria and chloroplast where of independent survival like bacteria. They can divide
specialised processes occur with high efficiency. Their like bacteria. Mitochondria require pyruvic and other
cell wall is less rigid to support greater load. organic acids, ADP, phosphate, NADH to produce
ATP required by the cell. Chloroplasts require carbon
2. They can be both autotrophs and heterotrophs. dioxide and mineral ions to produce glucose and fatty
Autotrophs can be photoautotrophs which are capable acids for the cells.
of photosynthesis, and chemoautotrophs which are
capable of chemosynthesis. Heterotrophs can be 2. Nucleus contains DNA that codes for the production
saprophytes which feed on ‘dead’ organic substances, of enzymes. It is the place where RNA and ribosomes
or parasites that feed on ‘living’ organic substances. are also produced. The mRNA from the nucleus
is translated by the ribosomes on the rough ER to
become proteins inside its cisternae. From here the
2 proteins will be sent to the Golgi apparatus where they
are packed in the form of vesicles for export out of the
1. (a) Both have cytoplasm. It is the cell body where all cell. However, if the proteins exported are hydrolases,
reactions of the cells occur. they are required to be packed like lysosome so the
(b) Both have nucleus. It contains DNA and genes, hydrolases will not digest the membrane packing them.
which are required to control all cellular activities
through the productions of proteins. 4
(c) Both have plasma membrane. It is the structure
15
that controls the exchange of substances between 1. Radioactive DNA contains N instead of the normal
the cell and the environment. 14 N. As a result, the radioactive DNA is heavier than
(d) Both have mitochondria. They are the power the normal DNA. Such minor weight difference can be
generators of the cell where they produce ATP as separated by ultra-centrifuge, which revolves 100,000
energy source for cellular activities. times gravitational force.




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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles
2. There is a phase change in the light that passed through (b) Thin cell wall
different refractive indices. Such phase difference can (c) (i) Cell X is non-living whereas cell Y is living.
be neutralised or darkened by using suitable phase
plate i.e. clear plastic of certain thickness and shape. Cell X with wall thicken evenly while cell Y
with wall thickened at corners.
3. Electron beam has a wavelength shorter than 10 nm. (ii) Cell X provides mechanical support with
The limit of resolution of a microscope is about half
the wavelength of the radiation used to view the lignified wall while cell Z provides support
with non-lignified wall.
2 specimen. Two points shorter than 200 nm is beyond
the resolution of the light microscope and therefore Essay Questions
electron microscope is required to resolve them.
1. (a) • There are two types of cell wall, the primary
cell wall and the secondary cell wall.
5
• The primary cell wall is a thin layer, found on
1. Plants have six major types of tissues i.e. meristem, the outer layer of the secondary cell wall.
parenchyma, collenchyma, sclerenchyma, xylem and • It consists of randomly arranged microfibrils of
phloem. Xylem is a complex tissue made up mainly of cellulose in an amorphous matrix as shown
tracheid and vessel, so is phloem, made up of mainly below.
sieve tubes and companion cells. Animals have four
major types of tissues i.e. epithelial, muscular, nervous
and connective tissues. Each of these four types is
divided into many subtypes.
2. Plant organs consist of root, stem, leaf, flower and fruit.
Each is organised from meristem like apical meristems
that form the root and shoot. Special primordial Microfibril
outgrowths will organise to form more roots, branches, Matrix
leaves, flowers and fruits. Animals have their organs
formed during embryonic development and no new
organ is formed thereafter. • The primary cell wall is porous. It enables water
to be transported apoplastically along it.
STPM Practice 2 • The secondary wall is made up of regularly
arranged microfibrils or bigger macrofibrils.
Objective Questions • The fibrils are arranged in layers of parallel
rows, which are perpendicular to the upper
1. C 2. B 3. A 4. D 5. B
or the lower layers as shown below.
6. C 7. B 8. D 9. B 10. B
11. D 12. D 13. B 14. B 15. A
Macrofibrils
16. D 17. A 18. C 19. B 20. D
21. D 22. D 23. D 24. A 25. B
26. D 27. C 28. C 29. D

Structured Questions • The matrix in the secondary wall is impregnated
1. (a) W : Golgi apparatus with lignin, forming a hard and impervious
X : Lysosome layer.
Y : Phagosome • The cell wall protects the cell from physical
(b) (i) Autophagy injuries and haemolysis.
(ii) To break down worn out organelle • It supports the plant through cell turgidity or
(c) The types of protein associated with the mechanical strength for tall woody trees.
membrane. • It controls growth, limiting individual cell size
(d) Autolysis in which the whole cell will be broken and the shape of the cell through orientation of
down. the fibrils in the wall.
2. (a) X: Sclerenchyma • It forms a system of transport pathways
Y: Collenchyma for water and mineral ions. Water can both
be transported along the porous cell wall in
Z: Parenchyma


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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles
apoblast or through the plasmodesmata of the • The Golgi apparatus (GA) is made up of a stack
symplast pathway. of at least three flattened sacs called cisternae.
(b) • Cytoplasm is aqueous in nature, consisting of • The cisternae are kept in place by microfilaments
the ground substance and cell inclusions. with a thin layer of cytoplasm between one
• The ground substance or cytosol is the soluble cisterna to another.
part of the cytoplasm. It contains gases, mineral • Each cisterna is covered with a layer of
ions and organic substances. lipoprotein menbrane with a colloidal sol
• The cell inclusions include the fine fibrils i.e. in it. 2
microtubules and microfilaments. • The colloidal sol within has enzymes and
• The microtubules are fine unbranched tubules proteins like glycoprotein that are derived from
with diameter of 25 nm, a wall of 5 nm thick the endoplasmic reticulum.
and vary in length. • Besides protein, other substances such as lipids
• The microfilaments are fine filaments made of like steroid hormomes and carbohydrates such
protein with a diameter of 7 nm and a length of as cellulose may be found within the cisterna.
several μm. • Each cisterna is formed with vesicles that keep
• The cytoplasm stores vital chemicals including pinching off from the endoplasmic reticulum at
fats. one side i.e. the cis side.
• It is the site for certain metabolic pathways • On the other side, i.e. the trans side, vesicles
such as glycolysis, synthesis of fatty acids and keep pinching off from the periphery of the
amino acids. cisterna.
• It enables organelles to move about in it. These • Therefore, the outer trans cisterna will finally
organelles include mitochondria, chloroplasts, disappear completely to become vesicles.
ribosomes, lysosomes and vacuoles. • The main function of the GA is to package
• It forms the cytoskeleton that determines the secretion in the form of vesicles.
shape of the cell. • Thus, the GA packages proteins, especially
enzymes, for internal transport or use within
2. (a) • The chromosome of a bacterium lies freely the cell.
in the cytoplasm of the cell whereas that of • The GA can form larger vesicles in the form of
eukaryote is found in the nucleus. lysosomes with hydrolases.
• The chromosome of a bacterium consists of one • The GA also packages secretions like digestive
circular DNA whereas the eukaryote consists of juice from digestive glandular cells of the
linear DNA. stomach, pancreas and small intestine.
• The chromosome of the bacterium is naked, • The GA also packages hormones, both steroid
not bound to histone protein, but the eukaryote and peptide from cells of the endocrine glands
has histone bound to it. e.g. Leydig cells.
• The chromosome of a bacterium has no 3. (a) • One ultra-structure of mature xylem cells is no
centromere and chromatids whereas the protoplasm but hollow lumen.
eukaryote has two chromatids attached at the • The mature vessels join end to end without
centromere during cell division.
• The chromosome of a bacterium has no cross walls to form long continuous vessels.
more than 3500 genes whereas the larger • These hollow vessels offer no resistance to
water flow from the roots into the leaves.
chromosome of eukaryote has more than that • Another ultra-structure of the mature xylem
number.
cells is their thick lignified hard wall enabling
(b) them to support the plant.
Vesicle budding • These thick-walled vessels enable water to
off and moving be transported upwards by high suction and
towards cell
would not collapse.
Cisterna
• Such thick hard wall is made up of layers of
Network of Inter–cisternal cellulose fibres impregnated with lignin.
tubules space (b) • Simple squamous epithelia are found in alveoli
of lungs, endothelium of blood vessels and
Bowman capsule of kidneys.
Sac from ER
added to the • In the alveoli, the thin epithelia enable oxygen
convex face to diffuse into the blood capillaries and carbon
dioxide to diffuse out.




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Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles
• Through the endothelium, oxygen and nutrients • The cell wall is thin, made up of only primary cell
can diffuse out of the blood capillaries while wall.
carbon dioxide and urea can diffuse into them. • The nucleus is large, relative to the volume of the
• Simple cuboidal epithelia are found in the cell.
tubules of the nephron of kidneys. • There is no intercellular space; the cells are compact.
• In the proximal convoluted tubule, their plasma • The protoplasm is dense, with few organelles and
membrane facing the lumen is modified to the organelles are small.
form ultra-villi for reabsorption of molecules. • Apical meristem is found at the shoot and root tips.
2 • In the distal and collecting ducts, the epithelia • Its function is to produce primary tissues, such
form tubule to channel urine though can be as tissues found in a herbaceous plant.
affected by ADH for special water reabsorption. • Vascular cambium is found mainly in woody stems
• Simple columnar epithelia are found in the and roots.
outermost lining of the stomach and intestines. • Its function is to produce secondary xylem (wood)
• These epithelia serve more of protection as and phloem.
their outer surfaces are covered with mucus. • Cork cambium (phellogen) is found on the outer
• In the small intestine, their plasma membranes layer of dicotyledonous woody stems and roots.
have special transport proteins for absorption • Its function is to produce cork cells (phellem) on
of digested food molecules. the outside and secondary cortex (phelloderm) on
4. • Meristem is a group of cells that are able to divide the inside.
and continue to divide. • Intercalary cambium is only found in
• It consists of a group of initial cells that can divide monocotyledons especially Gramineae.
very fast. The cell products will divide at a slower pace. • It is a thin layer of cells above the node of the stem
• After cell division, one of the daughter cells will when it is young. Its function is to produce more
move away and become differentiated while the cells for the internode and will later disappear.
others are retained and continue to divide.
• Therefore, meristem is a localised tissue and tends
to move up for the bottom cells to grow as in the
shoot apical meristem.
• All the cells in the meristem are young and have not
undergone differentiation.
• The cells have isodiametric prismatic shapes.




































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