Cell Biology Summary Notes with Somaliland Form 4 Biology Past Exam Practices and Answer Key by Ahmed Omaar

Form 4 Biology
Chapter 7 – Cell Biology – Cell Structure and Function
Summary Note with Exam Practice and Answer Key
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Form 4 Biology
Cell structures Description Function
Cell wall
(Cellulose cell wall)
(Cell wall is non living)
 It is the outer tough
and rigid layer of
the plant cell.
 Cell wall is made
up of cellulose.
 Animal cells have
no cell wall.
 Protection
 Support
 Gives shape to the plant
cell..
Plasma membrane
(Plasma membrane)
 It is a double layer
or phospholipids
embedded in a
variety of proteins.
 It acts as a
selective barrier
between the cell
and its surrounding
 It isolates the contents of
the cell from its external
environment.
 It regulates movement of
substances in and out of
the cell.
 It allows interaction with
other cells.
Cytoplasm
 Jelly like substance
that contains
organelles.
 The liquid portion
of the cytoplasm is
called cytosol.
Site of most chemical
reactions in the cell.
Nucleus
(contains most of the cellular
DNA)
(Control center of the cell)
 It is a round double
membrane bounded
organelle which
contains most of
the genetic material
in the cell.
 It controls the activities of
the cell.
 It controls cell
reproduction (it controls
cell division)
 It stores the cell’s genetic
material.
Nuclear membrane (nuclear
envelope)
 It is a double
membrane which
surrounds the
nucleus of
eukaryotic cells.
 The nuclear
membrane contains
small holes called
nuclear pores.
 It protects the nucleus.
 It separates the materials
in the nucleus from rest of
the cell’s contents.

Form 4 Biology
Nuclear pores  Nuclear pores are
small holes on the
nuclear membrane.
 It allows materials to pass
between the nucleus and
cytoplasm.
Nucleolus  Small dark
structure in the
nucleus
 Synthesizes ribosomes
(site of ribosome
assembly)
Chromatin
(Heredity material)
 Thin thread-like
structure, made up
of DNA and
proteins.
 During cell
division,
chromatin
condenses into
chromosomes.
 Provides instructions for
the cell activities.
Ribosomes
(Rounded organelles found in
cytoplasm or attached on
Rough ER)
 Ribosomes are
made up of RNA
and proteins.
 Ribosomes are not
surrounded by a
membrane.
 Ribosomes are
found in both
prokaryotic and
eukaryotic cells.
 Site where proteins are
made (Synthesis proteins).
Rough Endoplasmic
Reticulum
(Rough ER)
 A network of
parallel
interconnected
membranous tubes.
 Ribosomes attach
on the surface of
Rough ER.
 Transports proteins made
by the ribosomes.
Smooth Endoplasmic
Reticulum
(Smooth ER)
 A network of
parallel
interconnected
membranous tubes.
 Has no ribosome
on its surface.
 Synthesis
lipids

Form 4 Biology
Golgi apparatus
(Golgi body or Golgi
complex)
 Golgi bodies are
membrane-
bounded sacs
found in most
eukaryotic cells.
 Golgi body was
discovered in 1898
by Camillo Golgi,
an Italian biologist
 Receives materials
from ER.
 It separates or sorts
proteins and lipids
received from
endoplasmic reticulum
(ER).
 It modifies molecules.
 It packages materials into
vesicles.
(Sorting, modifying and
packaging)
Lysosomes
(suicide bags in the cell)
 Lysosomes are
small spherical
bags surrounded by
a single membrane.
 Lysosomes contain
digestive enzymes.
 Digest food particles in
the cell
 Break down unwanted
substances
 Digest poorly working or
malfunctioning organelles.
Centrioles
(Found only in animal cells,
NOT in plant cells)
 Centrioles are
hollow and
cylindrical
structures
consisting of nine
triplets of
microtubules.
 Play a role in cell division
by producing spindle
fibers.
 Help cell division in
animal cells
Mitochondria
(singular: mitochondrion)
Mitochondria contain DNA
and enzymes called ATP-
synthase
 Mitochondria are
rod-shaped with
double membrane
bounded organelles
found in the
cytoplasm of most
eukaryotic cells.
 The inner folded
membrane of the
mitochondria is
called cristae and
contain a fluid
called matrix.
 Contains enzymes
responsible for
synthesis of energy
for the cell.
 Site of energy production
in the cell
(Power house of the cell)
 Produces ATP in which
energy for cell activities is
stored.
(Site of many biochemical
reactions of aerobic
respiration)

Form 4 Biology
Chloroplast
(contains its own DNA)
 Chloroplasts are
double membrane
bounded organelles
found only in plant
cells, not animal
cells
 Chloroplast
contains a
pigmented
molecule called
chlorophyll that
traps solar energy
for photosynthesis.
 Contains disk-
shaped structures
called thylakoids
 Chloroplast is the site of
photosynthesis.
Chlorophyll:
 Traps sunlight energy
 Makes leaves green in
color.
Note:
 The inner membrane of the chloroplast contains a semi-
fluid material called stroma.
 Stroma contains chloroplast DNA, ribosomes and
enzymes.
 Stroma is the site of independent light reaction for
photosynthesis.
 Thylakoids are site of light dependent reaction of
photosynthesis.
 The stacks of thylakoids are called grana (singular:
granum)
 Lamella connects and separates thylakoid stacks
forming grana.
Vacuole
(Plant cells have large
permanent vacuole, but animal
cells may have small vacuole)
 Vacuole is a space
filled fluid cavity
surrounded by a
membrane called
tonoplast.
 The fluid in the
vacuole is called
cell sap.
 Storage of nutrients and
waste materials.
 Stores water
 Keeps the plant cell turgid

Form 4 Biology
Cytoskeleton  Cytoskeleton is a
network protein
filaments found in
the cytoplasm of
most eukaryotic
cells.
 The three types of
cytoskeleton are:
1. Microtubules
(tubulin)
2. Intermediate
filament
3. Microfilaments
(actin microfilament)
 Allows cell movement
 Allows movement of
organelles within the
cytoplasm.
 Allows movement of
chromosomes of
chromosomes during cell
division.
 Keeps the shape of the
cells
 Supports the cell
 It helps muscle
contraction.
Flagella
(singular: flagellum)
 Flagella are
microscopic hair-
like structures
involved in the
cell locomotion
 Bacteria and
sperm cells have
flagella.
 Movement of the cell

Form 4 Biology
Prokaryotic Cells
(Pro= before, karyon=nucleus)
Eukaryotic Cells
(Eu=true, karyon=nucleus)
Have no true nucleus Have true nucleus
Do not contain membrane bounded
organelles
Contain membrane bounded organelles
Smaller Larger
Ribosomes are small Ribosomes are larger
Cell wall is present Some contain cell wall e.g. plant cells, but
not animal cells
DNA is circular without proteins DNA is linear with proteins
No mitochondria Contain mitochondria
No cytoskeleton Have cytoskeleton
Contain plasmid Do not contain plasmid
Example, bacterial cell Example, plant and animal cells

Form 4 Biology
Part One: Multiple Choice Questions
1. The smallest structural and functional unit of an organism is called
A. Organelle
B. Organ
C. Cell
D. System
2. Which of the following structures serves as the cell’s boundary from its
environment?
A. Mitochondria
B. Cell membrane
C. Chloroplast
D. Channel proteins
3. Which organelle is responsible for the control of cell reproduction?
A. Nucleus
B. Ribosomes
C. Mitochondria
D. Golgi apparatus
4. The diagram below shows a cell.
The function of structure X is to
A. Control cell activities
B. Keep the cell turgid
C. Control entry and exist of material
D. Release energy from glucose
5. Which of the following is not surrounded by a membrane?
A. Nucleus
B. Ribosome
C. Chloroplast
D. Mitochondria

Form 4 Biology
6. Which labeled structure is the chloroplast?
7. Which of the following organelles synthesizes proteins?
A. Mitochondria
B. Golgi body
C. Ribosome
D. Lysosomes
8. In what plant cell structure is water stored?
A. Chloroplast
B. Cell wall
C. Vacuole
D. Cytoplasm
9. A group of similar cells combined together to do the same function is called
A. Tissue
B. System
C. Cell
D. Organ
10.Which of the following organelles is the site where most chemical reactions take
place?
A. Nucleus
B. Ribosome
C. Cytoplasm
D. Nucleolus
11.Which cell structure receives materials from endoplasmic reticulum (ER) for
modifying and packaging?
A. Mitochondria
B. Cell membrane
C. Golgi body
D. Nucleus

Form 4 Biology
12.The below diagram is about an animal cell.
What is the role of the labeled structure W?
A. Control center of the cell
B. Keeps the cell turgid
C. Controls cell activities
D. Controls in and out of the cell
13.Plant cell walls are made up of
A. Cellulose
B. Glycogen
C. Starch
D. Protein
14.What captures energy from sunlight to make food?
A. Cell membrane
B. Cytoplasm
C. Chloroplast
D. Cell wall
15.Structure commonly found in animal cells, but rarely in plant cells, is
A. Golgi apparatus
B. Nucleus
C. Centriole
D. Mitochondria
16.Which cell structure stores food, water and wastes?
A. Ribosome
B. Golgi body
C. Vacuole
D. Lysosome
17.The site where proteins are made is
A. Lysosomes
B. Vesicles
C. Mitochondria
D. Ribosome
18.Which cell organelle directs all activities of the cell?
A. Chloroplast
B. Nucleolus
C. Nucleus
D. Mitochondria

Form 4 Biology
19.Which cell structures can be found in plant cells but not in animal cells?
A. Nucleus, cell wall
B. Chloroplast, mitochondria
C. Cell wall, cell membrane
D. Chloroplast, cell wall
20.The Primary function of the cell wall is to
A. Store DNA
B. Direct activities of the cell
C. Support and protect the cell
D. Help the cell move
21.Which cell organelle is responsible for breaking down or digesting substances?
A. Rough ER
B. Smooth ER
C. Nucleus
D. Lysosome
22.Rough endoplasmic reticulum (RER)
A. Transports lipids
B. Site of respiration
C. Transports proteins
D. Regulates movement
23.Animal cells __________
A. Have definite shape
B. Lack plasmodesmata
C. Chloroplast present
D. Are large size
24.The major component of cell wall in plant is
A. Glycogen
B. Cellulose
C. Water
D. Starch
25. Smooth endoplasmic reticulum (SER)
A. Transports proteins
B. Site of respiration
C. Synthesis lipids
D. Synthesis proteins
26. Ribosome occur in
A. Only eukaryotic plant cells
B. Only eukaryotic plant cells
C. All eukaryotic cells
D. Both prokaryotic and eukaryotic cells
10

Form 4 Biology
27.Which of the following types of molecules are the major structural components of
the cell membrane?
A. Phospholipids and cellulose
B. Nucleic acid and proteins
C. Phospholipids and proteins
D. Proteins and cellulose
28.In multi-cellular organism, the cell is unit of structure and also a unit of
A. Organization
B. Function
C. Strength
D. Foundation
29.Cytoplasm _____
A. is only found in animal cells
B. is important in initiating cell division
C. is the place where chromosomes are found
D. is the place where many chemical reaction occur
30.The structure that plays a role in cell division by producing spindle fibers is
A. Golgi apparatus
B. Centriole
C. Lysosome
D. Ribosome
31.A major difference between prokaryotic and eukaryotic cells is that
A. Prokaryotic cells have a flagellum
B. Eukaryotic cells have a nucleus
C. Prokaryotic cells have cytoplasm
D. Eukaryotic cells have ribosomes
32.Which of the following is true about the nucleus?
A. All cells have a nucleus
B. The nucleus contains all the cell’s DNA
C. The nucleus is considered the control center of the cell
D. All of the above
33.Which of the following is not true about the cell wall?
A. is made up of cellulose
B. is a living part of the cell
C. is found in plant cells
D. gives shape to the plant cells
34.Which of the following is the correct order of organization from simple to complex
A. Cell, organ, tissue
B. Tissue, cell, organ
C. Organ, cell, tissue
D. Cell, tissue, organ
11

Form 4 Biology
35.Plant and animal cells are eukaryotic. This means they ______
A. Are able to multiply
B. Contain DNA
C. Produce energy
D. Have a nucleus
36.Which of the following structures is found in both plant and animal cells?
A. Cell wall
B. Chloroplast
C. Mitochondria
D. Large vacuole
37.What is the function of the cytoplasm
A. Stores water and mineral ions
B. Metabolic reactions occur in it
C. Control what enters and leaves the cell
D. Controls the actions of mitochondria
38.The cell theory states that
A. All organisms are made of one or more cells
B. All cells come from already existing cells
C. Cell is the smallest structural and functional unit of
organisms
D. All of the above
39.All the cells have the following, except
A. Cytoplasm
B. Genetic material
C. Plasma membrane
D. Nucleus
40.All of the following statements are about chloroplast and
mitochondria, except
A. Both use proton gradients for ATP production
B. Both capture light energy
C. Both contain DNA
D. Both are bounded by two unit membranes
12

Form 4 Biology
Part Two: Structured Questions
1. The diagrams below show a plant cell and an animal cell.
(a) Name the parts labeled A, B, C, D, E and F
A. …………………..
B. ………………….
C. ………………….
D. …………………
E. ………………….
F. …………………..
(b) (i) Which of the two cells is a plant cell?
……………………………………………………………………………..
(ii) Give two reasons for your choice.
1. …………………………………………..
2. …………………………………………….
(c) Give one function of
(i) Part B ……………………………………………………………
(ii) Part C …………………………………………………………..
(iii) Part E …………………………………………………………..
(iv) Part A ……………………………………………………………
(d) Give the letters of two parts that are present in plant cells but not in animal
cells.
……………………………….. And ……………………………………………..
(e) Which part of the cell
i. controls the passage of substances in and out of the cell.
……………………………………………………………..
ii. is filled with cell sap.
……………………………………………………………
13

Form 4 Biology
2. With reference to plant cells, complete the table below by writing the name of the
structure in column B that corresponds to the description in column A.
3. The diagram below shows a cell.
(a) Name the structures labeled A and B
A. ……………………………………..
B. ………………………………………
(b) The cell in the diagram is an animal cell.
How can you tell it is an animal cell and not a plant cell? Give two reasons.
1. ……………………………………….
2. ……………………………………..
(c) Oxygen will diffuse into the cell in the diagram. Why? Use information from
the diagram.
………………………………………………………………………………………….
14

Form 4 Biology
4. Complete the table below which compares the structure of typical plant, animal
and prokaryotic cells.
5.
(a) State three differences between plant and animal cells
Plant cells Animal cells
1
2
3
(b) What is the job (role) of each of the following parts of a cell?
i. Nucleus …………………………………………………………….
ii. Cellulose cell wall ………………………………………………….
iii. Cytoplasm …………………………………………………………
iv. Cell membrane ……………………………………………………
(c) i. What substance is contained in the chloroplast?
………………………………………………………………………………………….
ii. Why is this substance important to all living things?
………………………………………………………………………………………..
6. State the function of the following terms.
a. Mitochondria ……………………………………………………………………
b. Chloroplast ……………………………………………………………………..
c. Nucleolus ………………………………………………………………………
d. Golgi apparatus …………………………………………………………………
e. Flagellum ……………………………………………………………………….
15

Form 4 Biology
7. The figure below is a diagram of cell as seen under light microscope.
(A) Name the structures that show that this is a plant cell
and not an animal cell.
A. …………………………….
B. …………………………….
C. ………………………………
(B) Name one chemical compound that is only found in the
structure labeled ‘A’ and state its functions.
………………………………………………………………
……………………………………………………………..
(C) What is the main chemical compound found in the
structure labeled ‘C’? State its functions.
……………………………………………………………..
………………………………………………………………
(D) Name the fluid found in part labeled ‘B’ and state its function
…………………………………………………………………………..
…………………………………………………………………………
(E) Name the structure that contains most of the cellular DNA
……………………………………………………………………………
8. The diagram shows a plant cell. Some structures in the diagram are also found in
animal cells.
16

Form 4 Biology
9. In the table below, column 1 gives description of organelles found in eukaryotic
cells. Complete the table by writing the name of the organelle in column 2
10.Complete the table below by matching the parts of the cell in column A and its
correct function in column B by using letters.
17

Form 4 Biology
1 2 3 4 5 6 7 8 9 10
C B A A B A C C C C
11 12 13 14 15 16 17 18 19 20
C D A C C C D C D C
21 22 23 24 25 26 27 28 29 30
D C A B C D C B D B
31 32 33 34 35 36 37 38 39 40
B C B D D C B D D B
Note: There may also be other possible answers for some questions.
1.
(a) .
A. Cell membrane
B. Cytoplasm
C. Nucleus
D. Cell wall
E. Chloroplast
F. Vacuole
(b) .
(i) Cell Y is a plant cell
(ii) Reasons: 1. Cell Y contains chloroplast 2. Cell Y contains cell wall
(c) .
(i) Part B:site of most chemical reactions in the cell
(ii) Part C:control center of the cell
(iii) Part E:photosynthesis
(iv) Part A:controls movement of substances in and out of the cell
(d) Chloroplast and cell wall
(e) .
(i) A (cell membrane)
(ii) F (vacuole)
ANSWER SHEET FOR PART ONE: MULTIPLE CHOICE QUESTIONS
ANSWERS FOR STRUCTURED QUESTIONS
18

Form 4 Biology
2. .
3.
(a) A. Nucleus B. Cell membrane
(b) Reasons: 1. It does not contain chloroplast 2. It does not contain cell wall
(c) Because there is higher oxygen concentration outside the cell
4.
5.
(a)
Plant cells Animal cells
1 Have cell wall No cell wall
2 Have chloroplast No chloroplast
3 Have large permanent vacuole have small vacuole
(b)
i. Nucleus: control center of the cell (controls cell activities)
ii. Cellulose cell wall: support and protection
iii. Cytoplasm: site of chemical reactions in the cell
iv. Cell membrane: controls movement of substances in and out of the cell
(c)
i. Chlorophyll
ii. Because it produces oxygen and glucose (food) which are important
for all living things.
19

Form 4 Biology
6.
a. Mitochondria: power house of the cell (produces energy)
b. Chloroplast: photosynthesis
c. Nucleolus: synthesis ribosomes
d. Golgi apparatus: it modifies molecules, or it packages materials into vesicles
e. Flagellum: movement of the cell
7.
(A)
A. Vacuole
B. Chloroplast
C. Cell wall
(B) Chlorophyll. It traps light energy. It makes leaves green in color
(C)Cellulose. It supports the plant cell
(D)Cell sap. It stores nutrients and waste materials. Or it stores water
(E) Nucleus
8.
a)
9.
10.Matching column A and column B
a) -------- 4
b) -------- 1
c) -------- 3
d) -------- 5
e) --------- 2
END
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Cell Biology Summary Notes with Somaliland Form 4 Biology Past Exam Practices and Answer Key by Ahmed Omaar

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