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Chapter 2
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Suggested answers to Exercise and Reading to
learn
(Note: The overseas examination boards bear no responsibility for the suggested answers
contained in this publication. Answers for HKCEE and HKALE questions are not available due
to copyright restrictions.)
Ch 2 The cell as the basic unit of life
Exercise
Multiple-choice questions (p. 2-30)
1
5
9
13
B
C
B
D
2
6
10
C
A
D
3 D
7 D
11 C
4
8
12
B
B
A
Short questions (p. 2-32)
14
15
(a) Irregular
0.5m
(b) cell wall
0.5m
(c) regular
0.5m
(d) cell wall
0.5m
(e) Absent
0.5m
(f)
0.5m
photosynthesis
(g) centre
0.5m
(h) centre of the cell
0.5m
a
b
A — nucleus
1m
B — cell membrane / plasma membrane
1m
Any one from:
1m
Absorbs light energy for photosynthesis
Absorbs light energy to make sugar / starch / carbohydrate / organic material / food
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Suggested answers to Exercise and Reading to learn
c
Chapter 2
p.2/6
Any two rows from:
Plant cell
- Has vacuole OR has cell sap
- Has cell wall / cellulose
- Stores starch OR does not store
glycogen
Animal cell
- No / small vacuole OR no cell
sap
- No cell wall / cellulose OR only
membrane
- Does not store starch OR stores
glycogen
1m x 2
16
a
i
Part of
cell
X
Name
Nucleus
Y
Cell wall
Z
Cell
membrane
Function
Contains genetic information / genetic
material / DNA / chromosomes
OR
Gives instructions to the cells / controls
cell processes / activities
Maintains cell shape / supports cell /
stops cell bursting
Controls entry and / or exit of
molecules / substances
2m
ii
Plant cells A and B have a cell wall / part Y, cell C / the animal cell does not.
1m
Cells A and B have a (large central) vacuole, cell C / the animal cell does not.
1m
17
b
Glucose / oxygen / sugar
1m
a
b
Cheek cells and onion epidermal cells
Cheek cells, onion epidermal cells and red blood cells
c
None of them
d
Onion epidermal cells and xylem cells
(2m for all correct answers in each part or no marks)
18
a
Remove small bits from the organism and observe under the microscope.
1m
Observe whether the cells had cell walls or not. It was likely to be a plant if the cells
had cell walls.
1m
b
i
Remove small bits from different parts of the organism and observe under the
microscope.
1m
See whether the cells are different in size and shape, and group together.
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1m
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Suggested answers to Exercise and Reading to learn
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Chapter 2
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Organ level of organization — different tissues group together to form an organ
to carry out particular functions.
1m
System level of organization — several organs and tissues work together to form
a system that carries out a particular set of functions in a coordinated way. 1m
19
a
Eyepiece lens
magnification
7X
7X
7X
Objective lens
magnification
10X
20X
40X
Total magnification
70X
140X
280X
0.5m x 2
b
20
a
i
0.1 mm
1m
ii
Plant cells are larger than animal cells.
1m
DNA is present in prokaryotic cells and lying free in the cytoplasm.
1m
DNA in eukaryotic cells is enclosed within the nucleus instead of lying free in the
cytoplasm.
1m
Mitochondria are absent in prokaryotic cells.
1m
The cell wall in prokaryotic cells does not contain cellulose.
1m
The rough endoplasmic reticulum in eukaryotic cells is used for synthesizing protein.
1m
b
Both prokaryotic and eukaryotic cells are bounded by a cell membrane.
1m
Their genetic material exists in the form of DNA.
1m
Structured questions (p. 2-33)
21
a
i
ii
b
Substance B
1m
It contains carbon, oxygen and hydrogen only.
1m
Fats and oils — act as an energy reserve
1m
Phospholipids — make up cell membranes
1m
Protein
1m
It contains carbon, hydrogen, oxygen, nitrogen and sulphur which are the composition
of proteins.
1m
c
Nucleic acid
1m
Inside the nucleus (for DNA and RNA) and the cytoplasm (for RNA) of a eukaryotic
cell or the cytoplasm of a prokaryotic cell.
1m
22
a
A — cell membrane
B — cytoplasm
C — nucleus
D — chloroplast
E — vacuole
b
1m x 5
Cell wall
1m
It supports and gives the shape to the plant cell / protects the cell.
1m
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c
d
23
a
b
Chapter 2
p.4/6
Title
0.5m
Magnification
0.5m
Original magnification is 10X × 4X = 40X
0.5m
New magnification is 5X × 10X = 50X
0.5m
The cell will appear larger under a higher power of magnification.
1m
A — cell membrane
1m
It controls the movement of materials into and out of the cell.
1m
B — cytoplasm
1m
It provides a place for cellular chemical reactions to take place.
1m
Cell X — green leaf cell
0.5m
Cell Y — chicken blood cell
0.5m
Reasons: (any 2, 1m each)
Cell X is rectangular.
Cell X contains oval structures which are most likely chloroplasts.
c
Cell X is covered by a cell wall.
2m
i
1m
Scale = 45 : 0.1
Magnification =
24
a
1m
450
= 15
30
ii
Magnification of the eyepiece =
i
A — nucleus / nucleolus
1m
B — ribosomes
1m
C — mitochondrion
1m
Present in a prokaryotic cell — B
1m
Absent from a prokaryotic cell — A / C
1m
i
Can see detail of mitochondria, ribosome and nuclear membrane
2m
ii
B; for protein / polypeptide synthesis
1m
C; for ATP production / energy release
1m
ii
b
45
= 450
0 .1
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Chapter 2
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Essays (p. 2-35)
25
Water makes up the largest percentage by weight of most organisms.
It serves for many functions in the body:
Water is a good solvent for many substances.
0.5m
It dissolves various substances and provides the medium for chemical reactions to take
place in cells.
1m
It also acts as a transport medium. For example, water is the major component of blood
which carries nutrients and many other substances throughout the body.
1m
Water removes heat by evaporation.
0.5m
It acts as a cooling agent to help regulate body temperature through sweating in mammals
and transpiration in plants.
2m
Water is the reactant in some chemical reactions.
1m
For example, carbon dioxide and water are the reactants in photosynthesis.
They react to produce oxygen and food in the presence of light and chlorophyll.
OR Water acts as a reactant in breaking down certain complex food substances during
digestion of food.
1m
26
Water gives shape and support to organisms.
1m
Plant cells become turgid when they are full of water. This gives support to young
seedlings.
1m
Water provides buoyancy for plants and animals in water.
1m
The microscopes enable us to observe and understand the following:
Cell structures
2m
Tissue structures, e.g. histology of digestive system related to function, muscle structure,
kidney tubules, leaf structure, etc.
2m
Biological processes, e.g. cell division, fertilization, capillary circulation, etc.
2m
Whole organisms and their classification, e.g. bacteria and viruses, taxonomic differences
in small organisms.
2m
Other uses, e.g. understanding effects of disease / cancer, opportunities to improve/alter
living organisms.
2m
Reading to learn (p. 2-36)
1
2
Leeuwenhoek was skilful and hard-working.
1m
He was curious about the things around him.
1m
Leeuwenhoek was interested in Robert Hooke’s work.
1m
The work published by a scientist can inspire other scientists to do further research.
Scientists always build on the work of other scientists.
2m
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Chapter 2
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Leeuwenhoek’s discovery of microorganisms is more important. His observations opened
the scope of the microbial world to the scientists. These laid the foundation for various
fields of biology, like bacteriology and microbiology.
(accept other reasonable answers)
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2m