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CELL – STRUCTURE
AND FUNCTIONS
TEXTBOOK QUESTIONS AND THEIR ANSWERS
Q.1. A hen’s egg can be seen easily by naked eyes. Is it a cell or
a group of cells?
Ans. Though the egg of a hen is big enough to be seen by the
unaided eye, but it is not a group of cells. It is a single cell.
Q.2. How do you define the shape of amoeba in the figure?
Ans. Amoeba has no definite shape. It keeps on changing its shape.
Q.3. What advantage does amoeba derive by changing its
shape?
Ans. The change in shape is due to the formation of pseudopodia
which facilities movement and help in capturing food.
Q.4. What do you observe when you remove the shelf of a boiled
egg of hen?
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Ans. A white material surrounding the yellow part. Yellow part of
the egg is yolk while the white material is albumin. It is a
single cell.
Q.5. Are the cells in an elephant larger than the cells in a rat?
Ans. No, the size of the cells has no relation with the size of the
body of the animal. It is related to its function.
Q.6. Boojho want to know why plant cells need cell walls?
Ans. Cell wall is the outer thick layer in cells of plant.
Plant cells need cell wall because it provides the protection
against variation in temperature, high wind-speed, atmospheric
moisture, etc.
Q.7. Draw and label the diagram of human cheek cells.
Ans.
Q.8. What is absent in animal cells but present in plant cells?
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Ans. A cell wall, is absent in animal cells.
Q.9. Paheli wants to know if the structure of the nucleus is the
same in cells of plants, animals and bacteria?
Ans. The nucleus of bacterial cell is not well organiased. There is
no nuclear membrane. So, the cells having nuclear material
without nuclear membrane are termed as prokaryotic cells.
Therefore, bacteria is a prokaryote.
Plants and animals both have well organized nucleus and
nuclear membrane. So, these are eukaryotes.
Q.10. Tabulate the similarities and dissimilarities of plant and
animal cells.
Ans.
Sl. No.
Part
Plant Cell
Animal
Cell
1.
Cell membrane
Present
Present
2.
Cell wall
Present
Absent
3.
Nucleus
Present
Present
4.
Nuclear membrane
Present
Present
5.
Cytoplasm
Present
Present
6.
Plastids
Present
Absent
7.
Big Vacuoles
Present
Present
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Q.11. Indicate whether the following statements are True (T) or
False (F).
(a) Unicellular organisms have one-celled body.
(b) Muscle cells are branched.
(c) The basic living unit of an organism is an organ.
(d) Amoeba has irregular shape.
Ans. (a) True, (b) True, (c) False, (d) True.
Q.12. Make a sketch of the human nerve cell. What function do
nerve cells performs?
Ans. Functions of human nerve cell :
(i) Nerve cells receive message from different parts of body.
(ii) They further transfer these message to brain and brain
further send commands for functioning of different organs.
(iii) They coordinate functioning of different organs of body.
Q.13. Write short notes on the following:
(a) Cytoplasm
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(b) Nucleus of a cell
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Ans. (a) Cytoplasm : Cytoplasm is a jelly-like substance present
between the cell membrane and the nucleus. Various other
organelles of cells are present in the cytoplasm. Cytoplasm
is made up of chemical substances like carbohydrates,
proteins and water. Many chemical reactions such as
breakdown of food or synthesis of food take place in it.
(b) Nucleus of a cell : Nucleus is the master of the cell. It
commands all the functioning of the cell. It is generally
located in the centre of the cell and is spherical in
structure. A membrane called nuclear membrane separates
it from cytoplasm. Nucleus contains a smaller spherical
body called nucleolus. In addition, nucleus also contains
thread like structures called chromosomes. These carry
genes and help in inheritance or transfer of characters
from the parents to the offspring.
Q.14. Which part of the cell contains organelles?
Ans. Cytoplasm.
Q.15. Make sketches of animals and plant cells. State three
differences between them.
Ans.
Plant Cell
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Animal Cell
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1. Cell wall is absent.
1. Plant cell has a rigid cell
wall.
2. Plant cell has chloroplasts.
3. Plant cell lacks
centrosomes.
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2. Chloroplasts are
absent.
3. Centrosomes are
present.
Q.16. State the differences between eukaryotes and prokaryotes.
Ans.
Eukaryotes
Prokaryotes
1. Nucleus is bounded
by nuclear
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1. Nucleus is not bounded by
nuclear membrane.
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membrane
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2. Membrane bound
2. Possess membrane
organelles are absent.
bound organelles.
3. All higher plants
3. Bacteria and blue green
and animals are
algae are prokaryotes.
eukaryotes.
Q.17. Where are chromosomes found in a cell? State their
functions.
Ans. Chromosomes are found in the nucleus of a cell. Their
function is to carry ‘genes’ and help in inheritance or transfer
of characters from the parents to the offspring.
Q.18. ‘Cells are the basic structural units of living organism’.
Explain.
Ans. Cells are similar in basic structure, but attain different shapes
in the different organs. A group of similar cells combine to
form a tissue and many tissues combined together to form an
organ and organ combined to form a organ system/organism.
[Cells → Tissue → Organ → Organ system → Organism.]
So cell is the basic structural unit of an organism. All basic
functions for the survival of an organism take place inside
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cells so, cells are the basic structural units of a living
organism.
Q.19. Explain why chloroplasts are found only in plant cells?
Ans. The chloroplasts green coloured pigments called chlorophyll
which
synthesis
food
in
plants
by
the
process
of
photosynthesis. Since food is manufactured only by plants, so,
chloroplasts are present only in plants.
Q.20. Complete the following crossword with the help of clues
given below :
Across
1.
This is necessary for photosynthesis.
3.
Term for component present in the cytoplasm.
6.
The living substance in the cell.
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8.
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Unit of inheritance present on the chromosomes.
Down wards
1.
Green plastids
2.
Formed by collection of tissues.
4.
It separates the contents of the cell from the
surrounding medium.
5.
Empty space in the cytoplasm.
7.
A group of cells.
Ans.
Across
Down
1.
Chlorophyll ;
1. Chloroplasts
3.
Organelle
2. Organ
6.
Protoplasm
4. Membrane
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8.
Genes
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5. Vacoule
7.
Tissue
Q.21. Find out the diseases which are passed on from parents to
the offspring.
Ans. The disease which are passed on from parents to the offspring,
are called genetic diseases.
1. Colour blindness – The person cannot differentiate redgreen colours.
Reason – It is due to a recessive allele on x-chromosome.
2. Haemophilia – It is a disorder of the blood, where a vital
factor for clotting the blood is absent, hence, clotting is
abnormally delayed and such bleeding may become fatal.
Reason – It is due to a recessive allele on x-chromosome.
3. Albinism – The albinos cannot synthesize skin pigment
melanin, hence they have their iris, hairs and skin without
pigment.
Reason – Such diseases appear when both the parents of
the affected person are heterozygous and carriers of the
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disease, so the parents do not show the disease, but the it
appears in the siblings.
4. Muscular dystrophy – Progressive deterioration of
muscles makes a person invalid at an early age.
Reason – It is due to recessive allele on x-chromosome.
Q.22. Write a short not on ‘genetically modified crops’.
Ans. Genetically modified crops are crops produced from
genetically modified organism that have their DNA altered
through genetic engineering. Genetically modified crops were
first put on the market in the early 1990’s. The most common
modified crops are derived from plants. for eg. soyabean, corn
and cotton seed.
The process involve the DNA from one organism, modified it
in a laboratory and then inserted into the target organism’s
genome to produce new and useful genotype.
Q.23. Find out about Bt cotton from an agriculture expert.
Ans. Bt cotton, a transgenic plant, produces an insect controlling
protein. The gene which has been derived from the naturally
occurring bacterium, Bacillus thuringiensis. The cotton
hybrids containing Bt gene produces its own toxin. Thus
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reducing the use of chemical insecticide and providing a major
benefit to cotton growers and the environment.
Advantages : Bt cotton appears to be safe for the farmers and
for consumers. The toxicity of each Bt type is limited to one or
two insect and is non-toxic to vertebrates and many beneficial
arthopods.
The reason is that Bt works by binding to the appropriate
receptor on the surface of midglit epithelial cells. Any
organism that lacks the appropriate receptors in its gut cannot
be affected by Bt.
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