ICSE Solutions for Chapter 2 Cell: The Unit of Life Class 9 Biology Selina

Progress Check

1. Name the following:

(i) The kind of microscope that consists of a single biconvex lens

(ii) The kind of mirror used for throwing light on the object in Hooke’s microscope

Solution

(i) Simple/Dissecting microscope

(ii) A concave mirror is used for throwing light

2.What is the maximum magnification that can usually be achieved by

(i) A compound microscope,

(ii) An electron microscope?

Solution

The maximum magnification that can be achieved by the following are:

(i) Compound Microscope: It magnifies an object up to 2000 times.

(ii) Electron Microscope: It magnifies an object up to 200,000 times.

3. Name the following:

(i) Any two one-celled organisms.

(ii) The longest cells in the animals.

(iii)Amoeboid cells in humans.

(iv) Shape of white blood cells.

(v) A cell component which is visible only in cell division stages.

Solution

(i) Chlamydomonas, amoeba.

(ii) The longest cell in animals is the nerve cell

(iii) White blood cells are amoeboid cells in humans that can squeeze out through the capillary walls.

(iv) The shape of white blood cells is amoeboid

(v) Chromosomes are a component of cell that appears in cell division stages only. They otherwise exist only as fine chromatin threads.

4. List three categories of substances which are ensured greater diffusion due to large surface/volume ratio of the cells.

Solution

The three groups of substances that exhibit greater diffusion because of larger volume/surface ratio of cells are listed below:

Oxygen and carbon dioxide- the respiratory gases are diffused in and out of the alveoli
The unwanted metabolic waste produced by the cells to its exterior.
Absorption of nutrients from finger like projections- villi of the small intestine

5. Name the part of the cell in which:

(i) Many chemical reactions occur with the help of the enzymes.

(ii) A network of chromatin fibers occurs.

(iii) Cellulose forms the main component.

Solution

The parts of the cell in which the following reactions occur are as follows:
(i) In plant cells, Cytoplasm is the site in the cell wherein multiple chemical reactions take place the presence of enzymes, whereas in animal cells the site in the cell in protoplasm.

(ii) The site in the cell where a network of chromatin fibers occur is the nucleus.

(iii) The cell wall in the plant cell.

6. Differentiate between

(i) an organ and an organelle

(ii) a plant cell and an animal cell pertaining to the presence of plastids.

Solution

The differences are as follows:

(i) Difference between an organ and organelle

Characteristic	Organ	Organelle
Location	They are present throughout the body.	Known as little organ, are found within cells.
Size	Visible to the naked eyes, larger in size.	Microscopic
Function	Carry out functions of the entire body.	Carry out functions within the cells.
Example	Heart, Lungs, Liver	Ribosomes, Endoplasmic Reticulum, Golgi complex

(ii) Difference between a plant cell and an animal cell pertaining to the presence of plastids

Characteristic	Plant cell	Animal Cell
Presence of Plastids	They contain plastids.	They do not have
Types of Plastids	There are four forms of plastids, namely Chloroplasts, Chromoplasts, Leucoplasts, Gerontoplasts.	Don’t have plastids.

7. Name the cell organelles concerned with

(i) Secretion of enzymes

(ii) Trapping of solar energy

(iii) Synthesis of proteins

(iv) Intracellular digestion

(v) Production of ATP

Solution

The cell organelles concerned with the following are:

(i) Golgi apparatus is responsible for secretion of enzymes and hormones.

(ii) Plastids, in particular, the Chloroplasts are responsible to trap solar energy for the process of photosynthesis as they contain the green pigment- chlorophyll.

(iii) Ribosomes are concerned with the protein synthesis

(iv) Lysosomes are responsible for the intracellular digestion.

(v) Mitochondria often referred to as the ‘power house of the cell’ is responsible for the production of ATP.

8. Name the cell part which is

(i) composed of cellulose

(ii) formed of an irregular network of tubular double membranes

(iii) a clear space with water or other substances in solution

Solution

(i) The cell wall is composed of cellulose.

(ii) The Endoplasmic reticulum is formed of an irregular network of double membrane tubules

(iii) Vacuoles are the clear spaces with water or other substances in solution.

10. Mention if the following statements are true or false. If false, suggest the change in the information underlined.

(i) Prokaryotic cells have larger ribosomes.

(ii) Eukaryotic cells have mitochondria.

(iii) Amoeba is an example of Prokaryotes.

(iv) Bacteria have no nuclear membrane but possess chloroplasts.

Solution

(i) The statement is false. Prokaryotic cells have a small ribosome.

(ii) The statement is true.

(iii) The statement is false. Amoeba is an example of eukaryotes.

(iv) The statement is false. Bacteria are prokaryotes, they do not have any other membrane bound organelles. They do not contain chloroplasts but possess bacterio chlorophyll.

11. Column I lists a few activities of living organisms and column II the activity of cells related to them. Match the items in the two columns.

Column I (Activity of organism)	Column II (Activity of cells)
(i) Repair	(a) Contractility of cells
(ii)Cooling of body	(b) Cells devour germs
(iii)Movement	(c) Cell division
(iv)Protection from diseases	(d) Gland cells give out sweat for evaporation

Solution

Column I (Activity of organism)	Column II (Activity of cells)
(i) Repair	(c) Cell division
(ii)Cooling of body	(d) Gland cells give out sweat for evaporation
(iii)Movement	(a) Contractility of cells
(iv)Protection from diseases	(b) Cells devour germs

12. Which cell organelle is the key to the life of the cell?

Solution

The nucleus is the key to the life of the cell. It regulates the functions of the cell. It contains the genes, which control heredity characters and governs critical life processes such as reproduction and growth of the cell. It functions as a control centre.

13. How do you say that a cell also has a life span and death like an organism? Give one example.

Solution

Cells are structural and functional living entities. It consists of organelles that undergo respiration and eliminate waste. They have a life span that is definite. As living entities are not immortal and die at a certain point in time, cells also die. Death of cells in human body takes place every second. Because of the presence of cell organelles namely, lysosomes (suicidal bags) and mitochondria (respiration centre) we can deduce that cells have a life span and death as seen in a living entity. Lysosomes present in the cell age, deteriorate get damaged and die through a process known as apoptosis.

14. All organisms excrete. Does an individual cell also do it? Give one example.

Solution

Excretion is a biological process and is essential to get rid of harmful substances. The process is exhibited by every living entity. The ingested food is digested and elimination of undigested wastes and toxic substances takes place from the body of the entity. Since a cell is living, it excretes wastes.

Example: Amoeba possess contractile vacuole that assembles wastes and water generated by the body, swells up and surfaces up to bursts liberating contents to the outwards.

15. Every organism needs food. Does a cell also need it? Explain very briefly.

Solution

Yes, cell requires food. Energy is required by all living entities, be it single-celled or multicellular entities. They need energy to survive and grow which is obtained from the food ingested. This energy is utilized to perform various functions such as maintenance of cell organelles, their proper functioning and also promote functioning of other cells involved in digestion, movement etc.

Review Questions

A. Multiple Choice Type

1. Which one of the following cell organelles is correctly matched with its function?

(a) Ribosomes — Synthesis of proteins

(b) Mitochondria — Secretion of enzymes

(c) Plasma Membrane — Freely permeable

(d) Centrosome — Carries genes

Solution

(a) Ribosomes- synthesis of proteins

Ribosomes are small granules scattered in the cytoplasm, responsible for protein synthesis.

2. All life starts as

(a) An egg

(b) A single cell

(c) A gene

(d) A chromosome

Solution

(b) A single cell.

All living entities including humans start life as a single cell known as the zygote.

3. Which one of the following is found both in cells of a mango plant and a monkey?

(a) chloroplasts

(b) centrioles

(c) cell wall

(d) cell membrane

Solution

(d) cell membrane

Cell membranes are found both in mango plant (plant cell) and monkey (animal cells).

4. A plant cell can be identified from an animal cell by the:

(a) Absence of centrosome

(b) Presence of cell membrane

(c) Presence of vacuoles

(d) None of the above

Solution

(a) Absence of centrosome

Centrosomes are regions girdling the centrioles, located near the nucleus. They are present inanimal cells.

5. Plant cell has a cell wall made of:

(a) Protein

(b) Fructose

(c) Cellulose

(d) Fatty acids

Solution

The cell wall of plant cells is made up of cellulose.

6. The cell organelle that helps in respiration of the cell is:

(a) Mitochondria

(b) Lysosome

(c) Ribosome

(d) Centrosome

Solution

(a) Mitochondria

Mitochondria are involved in cellular respiration.

B. Very Short Answer Type

1. Name the part of the cell concerned with the following?

(a) Liberation of energy

(b) Synthesis of proteins

(c) Transmission of heredity characters from parents to offspring

(d) Initiation of cell division

(e) Hydrolytic in function

(f) Entry of only certain substances into and out of the cell.

Solution

(a) Liberation of energy - Mitochondria

(b) Synthesis of proteins - Ribosomes

(d) Initiation of cell division - Centrosome

(e) Hydrolytic in function - Lysosomes

(f) Entry of only certain substances into and out of the cell - Plasma membrane/cell membrane

2. State whether the following statements are true(T) or false(F):

(a) All animal cells contain a cell wall. T/F

(b) The cell wall is made of protein. TF

(c) Centrosome occurs in animal cells T/F

(d) Plant cells contain large vacuoles. T/F

(e) Protoplasm is the part of the cell which surrounds the nucleus T/F

(f) Genes are located in chromosomes. T/F

(g) Anthocyanins are the pigments of flowers, which are dissolved in cell-sap. T/F

Solution

(a) False

(b) False. The cell wall in plant cells is made up of cellulose.

(d) True

(e) False. Cytoplasm is the protoplasm of the cell surrounding the nucleus.

(f) True

(g) True

3. How many chromosome pairs are found in human cells?

Solution

Each cell in humans has 23 pairs of chromosomes, 46 in total. Out of this, 22 pairs of chromosomes are autosomes — same in both males and females. The last pair of chromosomes is the sex chromosome and differs in males (XY) and females (XX).

4. What is the name of the chemical substance which constitutes the genes?

Solution

The chemical substance constituting the genes is DNA. It stands for de-oxy ribonucleic acid.

5. Match the items in column ‘A’ with those in column ‘B’

Column A	Column B
(a) Vacuoles	(i) Intracellular digestion
(b) Nucleolus	(ii) respiratory enzymes
(c) Lysosomes	(iii) Covered by tonoplast
(d) Anthocyanin	(iv) Dissolved in the cytoplasm
(e) Cristae	(v) Forms RNA

Solution

Column A	Column B
(a) Vacuoles	(iii) Covered by tonoplast
(b) Nucleolus	(v) Forms RNA
(c) Lysosomes	(i) Intracellular digestion
(d) Anthocyanin	(iv) Dissolved in the cytoplasm
(e) Cristae	(ii) respiratory enzymes

6. Fill in the blanks:

(a) _____ consists of membranous sacs and secretes 40 types of digestive enzymes.

(b) _____ sis surrounded by microtubules, located near the nucleus

(c) Very thin flexible, living membranes which is differently permeable, is called ____

(d) More than 1000 chromosomes are found in the nucleus of certain _____

(e) _____ are heredity units.

(f) _____ is a plastid which stores starch.

Solution

(a) Lysosomes

(b) Centriole

(d) Insects

(e) Genes

(f) Leucoplast

C. Short Answer Type

1. It is said that the protoplasm cannot be analysed chemically. Why?

Solution

Protoplasm is the living matter of the cell. Protoplasm cannot be analysed chemically because the chemical composition of protoplasm is very complex. It varies slightly from one cell to another, although the common elements included in the composition of protoplasm such as carbon, hydrogen, oxygen, nitrogen, sulphur, iron and phosphorus are still the same in all the cells.

2. What is the difference between an organ and an organelle?

Solution

Characteristics	Organ	Organelle
Size	Visible to the naked eyes, larger in size	Microscopic
Location	They are present throughout the body.	Known as little organs and found within the cell
Function	Carry out functions of the entire body.	Carry out functions within the cell.
Example	Heart, Lungs, Liver	Ribosomes, Endoplasmic reticulum, Golgi complex

3. Do you think the cells of an elephant would be larger than the cells of a rat? Explain briefly.

Solution

The cells of an elephant would be of the same size as the cells of a rat. The size of cells does not vary within the organisms, however, the number of cells varies from one organism to another. A larger animal like an elephant will have more number of cells as compared to a smaller animal like a rat. However, the size of the cell will be the same.

4. Differentiate between the following pairs of terms:

(a) Protoplasm and cytoplasm

(b) Nucleolus and nucleus

(c) Centrosome and chromosome

(d) Cell wall and cell membrane

(e) Plant cell and animal cell

(f) Prokaryotes and eukaryotes

Solution

(a) Difference between Protoplasm and cytoplasm

Protoplasm	Cytoplasm
Protoplasm is the living matter of the cell. The total substance of a living cell i.e. nucleus and cytoplasm.	Mixture of insoluble and soluble organic compounds and water wherein different cell organelles are implanted.

(b) Difference between Nucleolus and nucleus

Nucleolus	Nucleus
It is present in the nucleus and is round-shaped nucleoli.	It is present in the cell and is a dense spherical structure. It comprises a network of thread-like structures known as chromatin fibres.

Centrosome	Chromosome
It is a clear area of the cytoplasm close to the nucleus from which spindle fibres develop during cell division.	They contain genes or hereditary data that transfer genetic traits from parents to offspring.
Centrosome is found only in an animal cell.	Chromosomes are found in nucleus of both animal and plant cell.

(d) Difference between Cell wall and Cell membrane

Cell Wall	Cell Membrane
It is a non-living rigid layer.	It is a living, thin and flexible membrane.
It is made up of cellulose.	It is made up of lipoproteins.
It is freely permeable.	It is semi-permeable.

(e) Difference between Plant cell and Animal cell

Plant Cell	Animal Cell
Cell wall is present.	Cell wall is absent.
Centrosome is absent.	Centrosome is present.
Vacuoles are large and prominent.	Vacuoles are small and temporary.
Plastids are present.	Plastids are absent.
Cell wall is made up of cellulose.	No cell wall is present.

(f) Difference between Prokaryotes and Eukaryotes

Prokaryotes	Eukaryotes
Organisms with cells containing a primitive, undefined nucleus are called prokaryotes.	Organisms with cells containing a well-defined nucleus with a nuclear membrane are eukaryotes.
They contain small ribosomes.	They contain larger ribosomes.
They lack other cell organelle.	They contain other cell organelle.
Examples: Bacteria, blue-green algae etc.	Examples: Euglena, Human Beings.

5. Mention three features found only in plant cells and one found only in animal cells.

Solution

Features that are observed only in plant cells:

(i) Cell wall

(ii) Plastids

(iii) Large vacuoles

Features that are observed only in animal cells:

(i) Presence of Centrosomes.

6. Why are the cells generally of a small size?

Solution

Cells are smaller in size because:

(i) To enable different regions of the cell to communicate with each other rapidly for the cell to function effectively.

(ii) To have a large surface area is to volume ratio for greater diffusion of substances, in and out of the cell.

D. Long Answer Type

1. What is the cell theory? Who propounded it and when?

Solution

Postulates of cell theory:

(i) Cell is the smallest unit of structure of all living things.

(ii) Cell is the unit of function of all living things.

(iii) All cells arise from pre-existing cells.

The theory was propounded in 1839 by Schwann and Schleiden. Rudolf Virchow in 1858 added the last point mentioned above to the cell theory.

2. Mention the three differences between a living cell and a brick in a wall.

Solution

Living cell	Brick in a wall
Non-rigid living structure.	Rigid non-living structure.
Mainly composed of cellulose.	Mainly composed of soil.
Freely permeable.	Impermeable.

3. Name the plastid and pigment likely to be found in the cells of:

(a) Petals of sunflower

(b) Ripe tomato

(c) Skin of green tomato

(d) Cells of potato.

Solution

Cells	Plastid	Pigment
(a) petals of sunflower	Chromoplasts	Xanthophyll
(b) ripe tomato	Chromoplasts	Carotene
(c) skin of green mango	Chloroplasts	Chlorophyll
(d) cells of potato	Leucoplasts	No pigment

4. State the major functions of the following:

(a) Plasma membrane

(b) Ribosome

(c) Lysosome

(d) Mitochondria

(e) Golgi apparatus

(f) Cytoplasm

(g) Asters of centrosome

(h) Chromosomes

(i) Glycogen granule

(j) Vacuoles

Solution

(a) Plasma membrane:

(i) Separates contents of the cell from its surroundings

(ii) Regulates the entry of certain solutes and ions

(iii) Maintains the shape of animal cell

(b) Ribosome:

(i) Protein synthesis

(i) Intracellular digestion

(ii) Destroy foreign substances

(iii) When the cell is old or injured, lysosomes rapidly destroy cell organelles and h are called suicide bags.

(d) Mitochondria:

(i) Synthesis of respiratory enzymes

(ii) Release of energy from pyruvic acid produced in cytoplasm in the form of ATP

(e) Golgi apparatus:

(i) Synthesis and secretion of enzymes, hormones, etc.

(ii) Formation of acrosome of sperm

(f) Cytoplasm:

(i) Different organelles contained in it perform different functions.

(ii) All metabolic activities occur in it.

(g) Asters of centrosome:

(i) Initiates and regulates cell division

(ii) Forms spindle fibres

(h) Chromosomes:

(i) Carry genetic characters from parents to offspring

(i) Glycogen granule:

(i) Serves as food for the cell

(j) Vacuoles:

(i) Gives turgidity to the cells

(ii) Storage of water and other substances, food, pigments and waste products

5. List any six features found both in plant and animal cells.

Solution

Six common features found both in plant and animal cells are:

(i) Cell membrane is present

(ii) Golgi body is present

(iii) Liquid matrix known as cytoplasm in the cell

(iv) Mitochondria which generates energy

(v) Ribosomes are found. They are responsible for protein synthesis

(vi) Presence of a prominent nucleus.

E. Structured/Application/Skill Type

1 Given below are the sketches of two types of cells A and B

(a) Which one of these is a plant cell? Give reason in support of your answer.

(b) List the cell structures which are common to both the types

(c) Name the structures found only in plant cells and those found only in animal cells.

Solution

(a) Figure B. displays a plant cell. Some of the reasons given below:

(i) Presence of a cell wall

(ii) Large vacuole

(iii) The vacuole is seen pushing the nucleus to the periphery

(b) Both the cells in the figure have these structures in common:

Nucleus
Mitochondria
Ribosome
Cell membrane
Lysosome
Endoplasmic reticulum
Golgi body

Animal cell — Centrosome

ICSE Solutions for Chapter 2 Cell: The Unit of Life Class 9 Biology Selina

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Selina Concise Ch 2 Cell: The Unit of Life ICSE Solutions Class 9 Biology

ICSE Solutions for Chapter 2 Cell: The Unit of Life Class 9 Biology Selina

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