Selina ICSE Class 9 Biology Solutions Chapter 2 Cell The Unit Of Life

Multiple Choice Questions:-

1) Which of the following cell organelles is correctly matched with its function?
a) Ribosomes → Synthesis of proteins
b) Mitochondria → Secretion of proteins
c) Plasma membrane → Freely permeable
d) Centrosome → Carries genes

2) All life starts as _________.
a) an egg
b) a single cell
c) a gene
d) a chromosome

3) Which one of the following is found both in the cells of a mango plant and a monkey?
a) Chloroplasts
b) centrioles
c) cell wall
d) cell membrane

4) A plant cell can be identified from an animal cell by the:
a) absence of centrosome
b) presence of cell membranes.
c) Presence of vacuoles
d) none of the above

5) A plant cell has a cell wall made of:
a) Protein
b) Fructose
c) cellulose
d) Fatty acid

6) The cell organelle that helps in the respiration of the cell is:
a) Mitochondria
b) Lysosome
c) Ribosome
d) Centrosome

One Word questions and answers

Question 1. Name the part of the cell concerned with the following :

a) Liberation of energy

b) Synthesis of proteins

c) Transmission of hereditary characters from parents to offspring

d) Initiation of cell division

e) Hydrolytic in function

f) The entry of only certain substances into and out of the cell.

Question 2. State whether the following statement of true (T) or false (F):-

1) All animal cells contain a cell wall.

2) The cell wall is made of protein.

3) Centrosome occurs in animal cells.

4) Plant cells contain large vacuoles.

5) Protoplasm is the part of the cell which surrounds the nucleus.

6) Genes are located on a chromosome.

7) Anthocyanins are the pigments of flowers, which are dissolves in cell-sap.

Question 1. Very short answer type:-

1. How many chromosome pairs are found in human cells?
Sol.
Chromosome pairs are found in human cells 23 pairs.

2. What is the name of the chemical substance which constitutes the genes?
Sol.
Deoxyribonucleic acid (DNA) is the chemical substance which constitutes the genes.

Q2. Match the item column A with column B:-

Solution.

Question 3. Fill in the blanks:-

1) _________ consists of membranous sacs and secrets 40 types of digestive enzymes.

2) ________ is surrounded by microtubules, located near the nucleus.

3) Very thin flexible, a living membrane which is differentially permeable, is called__________.

4) More than a thousand chromosomes are found in the nucleus of certain _______.

5) _______ are hereditary units.

6) __________ is a plastid which stores starch.

Question 4. Short answer type:-

Question 1, It is said that the protoplasm cannot be analyzed chemically. Why?
Solution.
Protoplasm is the cell’s life substance. Because protoplasm’s chemical makeup is so complicated, it can’t be studied chemically. It differs somewhat from one cell to the next, although the common components found in protoplasm, such as carbon, hydrogen, oxygen, nitrogen, sulphur, iron, and phosphorus, are present in all cells.

Question 2. What is the difference between an organ and an organelle?
Solution.
Organs are bodily components with a defined shape and structure that perform specialized duties. Cell organelles are similar to cell organelles in that they have a distinct shape and structure and perform unique activities. Organelles have the same status in a cell as organs have in an animal’s or plant’s complete body when it comes to performing certain duties.

Question 3. Do you think the cells of an elephant would be larger than the cells of a rat? Explain briefly.
Solution.
Elephant cells are about the same size as rat cells. The size of cells does not change amongst organisms; nevertheless, the quantity of cells does. A larger animal, such as an elephant, would have more cells than a smaller species, such as a rat. The cell size, however, will remain constant.

Question 4. Distinguish 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) Protoplasm and cytoplasm:-

Question 5. Short answer type:-

1) Why are the cells generally of a small size?
Solution.
Features found only in plant cells:
(i) Presence of cell wall
(ii) Presence of large vacuoles. The liquid contained in vacuoles is called cell sap
(iii) Presence of plastids
Features found only in animal cells:
(i) Presence of centrosome

2) Why are the cells generally of a small size?
Solution.
Cells generally remain small 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

Question 6. 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.
Cell theory was propounded by Theodor Schwann and Matthias Schleiden in the year 1839 and was modified by Rudolf Virchow in 1858.

Question 2. Mention any three differences between a living cell and a brick in a wall.
Solution.

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

Question 4. State the major function of the following:
(a) Plasma membrane
(b) Ribosome
(c) Lysosomes
(d) Mitochondria
(e) Golgi apparatus
(f) Cytoplasm
(g) Asters of centrosome
(h) Chromosomes
(i) Glycogen granule
(j) Vacuoles
Solution.
(a) Plasma Membrane:
(1) Keeps the contents of the cell apart from the environment.
(2) Controls the admission of specific ions and solutes.
(3) Keeps the form of the animal cell.
(b) Ribosome: Protein synthesis
(c) Lysosomes:
(1) Intracellular digestion
(2) Foreign material destruction
(3) When a cell is old or wounded, lysosomes rapidly destroy cell organelles, earning them the nickname “suicide sacks.”
(d) Mitochondria:
(1) Respiratory enzyme synthesis.
(2) Energy is released in the form of ATP from pyruvic acid generated in the cytoplasm.
(e) Golgi apparatus:
(1) Enzyme, hormone, and other chemical synthesis and secretion
(2) Acrosome formation in sperm
(f) Cytoplasm:
(1) It contains several organelles that conduct various activities.
(2) It is where all metabolic processes take place.
(g) Asters of centrosome:
(1) Starts and controls cell division.
(2) Spindle fibres are formed.
(h) Chromosomes: Pass on genetic traits from parents to children
(i) Glycogen granule: The cell uses it as food.
(j) Vacuoles:
(1) Gives the cells turgidity.
(2) Water and other substance storage, as well as food, pigments, and waste products.

Question 5. List any six features found both in plant and animal cells.
Solution.
Below are the features found in both plant and animal cells:-
(1) Cell membrane presence.
(2) The presence of cytoplasm, a liquid matrix in the cell.
(3) The presence of energy-producing mitochondria.
(4) The presence of protein-synthesizing ribosomes.
(5) The Golgi body is present.
(6) The presence of a large nucleus.

Question 7. 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 reasons in support of your answer.
(b) List the cell structures which are common to both types.
(c) Name the structures found only in plant cells and those found only in animal cells.
Solution.
(a) Figure B depicts a plant cell. It has a cell wall and a huge vacuole that pushes the nucleus to the outskirts.
(b) Both kinds share the same cell membrane, ribosomes, nucleus, endoplasmic reticulum, lysosomes, Golgi body, and mitochondria.
(c) Only plant cells include plastids and cell walls. Only animal cells have centrosomes.