Cell : The Unit of Life Descriptive Answer Biology Class-9 ICSE Selina Publishers

Cell : The Unit of Life Descriptive Answer Biology Class-9 ICSE Selina Publishers Solutions Chapter-2. Step By Step ICSE Selina Concise Solutions of Chapter-2 Cell : The Unit of Life with Exercise-2 including MCQs, Very Short Answer Type, Short Answer Type, Long Answer Type and Structured/Application Questions Solved . Visit official Website CISCE for detail information about ICSE Board Class-9.

Cell : The Unit of Life Exe-2 Descriptive Answer Biology Class-9 ICSE Concise Selina Publishers

Board ICSE
Publications Selina Publication
Subject Biology
Class 9th
Chapter-2 Cell : The Unit of Life
Book Name Concise
Topics Solution of D. Descriptive Answer Type
Academic Session 2023-2024

D. Descriptive Answer Type

Cell : The Unit of Life Class-9 Biology Concise Solutions  

Page 22

Question 1. 

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

Answer:

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. 

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

Answer:

(a) Protoplasm and cytoplasm
Protoplasm Cytoplasm
(i) It is the living matter, the total substance of a living cell, i.e. the cytoplasm and the nucleus. (ii) It is a mixture of water and soluble organic and inorganic compounds, in which various cell organelles are embedded.
(b) Nucleolus and nucleus

 

Nucleolus Nucleus
(i) It is a round-shaped nucleoli present inside the nucleus. (ii) It is a dense spherical structure present in the cell that contains a network of thread-like structures called chromatin fibres.
 
(c) Centrosome and chromosome

 

Centrosome  Chromosome
(i) It is a clear area of cytoplasm close to the nucleus, from which spindle fibres develop during cell division.

 

(ii) Centrosome is found only in an animal cell.

(i) Chromosomes carry hereditary information or genes which transmit genetic characters from parents to offspring.

 

(ii) Chromosomes are found in the nucleus of both, animal and plant cells.

 
(d) defference between Cell wall and cell membrane

 

Cell wall and Cell membrane
(i) It is a non-living rigid layer. (i) It is a living, thin, flexible membrane.
(ii) It is made of cellulose. (ii) It is made of lipoproteins.
(iii) It is freely permeable. (iii) It is semi-permeable.
 
(e) Plant cell and animal cell

 

Plant cell Animal cell
(i) Cell wall is present. (i) Cell wall is absent.
(ii) Centrosome is absent. (ii) Centrosome is present.
(iii) Vacuoles are large and prominent. (iii) Vacuoles are small and temporary.
(iv) Plastids are present. (iv) Plastids are absent.
 
(f) Prokaryotes and eukaryotes

 

Prokaryotes Eukaryotes
(i) Organisms with cells containing a primitive, undefined nucleus are called prokaryotes. (i) Organisms with cells containing a well-defined nucleus with a nuclear membrane are called eukaryotes.
(ii) They contain small ribosomes. (ii) They contain larger ribosomes.
(iii) They lack other cell organelles. (iii) They contain other cell organelles.
(iv) Examples: Bacteria, blue-green algae (iv) Examples: Euglena, Human beings

 

Question 3.

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

Answer:

(a) Plasma membrane:

(1) Separates contents of the cell from its surroundings

(2) Regulates the entry of certain solutes and ions

(3) Maintains the shape of animal cell

(b) Ribosome:

(1) Protein synthesis

(c) Lysosomes:

(1) Intracellular digestion 

(2) Destroy foreign substances

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

(d) Mitochondria:

(1) Synthesis of respiratory enzymes

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

(e) Golgi apparatus:

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

(2) Formation of acrosome of sperm

(f) Cytoplasm:

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

(2) All metabolic activities occur in it.

(g) Asters of centrosome:

(1) Initiates and regulates cell division

(2) Forms spindle fibres

(h) Chromosomes:

(1) Carry genetic characters from parents to offspring

(i) Glycogen granule:

(1) Serves as food for the cell

(j) Vacuoles:

(1) Gives turgidity to the cells

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

Question 4.

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

Answer:

Living cell Brick in a wall
1. Non-rigid living structure 1. Rigid non-living structure
2. Mainly composed of cellulose 2. Mainly composed of soil
3. Freely permeable 3. Impermeable

 

Question 5.

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

Answer:

Common features found in both plant and animal cells:

(1) Presence of cell membrane

(2) Presence of liquid matrix called cytoplasm in the cell

(3) Presence of mitochondria which produces energy

(4) Presence of ribosomes that synthesize proteins

(5) Presence of Golgi body

(6) Presence of a prominent nucleus

—  : End of Cell : Unit of Life D. Descriptive Answer Class-9 ICSE Biology Solutions :–

Return to  Return to Concise Selina ICSE Biology Class-9 

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