Selina Concise Class 9 Biology Chapter 2 Cell: The Unit of Life Solution

Selina Concise Class 9 Biology Solution Chapter No. 2- ‘Cell: The Unit of Life’ For ICSE Board Students.

Exercise Solution

A.)

1.)

Answer: (a) Ribosome- Synthesis of proteins

The ribosomes are sites of protein synthesis or also known as factories for the synthesis of proteins.

2.)

Answer: (b) A single cell

The life of the mango and frog were started as a seed or fertilized egg in the beginning. The egg is single cell which is produced by mother frog.

3.)

Answer: (d) Cell membrane

Both plant cell and animal cell contains cell membrane. So, the mango plant and organism like money will have cell membrane.

4.)

Answer: (a) Absence of centrosome

The centrosome is mainly present in the animal cell and absent in the plant cell.

5.)

Answer: (c) Cellulose

The plant cell wall is surrounded by cell membrane and it is made up of non-living substance known as cellulose.

6.)

Answer: (a) Mitochondria

In the cells, mitochondria releases energy and cell respiration takes place here. So the Mitochondria is correct answer.

B.)

1.)

a) Mitochondria

b) Ribosomes

c) Chromosomes

d) Centrosome

e) Lysosome

f) Plasma or cell membrane

2.)

a) False

b) False

c) True

d)True

e) False

f) True

g) True

3.)

Answer:

The chromosomes contains genetic characters from the parents to offspring. The chromosomal number is definite in each species. The human cell has 23 pairs (in total 46) of chromosomes.

4.)

Answer:

The DNA or Deoxyribonucleic acid is the chemical substance that constitutes the genes or gene are made up of DNA which is a chemical substance.

5.)

Column A Column B (Answers)
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.)

a) Lysosomes

b) Centriole

c) Plasma membrane

d) Insects

e) Genes

f) Leucoplast

C.)

1.)

Answer:

The Protoplasm term means the living substances in an organism and its chemical composition is very complex. The chemical elements that takes part in the composition of protoplasm are hydrogen, oxygen, carbon, sulphur, nitrogen, phosphorus and iron. It ceases to be protoplasm that’s why protoplasm cannot be analysed chemically.

2.)

Answer:

Organ Organelle
It is has organ system It has single cell
These have macroscopic structure These have microscopic structure
It is part of the body It is part of cell
It is present in multicellular organism It is present in unicellular organism

3.)

Answer:

No, the cell of an elephant is not larger than cell of rat. In fact, cell of elephant and cell of rat are of same size. Cell size does not vary within the organisms but the number of cell can vary. An elephant has more number of cells than rat. So, an elephant cell is not large when compared to rat.

4.)

a)

Protoplasm Cytoplasm
The protoplasm have nucleus and it is collection of cytoplasm, nucleus and cell membrane. The cytoplasm does not have nucleus and it is fluid part of protoplasm.

b)

Nucleolus Nucleus
It is sub-organelle in the nucleus It is large organelle found in eukaryotic cell.

c)

Centrosome  Chromosome
It is made up of microtubules, cenexin, tektin, centrin and present is only metazoans. It is made up of centric heterochromatin and present in all eukaryotes.

d)

Cell wall Cell membrane
It is absent in animal cells and can be observed under light microscope. It is present in all living cells and can be observed in electron microscope.

e)

Plant cell Animal cell
Chloroplast is present in the plant cell. Chloroplast is absent in animal cell.

f)

Prokaryotes Eukaryotes
The prokaryotes have no true nucleus and no nuclear membrane. The eukaryotes have true nucleus with nuclear membrane.

5.)

Answer:

The features that only found in plant cell are presence of cell wall, presence of plastids and presence of large vacuoles.

The centrosome found in only animal cell.

6.)

Answer:

The cells are small in their size. They enable different areas of the cell and this is for the communication with each other. The cell will function effectively by this way. The size is smaller in order to have larger surface are is to volume ratio because of this more substance will undergo diffusion in and out of the cell. That’s why cells generally small in size.

D.)

1.)

Answer:

The following are features or postulates of cell theory:

The cell

– Is the smallest unit of structure of all living thing.

– Is the unit of function of all living thing.

– Are arise from pre-existing cells.

In the year 1839, the cell theory was proposed by Theodor Schwann and Matthias Schleiden. It was later modified by Rudolf Virchow and says all cells arise from pre-existing cells in the year 1858.

2.)

Answer:

Living cell Brick
It is living cell It is non-living cell
For the proper functioning, it requires continuous source of energy. Bricks don’t need energy
It is freely permeable and composed of cellulose. It is impermeable and composed of soil

3.)

Question Plastid Pigment
a) Chromoplasts Xanthophyll
b) Chromoplasts Carotene
c) Chloroplasts Chlorophyll
d) Leucoplasts No pigment

4.)

a)

Functions: The plasma membrane separates contents from its surrounding. It helps to maintain animal cell shape. It is responsible for the regulation of entry of ions and solutes.

b)

Function: Protein synthesis.

c)

Function: It destroy foreign substances. Includes intracellular digestion.

d)

Functions: The cell respiration takes place to release energy. It is also known as ‘Power house of the cell’.

e)

Functions:Formation of acrosome of sperm. Cell secretions of enzymes and hormones.

f)

Functions: All metabolic activities takes place here. Cytoplasm includes organelles that perform various functions.

g)

Function: Centrosome develops spindle fibres. Play role during cell division.

h)

Functions:From parents to offspring, chromosome carry the genetic feature.

i)

Functions: Glycogen food material for the cells.

j)

Functions: It stores various material like water, food and waste products.

5.)

Answer:

Six features that are observed both in plant and animal cells:

  • Mitochondria found in the cells.
  • Presence of cell membrane
  • Presence of Golgi body
  • Presence of cytoplasm
  • Presence of ribosomes
  • Protein synthesis by ribosome
  • Presence of prominent nucleus

E.)

1.)

a)

In the figure B, there is presence of definite cell wall observed, large vacuoles are observed and Cytoplasm is not so dense. Therefore, the figure B is of Plant cell.

b)

The common structure in both the cells are:

Cytoplasm

Nucleus

Cell membrane

Mitochondria

Ribosomes

Golgi bodies

c)

Plant cell-

Have cell wall and contain plastids

Large vacuole

Animal cell-

Presence of centrosome

Denser cytoplasm

Updated: August 20, 2021 — 12:58 pm

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