NCERT Class 11-Biology: Chapter –8 the Unit of Life Part 2

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Question 10:

Which of the following is not true of a eukaryotic cell?

a. It has 80S type of ribosome present in the mitochondria

b. It has 80S type of ribosome present in the cytoplasm

c. Mitochondria contain circular DNA

d. Membrane bound organelles are present

Answer: (a)

Question 11:

Which of the following statements is not true for plasma membrane?

a. It is present in both plant and animal cell

b. Lipid is present as a bilayer in it

c. Proteins are present integrated as well as loosely associated with the lipid bilayer

d. Carbohydrate is never found in it

Answer: (d)

Question 12:

Plastid differs from mitochondria on the basis of one of the following features. Mark the right answer.

a. Presence of two layers of membrane

b. Presence of ribosome

c. Presence of chlorophyll

d. Presence of DNA

Answer: (c)

Question 13:

Which of the following is not a function of cytoskeleton in a cell?

a. Intracellular transport

b. Maintenance of cell shape and structure

c. Support of the organelle

d. Cell motility

Answer: (a)

Question 14:

The stain used to visualise motochondria is

a. Fast green

b. Safranin

c. Aceto carmne

d. Janus green

Answer: (d)

Very Short Answer Type Questions

Question 1:

What is the significance of vacuole in a plant cell?


Vacuole is a membrane-bound space found in the cytoplasm. It is found in both plant and animal cells but it is much larger in plants (occupies 90% of the space in plant cells).

Vacuole in a plant cell helps in

  • The storage

  • Waste disposal

  • Cell elongation

  • Cell protection

Question 2:

What does ‘S’ refer in a & a ribosome?


Ribosomes are the site of protein synthesis. The ‘S’ refers to Svedberg’s unit or sedimentation coefficient. It is indirectly a measure of density and size. In cells heavier the structure, higher is the sedimentation coefficient.

Question 3:

Mention a single membrane bound organelle which is rich in hydrolytic enzymes.


Lysosomes are the single membrane bound organelle which is rich in hydrolytic enzymes. They are formed by Golgi apparatus. The isolated lysosomal vesicles have been found to be very rich in almost all types of hydrolytic enzymes (hydrolases – lipases, proteases, carbohydrases) optimally active at the acidic pH.

Question 4:

What are gas vacuoles? State their functions?


Gas vacuoles are aggregates of hollow cylindrical structures called gas vesicles. They are found in blue-green and purple and green photosynthetic bacteria.

Functions of gas vacuoles are storing metabolic gases and take part in buoyancy.

Question 5:

What is the function of a polysome?


Several ribososmes attached to a single mRNA form a chain is called polysome. It is also called polyribosome.

The function of a polysome is to translate an mRNA into proteins.