Cell: The Unit of Life Chapter-Wise Test 6

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which of the following is identified as the largest isolated single cell?

A human nerve cell
A human red blood cell
The egg of an ostrich
A mesophyll cell
3

The egg of an ostrich is the largest isolated single cell. Nerve cells are among the longest cells, while human red blood cells are approximately 7.0 µm in diameter.

Which option correctly gives the approximate composition of the plasma membrane of a human erythrocyte?

40 per cent protein and 52 per cent lipid
52 per cent protein and 40 per cent lipid
52 per cent carbohydrate and 40 per cent protein
40 per cent carbohydrate and 52 per cent lipid
2

The membrane of a human erythrocyte contains approximately 52 per cent protein and 40 per cent lipid. The protein-to-lipid ratio varies considerably among different cell types.

Why do polar molecules generally require carrier proteins to cross the plasma membrane?

They are too small to enter the membrane.
They can move only against their concentration gradient.
They are repelled by the polar heads of phospholipids.
They cannot pass readily through the non-polar lipid bilayer.
4

Polar molecules cannot pass readily through the non-polar interior of the lipid bilayer. They therefore require membrane carrier proteins to facilitate their movement across the plasma membrane.

What is the principal role of plasmodesmata in plant tissues?

They connect the cytoplasm of neighbouring cells.
They attach chromosomes to spindle fibres.
They connect the thylakoids of different grana.
They join the inner and outer mitochondrial membranes.
1

Plasmodesmata traverse the cell walls and middle lamellae of neighbouring plant cells. They establish connections between the cytoplasm of adjacent cells.

The Golgi apparatus is an important site for the formation of which substances?

Cellulose and calcium pectate
Glycoproteins and glycolipids
DNA and histone proteins
ATP and ribosomal RNA
2

The Golgi apparatus modifies materials received from the endoplasmic reticulum and is an important site for the formation of glycoproteins and glycolipids.

Approximately how much of the volume of a plant cell may be occupied by vacuoles?

Up to 10 per cent
Up to 50 per cent
Up to 90 per cent
Exactly 100 per cent
3

Vacuoles may occupy up to 90 per cent of the volume of a plant cell. A vacuole is a membrane-bound cytoplasmic space enclosed by the tonoplast.

Which statement correctly compares the number of chloroplasts in Chlamydomonas and a mesophyll cell?

Both normally contain one chloroplast per cell.
Chlamydomonas contains 20–40 chloroplasts, whereas a mesophyll cell contains one.
Both normally contain 20–40 chloroplasts per cell.
Chlamydomonas may contain one chloroplast, whereas a mesophyll cell may contain 20–40.
4

The number of chloroplasts varies among cells. Chlamydomonas may have one chloroplast per cell, whereas a mesophyll cell may contain approximately 20–40 chloroplasts.

Which statement correctly distinguishes cilia from flagella?

Cilia are relatively short and may move the cell or surrounding fluid, whereas flagella are longer and are responsible for cell movement.
Cilia contain microtubules, whereas flagella contain only microfilaments.
Cilia are not covered by the plasma membrane, whereas flagella are membrane-bound.
Cilia occur only in prokaryotes, whereas flagella occur only in eukaryotes.
1

Cilia are comparatively short and work like oars, moving either the cell or the surrounding fluid. Flagella are longer and are mainly responsible for movement of the cell.

What is the perinuclear space?

The space enclosed within the nucleolus
The 10–50 nm space between the two membranes of the nuclear envelope
The space between the nucleus and the endoplasmic reticulum
The space occupied by chromatin during cell division
2

The nuclear envelope consists of two parallel membranes separated by a space of approximately 10–50 nm. This intervening region is called the perinuclear space.

Which statement correctly describes the relationship between the centromere and kinetochores?

The kinetochore joins two chromosomes, while the centromere forms the satellite.
The centromere occurs only in interphase, whereas kinetochores occur in the nucleolus.
The centromere is the primary constriction that holds two chromatids, and kinetochores occur on its sides.
The centromere is a secondary constriction formed between two kinetochores.
3

The centromere is the primary constriction of a chromosome and holds its two chromatids together. Disc-shaped structures called kinetochores are present on the sides of the centromere.

Performance Summary

Score:

Category Details
Total Attempts:
Total Skipped:
Total Wrong Answers:
Total Correct Answers:
Time Taken:
Average Time Taken per Question:
Accuracy:
0