Cell: The Unit of Life Chapter-Wise Test 9

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which statement correctly describes the genomic DNA of a typical prokaryotic cell?

It consists of several linear chromosomes enclosed by a nuclear membrane.
It is generally a single circular DNA molecule that is not enclosed by a nuclear membrane.
It occurs only as small circular plasmids dispersed throughout the cytoplasm.
It is enclosed within a double-membrane-bound nucleoid.
2

A prokaryotic cell lacks a well-defined nucleus. Its genomic DNA is generally a single circular chromosome that remains naked because it is not enclosed by a nuclear membrane. Plasmids, when present, occur in addition to the genomic DNA.

What is a major structural function of the bacterial cell wall?

It synthesises proteins required for bacterial growth.
It encloses the genetic material within the nucleoid.
It produces ATP by active transport.
It determines cell shape and prevents the bacterium from bursting or collapsing.
4

The bacterial cell wall determines the shape of the cell and provides strong structural support. This support protects the bacterium from bursting or collapsing.

Which description correctly identifies bacterial pili?

Elongated tubular surface structures made of a special protein
Small membrane-bound vesicles containing reserve materials
Infoldings of the plasma membrane containing respiratory enzymes
Long locomotory structures composed of an axoneme
1

Pili are elongated tubular surface structures made of a special protein. Pili and fimbriae are bacterial surface structures, but they do not function as locomotory flagella.

How are food vacuoles formed in many protistan cells?

By the division of mitochondria
By fusion of nuclear pores
By engulfing food particles
By the stacking of thylakoids
3

Food vacuoles in many cells, including protists, are formed when the cell engulfs food particles. They differ functionally from the contractile vacuole, which is involved in osmoregulation and excretion.

Lysosomal vesicles are formed through the packaging activity of which organelle?

Smooth endoplasmic reticulum
Golgi apparatus
Mitochondrion
Centrosome
2

Lysosomes are membrane-bound vesicular structures formed through packaging by the Golgi apparatus. They contain hydrolytic enzymes capable of digesting several types of biological macromolecules.

Which option gives the typical shape and dimensions of a mitochondrion?

Spherical, about 5–10 µm in diameter
Disc-shaped, about 2–4 µm wide and 10–20 µm long
Thread-like, about 15 nm wide and 20 nm long
Sausage-shaped or cylindrical, about 0.2–1.0 µm in diameter and 1.0–4.1 µm long
4

A mitochondrion is typically sausage-shaped or cylindrical. Its diameter is approximately 0.2–1.0 µm, with an average of about 0.5 µm, and its length is approximately 1.0–4.1 µm.

Which statement correctly compares the two membranes surrounding a chloroplast?

The inner chloroplast membrane is relatively less permeable.
The outer chloroplast membrane forms thylakoid stacks.
The inner chloroplast membrane contains the 9+2 microtubule array.
Both chloroplast membranes are replaced by the tonoplast in mature cells.
1

A chloroplast is surrounded by two membranes, of which the inner membrane is relatively less permeable. The space enclosed by the inner membrane is called the stroma.

What is the lumen of a chloroplast thylakoid?

The space between the two chloroplast-envelope membranes
The fluid matrix surrounding all chloroplast structures
The space enclosed by the thylakoid membrane
The region containing chloroplast DNA and ribosomes
3

The thylakoid membrane encloses an internal space called the lumen. Thylakoids are flattened membranous sacs present within the chloroplast stroma.

Which chloroplast regions are correctly matched with their principal photosynthetic reactions?

Grana — dark reactions; stroma — light reactions
Outer membrane — light reactions; inner membrane — dark reactions
Lumen — dark reactions; stroma lamellae — carbohydrate storage
Grana — light reactions; stroma — dark reactions
4

Grana are the sites of the light reactions of photosynthesis, whereas the chloroplast stroma is the site of the dark reactions. Chlorophyll pigments are located in the thylakoids that form the grana.

Which combination correctly states the functions of centrioles in animal cells?

Formation of lysosomes and modification of proteins
Formation of basal bodies and spindle fibres of the spindle apparatus
Synthesis of lipids and steroidal hormones
Formation of chromatin and nuclear pores
2

Centrioles form the basal bodies of cilia and flagella. In animal cells, they also form spindle fibres that give rise to the spindle apparatus during cell division.

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