Cell Biology and Transport Practice Quiz (17 questions)

1. Which structure is the site of protein synthesis in a cell?

A. The cell membrane.

B. Ribosomes.

C. Mitochondria.

D. The nucleus.

Answer: (B)

Explanation

Ribosomes are the structures where proteins are synthesised. Mitochondria release energy through respiration, while the nucleus contains DNA.

2. Which comparison correctly distinguishes how light and electron microscopes work and the samples they can examine?

A. A light microscope uses light and can view living samples, while an electron microscope uses electrons and cannot view living samples.

B. A light microscope uses electrons and can view living samples, while an electron microscope uses light and cannot view living samples.

C. Both microscopes use electrons, but only a light microscope can view living samples.

D. Both microscopes use light, but only an electron microscope can view living samples.

Answer: (A)

Explanation

A light microscope uses light and can be used to view living samples; an electron microscope uses an electron beam and cannot view living samples. A common mix-up reverses which microscope can examine living material.

3. A scientist observes a small, single-celled organism with one loop of DNA and several small DNA rings. What are the small rings called?

A. Nuclei, which contain the organism's DNA.

B. Chromosomes, which hold the main genetic material.

C. Mitochondria, which contain DNA for respiration.

D. Plasmids, which are additional DNA rings.

Answer: (D)

Explanation

Bacteria contain a single loop of DNA as their main genetic material, along with small additional DNA rings called plasmids. Chromosomes are not the name for these additional rings.

4. A cell takes up a substance from an area where its concentration is lower than inside the cell. What makes this movement active transport?

A. Water moves across a partially permeable membrane toward a more concentrated solution.

B. The substance spreads through the cell membrane as concentrations become more equal.

C. The substance moves down its concentration gradient without requiring energy.

D. The substance moves against its concentration gradient using energy released by respiration.

Answer: (D)

Explanation

Active transport moves particles from lower to higher concentration, against the concentration gradient, using energy released by respiration. Diffusion is a plausible alternative, but it moves particles down their concentration gradient.

5. A nerve cell needs to transmit electrical impulses rapidly along its axon. Which adaptation directly helps increase transmission speed?

A. A myelin sheath that insulates the axon.

B. A long projection that absorbs water from soil.

C. A haemoglobin-rich interior that binds oxygen.

D. Many mitochondria that release energy for contraction.

Answer: (A)

Explanation

The myelin sheath insulates a nerve cell's axon and increases the speed of impulse transmission. Many mitochondria are an adaptation of muscle cells for energy release during contraction.

6. How does the timing of cell differentiation generally differ between animals and plants?

A. Plant cells differentiate before development, while animal cells differentiate after maturity.

B. Most animal cells differentiate early, while plant cells differentiate throughout the plant's lifetime.

C. Most plant cells differentiate early, while animal cells differentiate throughout their lifetime.

D. Animal and plant cells generally differentiate at the same stage of development.

Answer: (B)

Explanation

Most animal cells differentiate early in development, whereas plant cells differentiate throughout the plant's lifetime. The reverse pattern is a plausible confusion, but it contradicts this distinction.

7. A process moves substances across a membrane without energy from respiration. Which classification correctly distinguishes this process from active transport?

A. It is active, like diffusion; osmosis requires respiratory energy.

B. It is passive, like diffusion or osmosis; active transport requires respiratory energy.

C. It is active, like osmosis; diffusion and active transport both require respiratory energy.

D. It is passive, like active transport; diffusion requires respiratory energy.

Answer: (B)

Explanation

Diffusion and osmosis are passive processes that do not require energy, whereas active transport requires energy released by respiration. A key misconception is treating diffusion as energy-dependent, even though it is passive.

8. A partially permeable membrane separates a dilute solution from a concentrated solution. Which movement describes osmosis?

A. Water diffuses from the dilute solution to the concentrated solution through the membrane.

B. Solute particles diffuse from the concentrated solution to the dilute solution through the membrane.

C. Water moves from the concentrated solution to the dilute solution through the membrane.

D. Water and solute particles move equally in both directions through the membrane.

Answer: (A)

Explanation

Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane. Solute movement alone is not osmosis, which specifically concerns water.

9. An image is magnified $120\times$ and measures $6\,\text{mm}$. What is the specimen’s actual size?

A. $20\,\text{mm}$

B. $0.05\,\text{mm}$

C. $0.2\,\text{mm}$

D. $720\,\text{mm}$

Answer: (B)

Explanation

Rearranging magnification equals image size divided by actual size gives actual size as image size divided by magnification: $6\div120=0.05\,\text{mm}$. Multiplying image size by magnification incorrectly reverses the relationship.

10. Which feature distinguishes eukaryotic animal and plant cells from prokaryotic bacteria?

A. They contain plasmids as their main genetic material.

B. Their DNA is organised into chromosomes inside a nucleus.

C. They are smaller and consist of a single cell.

D. Their DNA is arranged in a loop within the cytoplasm.

Answer: (B)

Explanation

Animal and plant cells are eukaryotic, with DNA organised into chromosomes inside a nucleus, while bacteria lack a nucleus. A bacterial DNA loop is a real feature, but it does not distinguish eukaryotes from prokaryotes.

11. Why does the flat, biconcave shape of a red blood cell help it perform its function?

A. It creates branched connections for transmitting impulses.

B. It provides contractile fibres for movement of the body.

C. It increases the surface-area-to-volume ratio for oxygen transport.

D. It increases surface area for absorbing mineral ions from soil.

Answer: (C)

Explanation

The biconcave disc shape increases a red blood cell's surface-area-to-volume ratio, supporting its role in oxygen transport. Contractile fibres are associated with muscle cells, not red blood cells.

12. Which adaptation helps a sperm cell swim toward an ovum?

A. A biconcave shape and haemoglobin for oxygen transport.

B. A long projection and active transport of mineral ions.

C. Branched dendrites and a myelin sheath for impulses.

D. A tail for movement and many mitochondria to release energy.

Answer: (D)

Explanation

A sperm cell has a tail for swimming and many mitochondria that release the energy needed for movement. A biconcave shape and haemoglobin are adaptations of red blood cells for oxygen transport.

13. Which description defines diffusion?

A. The movement of water through a partially permeable membrane toward a dilute solution

B. The net movement of particles from higher to lower concentration without energy from respiration

C. The movement of particles from higher to lower concentration powered by respiration

D. The net movement of particles from lower to higher concentration using energy from respiration

Answer: (B)

Explanation

Diffusion is the net movement of particles down a concentration gradient, from higher to lower concentration, without energy from respiration. Movement against the gradient is associated with active transport, not diffusion.

14. What is the main role of the cell membrane?

A. Containing the cell's DNA within a nucleus.

B. Releasing energy through the process of respiration.

C. Providing a site where proteins are synthesised.

D. Controlling the movement of substances into and out of the cell.

Answer: (D)

Explanation

The cell membrane controls the movement of substances into and out of a cell. Ribosomes, rather than the membrane, are the site of protein synthesis.

15. A plant cell needs to absorb light energy for photosynthesis. Which structure performs this role?

A. The permanent vacuole containing cell sap.

B. Chloroplasts containing chlorophyll.

C. The cellulose cell wall surrounding the cell.

D. Mitochondria releasing energy through respiration.

Answer: (B)

Explanation

Chloroplasts contain chlorophyll, which absorbs light energy for photosynthesis. The cellulose cell wall strengthens the plant cell but does not absorb light for photosynthesis.

16. A specimen has an actual size of $0.02\,\text{mm}$ and an image size of $8\,\text{mm}$. What is its magnification?

A. $160\times$

B. $400\times$

C. $0.0025\times$

D. $40\times$

Answer: (B)

Explanation

Magnification is image size divided by actual size, so $8\div0.02=400$. Dividing actual size by image size reverses the formula and gives a value that is not the magnification.

17. Which structure can an electron microscope reveal that is too small to be seen with a light microscope?

A. A ribosome within a cell

B. A large vacuole within a plant cell

C. A whole cell within a tissue

D. A leaf visible to the naked eye

Answer: (A)

Explanation

Electron microscopes can reveal sub-cellular structures such as ribosomes that are too small to be seen with a light microscope. A whole cell or large vacuole does not illustrate this particular advantage.