Quiz: Cell Transport Mechanisms — 9 questions

1. What distinguishes passive transport from active transport in cell membrane processes?

A. Passive transport moves molecules down their concentration gradient without energy, while active transport requires energy to move molecules against the gradient.

B. Passive transport only involves water movement, whereas active transport involves all molecules.

C. Passive transport moves molecules against their concentration gradient, active transport moves down it.

D. Passive transport requires energy, while active transport does not.

Answer: (A)

Explanation

Passive transport moves molecules from high to low concentration without using energy, relying on the concentration gradient. Active transport, on the other hand, requires energy (ATP) to move molecules against their concentration gradient, from low to high concentration.

2. Which of the following best describes passive transport in cell membranes?

A. Transport molecules without energy expenditure down their concentration gradient

B. Transport molecules against their concentration gradient using ATP

C. Bulk transport through vesicles during endocytosis

D. Movement of water only through aquaporins

Answer: (A)

Explanation

Passive transport occurs without energy and moves molecules down their concentration gradient, unlike active transport which requires ATP. Vesicle-mediated bulk transport is a different process, and water movement via aquaporins is a specific type of passive transport called osmosis.

3. Which process involves the cell membrane engulfing material by folding inward?

A. Osmosis

B. Facilitated diffusion

C. Simple diffusion

D. Endocytosis

Answer: (D)

Explanation

Endocytosis is the process where the cell membrane folds inward to engulf external materials, forming a vesicle that brings substances into the cell. This is distinct from diffusion and osmosis, which are passive processes.

4. Which structure is primarily responsible for facilitating the movement of large, charged molecules across the cell membrane?

A. Channel proteins

B. Transport proteins

C. Vesicles

D. Water channels (aquaporins)

Answer: (B)

Explanation

Transport proteins are specialized for moving large or charged molecules across the membrane, whereas channel proteins form pores for specific ions or molecules, and aquaporins facilitate water movement.

5. How does a hypotonic solution affect animal and plant cells differently?

A. It causes animal cells to shrink and plant cells to burst.

B. It has no effect on either cell type.

C. It causes both animal and plant cells to shrink.

D. It causes animal cells to swell and potentially burst, while plant cells tolerate swelling due to their cell wall.

Answer: (D)

Explanation

In a hypotonic solution, water enters the cell. Animal cells may swell and burst (lysis) because they lack a rigid wall. Plant cells, however, have a cell wall that provides structural support, allowing them to swell without bursting, often resulting in turgor pressure.

6. According to the revision sheet, what role does ATP play in cell transport?

A. It provides energy for passive diffusion

B. It powers active transport to move molecules against their gradients

C. It assists in the formation of vesicles during endocytosis

D. It is required for osmosis

Answer: (B)

Explanation

ATP supplies the energy necessary for active transport, enabling cells to move molecules against their concentration gradients, unlike passive processes that do not require energy.

7. What is the key difference between osmosis and diffusion?

A. Osmosis involves water movement, diffusion involves solutes only

B. Osmosis requires energy, diffusion does not

C. Osmosis is active transport, diffusion is passive

D. Osmosis occurs only in plant cells, diffusion occurs in all cells

Answer: (A)

Explanation

Osmosis is the movement of water across a semi-permeable membrane, driven by solute concentration differences, while diffusion typically involves solutes moving down their gradient.

8. In the context of tonicity, what happens to animal cells placed in a hypertonic solution?

A. They swell and may burst

B. They shrink or shrivel

C. They remain unchanged

D. They actively absorb water

Answer: (B)

Explanation

In a hypertonic solution, water exits animal cells, causing them to shrink or shrivel, which can be damaging. Plant cells are more tolerant due to turgor pressure.

9. Which of these statements is true about the role of transport proteins?

A. They allow all molecules to pass through freely

B. They enable selective movement of specific molecules

C. They only function during active transport

D. They are only found in plant cells

Answer: (B)

Explanation

Transport proteins are crucial for selective permeability, allowing specific molecules to cross the membrane efficiently and selectively.