Question 1

Which of the following best explains why winter wheat maintains membrane fluidity at low temperatures?

Accepted Answer

It increases the proportion of unsaturated fatty acids, preventing the membrane from solidifying.

Question 2

A scientist observes that a cell is able to import glucose even when the extracellular glucose concentration is lower than inside the cell. Which transport mechanism is most likely responsible?

Accepted Answer

Active transport using a carrier protein and ATP

Question 3

Which of the following statements about the sodium–potassium pump is CORRECT?

Accepted Answer

It exports 3 Na⁺ ions and imports 2 K⁺ ions against their gradients, using ATP.

Question 4

Which process is described by the following steps: ligand binding to a specific receptor, recruitment of coat proteins, and vesicle formation?

Accepted Answer

Receptor-mediated endocytosis

Question 5

A plant cell placed in a hypertonic solution will most likely undergo which process?

Accepted Answer

Plasmolysis

Question 6

Which of the following best describes the role of cholesterol in the plasma membrane at moderate temperatures?

Accepted Answer

It decreases membrane fluidity by restricting phospholipid movement.

Question 7

Which of the following is TRUE regarding integral and peripheral membrane proteins?

Accepted Answer

Integral proteins penetrate the hydrophobic core, while peripheral proteins are attached to the membrane surface.

Question 8

A cell uses a proton pump to create a high concentration of H⁺ outside the cell. Sucrose is then transported into the cell along with H⁺, without direct ATP use. This is an example of:

Accepted Answer

Co-transport (symport)

Question 9

Which of the following molecules can most easily cross the plasma membrane by simple diffusion?

Accepted Answer

O₂

Question 10

Which process is responsible for the rapid release of insulin from pancreatic β-cells into the bloodstream?

Accepted Answer

Bulk exocytosis

Question 11

A macrophage engulfs a bacterium by extending pseudopodia around it, forming a vesicle that later fuses with lysosomes. This process is best described as:

Accepted Answer

Phagocytosis

Question 12

Which of the following best explains why animal cells prefer isotonic environments?

Accepted Answer

To prevent net water gain or loss, maintaining cell volume

Question 13

Which of the following is a key difference between phagocytosis and pinocytosis?

Accepted Answer

Phagocytosis engulfs large particles, while pinocytosis internalizes extracellular fluid and dissolved solutes.

Question 14

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules down their concentration gradient through a protein channel or carrier, without energy input

Question 15

A cell is placed in a solution and water rushes into the cell, causing it to swell and become firm. What is the tonicity of the solution relative to the cell?

Accepted Answer

Hypotonic

Question 16

Which of the following is NOT a function of integral membrane proteins?

Accepted Answer

Anchoring the cytoskeleton to the membrane surface

Question 17

Which of the following best describes the energy requirements for receptor-mediated endocytosis?

Accepted Answer

ATP is required for coat protein assembly and vesicle formation.

Question 18

Which of the following scenarios illustrates co-transport in a plant cell?

Accepted Answer

Sucrose is transported into the cell along with H⁺ ions, using the H⁺ gradient established by a proton pump.

Question 19

Which of the following is a correct sequence of events for bulk exocytosis?

Accepted Answer

Synthesis & packaging → Vesicle targeting → Docking & fusion → Release

Question 20

Which of the following best explains why O₂ and CO₂ can cross the plasma membrane by simple diffusion, but Na⁺ cannot?

Accepted Answer

O₂ and CO₂ are small and non-polar, while Na⁺ is charged and hydrophilic.

Membrane Transport: Structure, Mechanisms, and Cellular Communication

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