Question 1

Which statement best describes the selective permeability of the plasma membrane?

Accepted Answer

It allows some substances to cross more easily than others, depending on their chemical properties.

Question 2

According to the fluid mosaic model proposed by Singer and Nicolson, which of the following is TRUE about the structure of the plasma membrane?

Accepted Answer

Proteins are dispersed throughout a fluid bilayer of phospholipids, allowing lateral movement.

Question 3

Which equation best represents the spontaneous nature of diffusion across a membrane?

Accepted Answer

$$\Delta G \u003c 0$$

Question 4

A red blood cell is placed in a hypotonic solution. What will happen to the cell, and why?

Accepted Answer

It will swell and may burst because water will move into the cell by osmosis.

Question 5

Which of the following molecules would pass most rapidly through the plasma membrane by simple diffusion?

Accepted Answer

Carbon dioxide ($$\mathrm{CO_2$})$$

Question 6

Which process requires the expenditure of energy ($$\Delta G \u003e 0) to $$move molecules across the plasma membrane?

Accepted Answer

Active transport

Question 7

A cell uses a sodium-potassium pump to maintain ion gradients. Which best describes this process?

Accepted Answer

It requires ATP to move sodium and potassium ions against their concentration gradients.

Question 8

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

Accepted Answer

Providing structural support to the cell wall

Question 9

Which type of endocytosis involves the engulfment of solid particles by the cell?

Accepted Answer

Phagocytosis

Question 10

A cell is placed in an isotonic solution. What will happen to the cell?

Accepted Answer

It will remain unchanged because there is no net movement of water.

Question 11

Which of the following statements about facilitated diffusion is TRUE?

Accepted Answer

It uses specific transport proteins to move polar molecules and ions down their concentration gradients.

Question 12

Which property of phospholipids is most important for the formation of the plasma membrane?

Accepted Answer

Their amphipathic nature, having both hydrophilic and hydrophobic regions.

Question 13

Which of the following best explains why hydrophobic substances pass through membranes more rapidly than hydrophilic substances?

Accepted Answer

Hydrophobic substances dissolve in the lipid bilayer, allowing them to diffuse easily.

Question 14

Which of the following is a function of carbohydrates attached to the plasma membrane?

Accepted Answer

Cell-cell recognition

Question 15

In a plant cell placed in a hypertonic solution, what is the most likely outcome?

Accepted Answer

The cell will lose water and undergo plasmolysis.

Question 16

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

The cell imports specific macromolecules in response to binding of ligands to surface receptors.

Question 17

Which of the following is TRUE about dynamic equilibrium in diffusion?

Accepted Answer

There is no net movement of molecules, but individual molecules continue to move.

Question 18

Which of the following is NOT a mode of transport across biological membranes?

Accepted Answer

Photosynthesis

Question 19

Which of the following best describes the role of transport proteins in the plasma membrane?

Accepted Answer

They are specific for the solutes they transport and help move polar molecules and ions.

Question 20

A cell is actively importing macromolecules by forming vesicles from the plasma membrane. Which process is this?

Accepted Answer

Endocytosis

Lecture 7 - Plasma Membranes and Transport Mechanisms

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