Question 1

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

Accepted Answer

Cholesterol increases membrane fluidity at high temperatures and decreases it at low temperatures.

Question 2

In the structure of a transmembrane protein, where are the hydrophobic amino acids most likely to be found?

Accepted Answer

Within the membrane-spanning regions interacting with the lipid tails.

Question 3

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

Accepted Answer

Oxygen (O$$_2)$$

Question 4

Facilitated diffusion differs from simple diffusion in that:

Accepted Answer

Facilitated diffusion requires membrane proteins, while simple diffusion does not.

Question 5

Which of the following best describes the movement of water during osmosis?

Accepted Answer

Water moves from an area of low solute concentration to an area of high solute concentration.

Question 6

What is the main function of the Na$$^+/K$^+$$ pump in animal cells?

Accepted Answer

To maintain a higher concentration of Na$$^+$$ outside the cell and K$$^+$$ inside the cell.

Question 7

Which side of the membrane becomes more positively charged as a result of the Na$$^+/K$^+$$ pump activity?

Accepted Answer

The extracellular side

Question 8

What is the direct energy source for the proton (H$$^+) $$pump shown in the diagram?

Accepted Answer

ATP hydrolysis

Question 9

Which of the following is true about active transport?

Accepted Answer

It moves molecules against their concentration gradient using energy.

Question 10

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

Accepted Answer

It will swell and may burst due to water influx.

Question 11

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

The cell uses specific receptors to internalize particular molecules from the extracellular fluid.

Question 12

Which of the following statements about membrane carbohydrates is correct?

Accepted Answer

They are found on the extracellular surface and play a role in cell recognition.

Question 13

Which process requires the use of vesicles to move large molecules out of the cell?

Accepted Answer

Exocytosis

Question 14

Which of the following best explains why plant cells do not burst in a hypotonic environment?

Accepted Answer

The cell wall provides structural support and prevents excessive water uptake.

Question 15

Which of the following is a correct statement about facilitated diffusion?

Accepted Answer

It requires a membrane protein but does not require energy.

Question 16

What is the main function of the large central vacuole in plant cells?

Accepted Answer

To store water and solutes and create internal pressure.

Question 17

Which of the following best describes pinocytosis?

Accepted Answer

The cell engulfs extracellular fluid and dissolved solutes in small vesicles.

Question 18

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

Accepted Answer

Storing genetic information.

Question 19

Which equation best represents the movement of water during osmosis?

Accepted Answer

$$\Delta \Psi = \Psi_s + \Psi_p$$

Question 20

A solution with a higher solute concentration than the cytoplasm of a cell is called:

Accepted Answer

Hypertonic

Cell Membrane Structure and Transport Mechanisms

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