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

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

Accepted Answer

The cell will shrink because water moves out of the cell by osmosis.

Question 3

Which of the following molecules would most easily cross the plasma membrane without the help of a transport protein?

Accepted Answer

Oxygen ($$\mathrm{O_2$})$$

Question 4

Which statement correctly compares saturated and unsaturated fatty acids in membrane phospholipids?

Accepted Answer

Unsaturated fatty acids have one or more double bonds, causing kinks that increase membrane fluidity.

Question 5

Facilitated diffusion differs from simple diffusion in that:

Accepted Answer

Facilitated diffusion requires membrane proteins to transport molecules across the membrane.

Question 6

Which of the following best explains why phospholipids form bilayers in water?

Accepted Answer

Their hydrophilic heads interact with water while hydrophobic tails avoid water.

Question 7

A patient is given an intravenous solution that is hypotonic compared to their blood plasma. What is the most likely effect on their red blood cells?

Accepted Answer

The cells will swell and may burst due to water entering by osmosis.

Question 8

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

Accepted Answer

Synthesizing proteins for the cell.

Question 9

Which process is illustrated by the movement of water across a membrane from an area of low solute concentration to high solute concentration?

Accepted Answer

Osmosis

Question 10

A cell uses energy to move sodium ions ($$\mathrm{Na^+}) $$from a low concentration inside the cell to a high concentration outside the cell. Which transport mechanism is being used?

Accepted Answer

Active transport

Question 11

Which of the following factors would increase the fluidity of a cell membrane?

Accepted Answer

A higher proportion of unsaturated fatty acids in phospholipids.

Question 12

Which of the following statements about passive transport is correct?

Accepted Answer

It moves substances down their concentration gradient without using cellular energy.

Question 13

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

Accepted Answer

Amphipathic nature (having both hydrophilic and hydrophobic regions)

Question 14

A mutation causes a cell to produce phospholipids with only saturated fatty acid tails. What effect would this have on the cell membrane?

Accepted Answer

The membrane would become less fluid and more rigid.

Question 15

Which of the following best describes the movement of glucose into a cell via a channel protein?

Accepted Answer

Facilitated diffusion

Question 16

If a cell membrane is composed of phospholipids with mostly unsaturated fatty acid tails, what would be the expected effect on the membrane at low temperatures?

Accepted Answer

The membrane would remain more fluid than one with saturated fatty acids.

Question 17

Which of the following is a major function of membrane proteins?

Accepted Answer

Transporting specific molecules across the membrane

Question 18

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the movement of water across a selectively permeable membrane from low solute concentration to high solute concentration.

Question 19

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

Accepted Answer

There will be no net movement of water; the cell will remain the same size.

Question 20

Which of the following best explains why ions such as $$\mathrm{Na^+}$$ and $$\mathrm{K^+}$$ cannot easily cross the plasma membrane?

Accepted Answer

They are charged and cannot pass through the hydrophobic core of the membrane.

Plasma Membrane Structure and Function: Lipids, Transport, and Membrane Dynamics

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