Question 1

Which of the following best describes the process of diffusion across a selectively permeable membrane?

Accepted Answer

Movement of solutes from high concentration to low concentration, without the need for energy input.

Question 2

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

Accepted Answer

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

Question 3

Which equation correctly represents the relationship between solute concentration and water potential in osmosis?

Accepted Answer

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

Question 4

Which of the following statements about the fluid mosaic model of membranes is correct?

Accepted Answer

Phospholipids and proteins can move laterally within the layer, giving the membrane fluidity.

Question 5

A cell uses the sodium-potassium pump (Na+/K+ ATPase) to maintain ion gradients. Which of the following best describes the action of this pump?

Accepted Answer

It moves 3 Na+ ions out of the cell and 2 K+ ions in, using ATP.

Question 6

Which of the following best explains why ions such as Na+ and K+ cannot easily cross the lipid bilayer without assistance?

Accepted Answer

They are hydrophilic and charged, so they are repelled by the hydrophobic core of the bilayer.

Question 7

Which of the following is an example of secondary active transport?

Accepted Answer

The movement of glucose into a cell via a Na+/glucose symporter, using the Na+ gradient established by the Na+/K+ pump.

Question 8

A researcher adds a molecule that blocks all ATP production in a cell. Which of the following transport processes would be most directly affected?

Accepted Answer

Primary active transport of Na+ and K+.

Question 9

Which of the following best describes the difference between channel proteins and carrier proteins in membranes?

Accepted Answer

Channel proteins form open pores for specific molecules or ions, while carrier proteins undergo conformational changes to transport substances.

Question 10

Which of the following scenarios best illustrates the concept of an electrochemical gradient?

Accepted Answer

A difference in Na+ concentration and charge across a neuron's plasma membrane.

Question 11

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the movement of water from areas of low solute concentration to areas of high solute concentration.

Question 12

A cell membrane is described as selectively permeable. What does this mean?

Accepted Answer

Some substances can cross the membrane more easily than others.

Question 13

Which of the following would most likely increase the rate of diffusion of a small, nonpolar molecule across a lipid bilayer?

Accepted Answer

Increasing the concentration gradient across the membrane.

Question 14

Which of the following best explains why aquaporins are necessary in some cells?

Accepted Answer

Water is polar and crosses the membrane slowly; aquaporins increase the rate of water movement.

Question 15

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

Accepted Answer

The cells will shrink as water leaves them.

Question 16

Which of the following is a real-world example of facilitated diffusion?

Accepted Answer

Glucose entering a muscle cell through a GLUT transporter.

Question 17

Which of the following best describes the energy requirements for passive transport?

Accepted Answer

It does not require energy input; substances move down their concentration gradients.

Question 18

Which of the following is true about the movement of large polar molecules across the plasma membrane?

Accepted Answer

They require specific transport proteins to cross the membrane.

Question 19

Which of the following best describes the function of a symporter in secondary active transport?

Accepted Answer

It moves two different solutes in the same direction, using the energy from one solute moving down its gradient to transport the other against its gradient.

Question 20

A cell is placed in an isotonic solution. What will happen to the cell's volume over time?

Accepted Answer

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

Lipids, Membranes, and Transport: Structure and Function of the Plasma Membrane

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