Question 1

Which of the following best describes the two major physical properties of molecules that determine their ability to diffuse across a biological membrane by simple diffusion?

Accepted Answer

Molecular size and polarity

Question 2

A red blood cell is placed in a solution and begins to swell and eventually bursts. Which term best describes the solution, and what is the direction of water movement?

Accepted Answer

The solution is hypotonic; water moves into the cell.

Question 3

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It requires a specific membrane protein but does not require energy input.

Question 4

Which of the following best describes the function of aquaporins in cellular membranes?

Accepted Answer

They facilitate the rapid movement of water molecules across the membrane.

Question 5

A cell uses the Na+/K+ ATPase pump to maintain its membrane potential. Which of the following statements is TRUE regarding this pump?

Accepted Answer

It moves 3 Na+ ions out of the cell and 2 K+ ions into the cell per ATP hydrolyzed.

Question 6

Which of the following best distinguishes between direct and indirect active transport?

Accepted Answer

Direct active transport uses ATP directly, while indirect active transport relies on gradients established by ATP hydrolysis.

Question 7

Which of the following equations correctly represents the free energy change ($$\Delta G) $$for the transport of an uncharged solute across a membrane?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[S]_{in}}{[S]_{out}} \right)$$

Question 8

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

Water will leave the cells, causing them to shrink (crenate).

Question 9

Which of the following is an example of a symport transporter?

Accepted Answer

The Na+/glucose transporter, which moves both Na+ and glucose into the cell together.

Question 10

Which of the following statements about the kinetics of simple diffusion versus facilitated diffusion is correct?

Accepted Answer

Facilitated diffusion exhibits saturation kinetics, while simple diffusion does not.

Question 11

A cell is placed in an isotonic solution. Which of the following best describes the net movement of water?

Accepted Answer

There is no net movement of water across the membrane.

Question 12

Which of the following best describes the analogy between carrier proteins in facilitated diffusion and enzymes?

Accepted Answer

Both exhibit specificity and saturation kinetics for their substrates.

Question 13

A researcher measures the membrane potential of a neuron and finds it to be -70 mV. What does this value indicate?

Accepted Answer

The inside of the membrane is 70 mV more negative than the outside.

Question 14

Which of the following best describes an antiport transporter?

Accepted Answer

It moves two different solutes in opposite directions across the membrane.

Question 15

A cell uses the Na+/glucose transporter to import glucose against its concentration gradient. Which of the following statements is correct?

Accepted Answer

The transporter uses the energy stored in the Na+ gradient to drive glucose uptake.

Question 16

Which of the following is NOT a characteristic of simple diffusion across a membrane?

Accepted Answer

It is saturable at high solute concentrations.

Question 17

A scientist wants to calculate the free energy change ($$\Delta G) $$for the movement of a charged ion across a membrane. Which equation should they use?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[S]_{in}}{[S]_{out}} \right) + zF\Delta E$$

Question 18

Which of the following scenarios best illustrates indirect active transport?

Accepted Answer

The Na+/glucose symporter uses the Na+ gradient established by the Na+/K+ ATPase to import glucose.

Question 19

Which of the following would most likely increase the rate of simple diffusion of a molecule across a membrane?

Accepted Answer

Decreasing the size and increasing the nonpolarity of the molecule.

Question 20

A mutation in the Glut1 transporter reduces its affinity for glucose. Which of the following is the most likely effect on glucose uptake by the cell at low glucose concentrations?

Accepted Answer

Glucose uptake will decrease because the transporter is less effective at binding glucose.

Transport Across Membranes: Mechanisms and Energetics

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