Question 1

Which equation best describes the free energy change ($$\Delta G_A) $$for the transport of ion A across a membrane, considering both concentration and electrical potential differences?

Accepted Answer

$$\Delta G_A = RT \ln \left( \frac{[A]_{in}}{[A]_{out}} \right) + Z_A F \Delta \Psi$$

Question 2

A cell maintains a higher concentration of K$$^+$$ inside than outside. If the membrane potential ($$\Delta \Psi) is $$negative inside, what is the direction of spontaneous K$$^+$$ flow?

Accepted Answer

Out of the cell, because both concentration and electrical gradients favor efflux

Question 3

Which of the following statements about passive-mediated transport is correct?

Accepted Answer

It occurs through specific membrane proteins and does not require cellular energy

Question 4

Facilitated diffusion differs from simple diffusion in that:

Accepted Answer

It requires a membrane protein to assist the movement of polar or charged molecules

Question 5

Which of the following is a feature of channel-forming ionophores?

Accepted Answer

They form continuous aqueous pores through which ions can diffuse

Question 6

Aquaporins are specialized for the transport of which molecule?

Accepted Answer

Water

Question 7

Which type of transporter moves two different substances in opposite directions across a membrane?

Accepted Answer

Antiport

Question 8

The sodium-potassium pump (Na$$^+/K$^+-$$ATPase) transports:

Accepted Answer

3 Na$$^+$$ out and 2 K$$^+ in $$per ATP hydrolyzed

Question 9

Which statement best describes primary active transport?

Accepted Answer

It uses ATP directly to move substances against their concentration gradient

Question 10

GLUT1 is an example of which type of transporter?

Accepted Answer

Uniport

Question 11

Which of the following is true about ABC transporters?

Accepted Answer

They use ATP hydrolysis to drive the transport of various substrates across membranes

Question 12

A mutation in the aquaporin gene would most likely affect which cellular process?

Accepted Answer

Regulation of water balance across the cell membrane

Question 13

Which of the following best explains why facilitated diffusion is saturable?

Accepted Answer

Transport rate is limited by the number of available transport proteins

Question 14

In secondary active transport, the energy for moving a molecule against its gradient comes from:

Accepted Answer

The movement of another molecule down its gradient

Question 15

Which of the following is NOT a characteristic of passive transport?

Accepted Answer

Requires energy input from ATP hydrolysis

Question 16

A cell is placed in a solution with a higher concentration of glucose than inside the cell. Which transport process will most likely occur?

Accepted Answer

Facilitated diffusion of glucose into the cell

Question 17

Which of the following best describes the role of ATP in the sodium-potassium pump?

Accepted Answer

ATP hydrolysis provides energy for conformational changes that move Na$$^+$$ and K$$^+$$ against their gradients

Question 18

Which of the following is a real-life example of secondary active transport?

Accepted Answer

Glucose uptake in the intestine via Na$$^+-$$glucose symporter

Question 19

If the concentration of ion A is 10 mM inside the cell and 1 mM outside, and the membrane potential is zero, what is the free energy change ($$\Delta G_A) $$for the transport of A into the cell at 25°C? (Assume $$R = 8.314 J/$$mol·K, $$T = 298 K)$$

Accepted Answer

$$\Delta G_A = 8.314 	imes 298 	imes \ln \left( \frac{10}{1} ight)$$

Question 20

Which statement about ionophores is correct?

Accepted Answer

Carrier ionophores bind ions and shuttle them across the membrane, while channel-forming ionophores create pores for ion passage

Membrane Transport: Thermodynamics, Mechanisms, and Transport Proteins

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