Question 1

Which of the following best describes the function of a patch clamp technique in membrane biochemistry?

Accepted Answer

It enables the observation of ion movement across single membrane channels.

Question 2

Which of the following is NOT one of the three main classes of membrane transporter proteins?

Accepted Answer

Receptors

Question 3

Simple diffusion across a membrane is most likely to occur with which type of molecule?

Accepted Answer

Lipophilic molecules

Question 4

Facilitated diffusion is considered passive transport because:

Accepted Answer

The energy driving ion movement originates from the ion gradient itself.

Question 5

Which equation correctly represents the free energy change ($$\Delta G) $$for moving a charged species across a membrane?

Accepted Answer

$$\Delta G = RT \ln (c_2$/c_1$) + ZF \Delta V$$

Question 6

What is the primary energetic cost associated with active transport of ions across a membrane?

Accepted Answer

It requires input of energy, often from ATP hydrolysis.

Question 7

The Na$$^+-K$^+$$ ATPase pump transports ions in which ratio per catalytic cycle?

Accepted Answer

3 Na$$^+$$ out, 2 K$$^+ in$$

Question 8

Which of the following is a characteristic of P-type ATPases?

Accepted Answer

They form a phosphorylated aspartate intermediate during their catalytic cycle.

Question 9

Multidrug-resistance (MDR) proteins are classified as which type of transporter?

Accepted Answer

ABC transporter

Question 10

Secondary active transport differs from primary active transport in that:

Accepted Answer

It couples the unfavorable flow of one species to the favorable flow of another down its gradient.

Question 11

Which of the following best describes a symporter?

Accepted Answer

A carrier that transports two substrates in the same direction.

Question 12

Lactose permease in E. coli is an example of:

Accepted Answer

A symporter that uses the H$$^+$$ gradient to drive lactose uptake

Question 13

Which statement about ion channels is correct?

Accepted Answer

They allow rapid, passive movement of ions across membranes.

Question 14

During an action potential, what triggers the opening of voltage-gated Na$$^+$$ channels?

Accepted Answer

Depolarization of the membrane beyond a threshold value (e.g., -40 mV)

Question 15

The ball-and-chain model explains which aspect of ion channel function?

Accepted Answer

Channel inactivation by occlusion of the pore

Question 16

Which of the following is true about the acetylcholine receptor?

Accepted Answer

It is a ligand-gated channel that opens upon acetylcholine binding.

Question 17

Gap junctions are formed by the joining of two:

Accepted Answer

Connexons from neighboring cells

Question 18

Aquaporins selectively transport water across membranes. Which feature prevents the passage of protons?

Accepted Answer

Positively charged residues toward the center of the channel

Question 19

During the refractory period of an action potential:

Accepted Answer

A new action potential cannot be induced.

Question 20

Which of the following best describes the equilibrium potential for an ion?

Accepted Answer

It is the membrane potential at which the driving force due to the concentration gradient is balanced by the electrostatic force.

Membrane Channels and Pumps: Mechanisms of Transport Across Biological Membranes

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