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

$$ \Pi = RT \left( [\text{solute}]_{\text{in}} - [\text{solute}]_{\text{out}} \right) $$

Question 1

Which property most directly explains why water-soluble molecules and ions have difficulty crossing a protein-free lipid bilayer?

Accepted Answer

Their polarity and charge are incompatible with the hydrophobic interior of the bilayer.

Question 2

A cell is placed in a solution containing a high concentration of glucose. Which mechanism would most likely allow glucose to enter the cell rapidly?

Accepted Answer

Facilitated diffusion via a glucose transporter.

Question 3

Which equation best describes the electrochemical gradient for an ion across a membrane?

Accepted Answer

$$ \Delta G = RT \ln \left( \frac{[	ext{ion}]_{	ext{out}}}{[	ext{ion}]_{	ext{in}}} ight) + zF\Delta V $$

Question 4

Which of the following best describes the difference between transporters and channels?

Accepted Answer

Transporters undergo conformational changes to move solutes, while channels form a continuous pore for rapid passage.

Question 5

Which statement correctly describes the resting membrane potential of a typical animal cell?

Accepted Answer

It is negative inside relative to outside, primarily due to potassium leak channels.

Question 6

A toxin, ouabain, inhibits the sodium-potassium pump. What is the most immediate effect on the cell?

Accepted Answer

The cell will accumulate sodium ions in the cytosol and lose the ability to maintain its resting membrane potential.

Question 7

Which of the following is NOT a source of energy for active transport by transmembrane pumps?

Accepted Answer

Facilitated diffusion

Question 8

In intestinal epithelial cells, which transporter is responsible for importing glucose from the gut lumen?

Accepted Answer

Glucose-sodium symport

Question 9

Which equation describes the osmotic pressure ($$\Pi) $$across a cell membrane?

Accepted Answer

$$ \Pi = RT \left( [	ext{solute}]_{	ext{in}} - [	ext{solute}]_{	ext{out}} ight) $$

Question 10

Which mechanism do plant cells use to maintain osmotic equilibrium when placed in hypotonic solutions?

Accepted Answer

They rely on their rigid cell wall to prevent excessive swelling.

Question 11

Which of the following best describes a symport?

Accepted Answer

A transporter that moves two solutes in the same direction across the membrane.

Question 12

How do animal cells keep the cytosolic concentration of calcium ions low?

Accepted Answer

By actively pumping calcium out of the cytosol using ATP-driven pumps.

Question 13

Which statement best explains how ion channels achieve ion selectivity?

Accepted Answer

Their pore size and specific amino acid residues allow only certain ions to pass.

Question 14

Patch-clamp recording is used to study ion channels by:

Accepted Answer

Isolating a small patch of membrane and recording the current through individual ion channels.

Question 15

Which of the following is an example of a voltage-gated ion channel?

Accepted Answer

Sodium channel in neurons

Question 16

During an action potential, which sequence of events occurs in the Na$$^+-$$gated ion channel?

Accepted Answer

Closed → Open → Inactivated → Closed

Question 17

Which neurotransmitter receptor is associated with excitatory postsynaptic potentials in vertebrate muscle cells?

Accepted Answer

Acetylcholine receptor

Question 18

Curare and strychnine both affect neurotransmitter receptors. Which statement correctly describes their mechanisms?

Accepted Answer

Curare blocks acetylcholine receptors, while strychnine blocks glycine receptors.

Question 19

Which drug acts by inhibiting serotonin reuptake in nerve cells, thereby affecting mood?

Accepted Answer

Prozac

Question 20

A nerve cell receives both excitatory and inhibitory signals. Which process allows it to integrate these inputs and generate an appropriate response?

Accepted Answer

Summation of postsynaptic potentials at the axon hillock.

Chapter 12: Cell Biology Study Guide: Membrane Transport and Ion Channels

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