Question 1

Which of the following molecules is most likely to cross a biological membrane via simple diffusion?

Accepted Answer

O$$_2$$

Question 2

What is the primary difference between facilitated diffusion and simple diffusion across a membrane?

Accepted Answer

Facilitated diffusion requires a membrane protein, while simple diffusion does not.

Question 3

Which equation best describes the initial velocity of glucose entry via GLUT1 transporter?

Accepted Answer

$$V_o = V_{max} [S_{out}] / (K_t + [S_{out}])$$

Question 4

Ion channels differ from transporters in which of the following ways?

Accepted Answer

Ion channels can be specific for certain ions but are not saturable, while transporters are saturable.

Question 5

A mutation in the S4 segment of a voltage-gated ion channel would most likely affect which property?

Accepted Answer

The ability of the channel to sense changes in membrane potential

Question 6

Which of the following best explains why polar or charged molecules have low permeability across the lipid bilayer?

Accepted Answer

They must shed their solvation layer, which is energetically unfavorable.

Question 7

Which of the following statements about the GLUT1 transporter is TRUE?

Accepted Answer

GLUT1 is a passive transporter that facilitates diffusion of glucose.

Question 8

The effect of 6-benzyl-D-galactose on GLUT1 double reciprocal plots is most similar to which type of enzyme inhibition?

Accepted Answer

Competitive inhibition

Question 9

Which of the following is a function of aquaporin channels in biological membranes?

Accepted Answer

Allow passage of water molecules while preventing proton hopping

Question 10

During an action potential, which event occurs first in a neuron?

Accepted Answer

Depolarization due to opening of voltage-gated Na$$^{+}$$ channels

Question 11

Which of the following best describes the 'rocking bananas' mechanism of transporters?

Accepted Answer

A transporter alternates between two conformations to move substrate across the membrane

Question 12

Which of the following is TRUE regarding the permeability of biological membranes?

Accepted Answer

Nonpolar small molecules have higher permeability than polar large molecules.

Question 13

Which of the following transport systems is an example of antiport?

Accepted Answer

Chloride-bicarbonate exchange protein

Question 14

What is the main reason facilitated diffusion by a passive transporter shows saturation kinetics?

Accepted Answer

The transporter can only bind a limited number of substrate molecules at a time.

Question 15

Which of the following is NOT a way that ion channels can be gated?

Accepted Answer

By ATP hydrolysis

Question 16

A patient with a mutation that prevents the 'ball and chain' inactivation of voltage-gated Na$$^{+}$$ channels would most likely experience which effect?

Accepted Answer

Prolonged action potentials due to delayed channel closing

Question 17

Which of the following statements about passive transporters is FALSE?

Accepted Answer

They require energy input from ATP.

Question 18

Insulin regulates glucose transporters by which mechanism?

Accepted Answer

Increasing the number of glucose transporters on the plasma membrane via vesicle fusion

Question 19

Which of the following best describes the direction of movement for K$$^{+}$$ ions through the potassium channel?

Accepted Answer

Down their concentration gradient

Question 20

Which of the following is a characteristic of uniport transport systems?

Accepted Answer

They transport a single type of molecule in one direction across the membrane.

Membrane Transport I: Mechanisms and Proteins in Biological Membranes

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