Question 1

Which of the following best explains why phospholipids form bilayers in aqueous environments?

Accepted Answer

Their hydrophilic heads interact with water, while their hydrophobic tails avoid water, causing the tails to face inward and the heads to face outward.

Question 2

A red blood cell is placed in a hypertonic solution. Which process occurs, and what is the result for the cell?

Accepted Answer

Water leaves the cell by osmosis, causing it to shrink and crenate.

Question 3

Which of the following best describes the mechanism by which glucose enters liver cells when the intracellular glucose concentration is higher than the extracellular concentration?

Accepted Answer

Active transport using a sodium-glucose symporter, moving glucose against its concentration gradient.

Question 4

Which equation correctly represents the calculation of the concentration gradient for a solute across a membrane?

Accepted Answer

$$C_{gradient} = C_{outside} - C_{inside}$$

Question 5

A patient is given a drug that inhibits the Na	extsuperscript{+}/K	extsuperscript{+} ATPase pump. What is the most likely immediate effect on membrane potential?

Accepted Answer

The membrane potential becomes less negative (depolarizes) due to accumulation of Na	extsuperscript{+} inside the cell.

Question 6

Which of the following is an example of secondary active transport?

Accepted Answer

Uptake of glucose into intestinal cells via a sodium-glucose symporter.

Question 7

Which of the following best explains why chronic cocaine use leads to decreased sensitivity to dopamine in the brain?

Accepted Answer

Cocaine blocks dopamine reuptake, causing prolonged high dopamine levels, which leads to downregulation of dopamine receptors.

Question 8

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It uses channel or carrier proteins to move molecules down their concentration gradient.

Question 9

A cell is observed to engulf large particles by wrapping its plasma membrane around them and forming a vesicle. Which process is being described?

Accepted Answer

Phagocytosis

Question 10

Which of the following best describes the role of dopamine transporter proteins (DATs) in normal synaptic transmission?

Accepted Answer

They facilitate the reuptake of dopamine from the synaptic cleft back into the presynaptic neuron.

Question 11

Which of the following would most likely increase the fluidity of a cell membrane at room temperature?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in phospholipids.

Question 12

A cancer cell is found to be resistant to chemotherapy because it actively pumps out the drug using a membrane protein. Which type of transport is most likely responsible?

Accepted Answer

Active transport using an ATP-dependent pump

Question 13

Which of the following best explains why large, polar molecules cannot cross the plasma membrane by simple diffusion?

Accepted Answer

They are repelled by the hydrophobic core of the lipid bilayer.

Question 14

Which of the following best describes the effect of blocking dopamine reuptake transporters (DATs) on synaptic dopamine levels?

Accepted Answer

Dopamine levels in the synaptic cleft increase and remain elevated.

Question 15

Which of the following is a consequence of chronic downregulation of dopamine receptors in the brain?

Accepted Answer

Decreased sensitivity to both natural and drug-induced rewards.

Question 16

Which of the following best describes the lining of the interior of a sodium channel pore in the plasma membrane?

Accepted Answer

Polar or charged amino acids to interact with Na	extsuperscript{+} ions.

Question 17

Which of the following best explains why ATP is required for the Na	extsuperscript{+}/K	extsuperscript{+} pump to function?

Accepted Answer

The pump moves Na	extsuperscript{+} and K	extsuperscript{+} against their concentration gradients, which requires energy input from ATP hydrolysis.

Question 18

A neuron is exposed to a drug that blocks vesicular release of neurotransmitters. Which step of synaptic transmission is directly affected?

Accepted Answer

Release of neurotransmitter into the synaptic cleft.

Question 19

Which of the following best describes the process of exocytosis?

Accepted Answer

Release of substances from the cell by fusion of a vesicle with the plasma membrane.

Membrane Transport and Its Role in Physiology and Drug Addiction

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