$$ \mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy} $$

Question 1

Which of the following best describes the main function of the Na+-K+ ATPase pump in animal cells?

Accepted Answer

It maintains high intracellular K+ and high extracellular Na+ by pumping 3 Na+ out and 2 K+ in, using ATP.

Question 2

Which equation correctly represents the ATP hydrolysis reaction that powers primary active transport?

Accepted Answer

$$ \mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy} $$

Question 3

A patient is given a drug that blocks all vesicular transport in cells. Which of the following processes would be directly affected?

Accepted Answer

Exocytosis of neurotransmitters

Question 4

Which of the following is TRUE regarding secondary active transport?

Accepted Answer

It relies on the energy stored in ionic gradients established by primary active transport.

Question 5

In the Na+-K+ pump cycle, what is the immediate result of phosphorylation of the pump protein?

Accepted Answer

The pump changes shape and expels Na+ to the outside.

Question 6

Which of the following best explains why the inside of a resting cell membrane is negative relative to the outside?

Accepted Answer

K+ ions diffuse out of the cell through leakage channels, leaving behind negatively charged proteins.

Question 7

Which of the following is a correct description of receptor-mediated endocytosis?

Accepted Answer

It uses clathrin-coated pits to selectively internalize specific ligands.

Question 8

A mutation causes the Na+-K+ ATPase to transport only Na+ but not K+. What would be the most likely effect on the cell?

Accepted Answer

The cell would lose its resting membrane potential and ionic gradients would dissipate.

Question 9

Which of the following best describes the role of G proteins in cell signaling?

Accepted Answer

They act as molecular relays, transmitting signals from receptors to effector proteins inside the cell.

Question 10

Which of the following is an example of a symport system in secondary active transport?

Accepted Answer

Na+-glucose cotransporter moving both Na+ and glucose into the cell

Question 11

Which of the following equations best represents the Nernst equation for the equilibrium potential of K+?

Accepted Answer

$$ E_K = \frac{RT}{zF} \ln \left( \frac{[K^+]_{	ext{outside}}}{[K^+]_{	ext{inside}}} ight) $$

Question 12

Which of the following is NOT a function of cell adhesion molecules (CAMs)?

Accepted Answer

Synthesizing ATP for cellular energy

Question 13

Which process is most important for the uptake of cholesterol into cells?

Accepted Answer

Receptor-mediated endocytosis

Question 14

A neuron is at rest with a membrane potential of –70 mV. Which ion is primarily responsible for establishing this resting membrane potential?

Accepted Answer

K+

Question 15

Which of the following best describes the difference between phagocytosis and pinocytosis?

Accepted Answer

Phagocytosis engulfs large particles, while pinocytosis engulfs extracellular fluid and solutes.

Question 16

Which of the following is a direct result of ligand binding to a G protein–coupled receptor?

Accepted Answer

Activation of the G protein by exchange of GDP for GTP

Question 17

Which of the following is TRUE about exocytosis?

Accepted Answer

It involves the fusion of a vesicle with the plasma membrane to release contents outside the cell.

Question 18

Which of the following would most likely occur if the Na+-K+ pump stopped functioning in a neuron?

Accepted Answer

The neuron would lose its ionic gradients, leading to loss of excitability.

Question 19

Which of the following best describes the role of second messengers in cell signaling?

Accepted Answer

They relay and amplify signals from receptors to target molecules inside the cell.

Active Membrane Transport and Cell Signaling: Study Notes for Anatomy & Physiology

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