Q: Which equation best represents the stoichiometry of the Na$$^+-K$^+$$ ATPase pump during one cycle?

$$3\ \mathrm{Na}^+_{\text{(in)}} + 2\ \mathrm{K}^+_{\text{(out)}} + \mathrm{ATP} \rightarrow 3\ \mathrm{Na}^+_{\text{(out)}} + 2\ \mathrm{K}^+_{\text{(in)}} + \mathrm{ADP} + \mathrm{P_i}$$

Question 1

Which of the following best describes the main difference between primary and secondary active transport across the plasma membrane?

Accepted Answer

Primary active transport uses energy directly from ATP hydrolysis, while secondary active transport uses energy indirectly from ionic gradients created by primary active transport.

Question 2

A patient is given a drug that inhibits the Na$$^+-K$^+$$ ATPase pump. Which of the following would most likely occur as a direct result?

Accepted Answer

The concentration gradient of Na$$^+$$ and K$$^+$$ across the plasma membrane would decrease.

Question 3

Which equation best represents the stoichiometry of the Na$$^+-K$^+$$ ATPase pump during one cycle?

Accepted Answer

$$3\ \mathrm{Na}^+_{	ext{(in)}} + 2\ \mathrm{K}^+_{	ext{(out)}} + \mathrm{ATP} ightarrow 3\ \mathrm{Na}^+_{	ext{(out)}} + 2\ \mathrm{K}^+_{	ext{(in)}} + \mathrm{ADP} + \mathrm{P_i}$$

Question 4

Which of the following is a real-life example of secondary active transport in the human body?

Accepted Answer

Glucose absorption in the small intestine via Na$$^+-$$glucose symporters.

Question 5

A cell is placed in a solution containing a high concentration of a toxin that blocks K$$^+$$ leakage channels. What is the most likely effect on the resting membrane potential (RMP)?

Accepted Answer

The RMP would become less negative (depolarize) because K$$^+$$ cannot leave the cell.

Question 6

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

Accepted Answer

K$$^+$$ diffuses out of the cell through leakage channels, leaving behind negatively charged proteins that cannot cross the membrane.

Question 7

Which of the following is NOT a characteristic of receptor-mediated endocytosis?

Accepted Answer

It is a nonspecific process that engulfs extracellular fluid and solutes.

Question 8

Which of the following best describes the function of antiporters in secondary active transport?

Accepted Answer

They move two different substances in opposite directions across the membrane.

Question 9

A patient is exposed to botulinum toxin, which blocks exocytosis of acetylcholine at the neuromuscular junction. What is the most likely clinical effect?

Accepted Answer

Muscle paralysis due to failure of neurotransmitter release.

Question 10

Which of the following best describes pinocytosis?

Accepted Answer

It is a nonspecific process in which the cell engulfs extracellular fluid and dissolved solutes.

Question 11

Which of the following statements about the Na$$^+-K$^+$$ pump is correct?

Accepted Answer

It helps maintain the resting membrane potential by pumping 3 Na$$^+$$ out and 2 K$$^+ in $$against their concentration gradients.

Question 12

Which of the following is a direct result of the Na$$^+-K$^+$$ pump's activity in excitable cells such as neurons and muscle cells?

Accepted Answer

Establishment and maintenance of electrochemical gradients necessary for action potentials.

Question 13

Which of the following best explains why secondary active transport is considered 'secondary'?

Accepted Answer

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

Question 14

A cell is actively engulfing a bacterium using pseudopods. Which process is occurring?

Accepted Answer

Phagocytosis

Question 15

Which of the following best describes the effect of ouabain (a cardiac glycoside) on the Na$$^+-K$^+$$ ATPase?

Accepted Answer

It inhibits the pump, leading to increased intracellular Na$$^+$$ and altered cardiac function.

Question 16

Which of the following is true regarding the resting membrane potential (RMP) in most cells?

Accepted Answer

The RMP is typically around $$-80\ \mathrm{mV}$$, with the inside of the cell being more negative than the outside.

Question 17

Which of the following best describes exocytosis?

Accepted Answer

It is the process by which cells expel materials using vesicles that fuse with the plasma membrane.

Question 18

Which of the following scenarios best illustrates the concept of an electrochemical gradient?

Accepted Answer

K$$^+$$ ions are driven out of the cell by their concentration gradient but pulled back in by the negative charge inside the cell.

Active Membrane Transport and Membrane Potential in Cells

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