Q: Which of the following equations correctly represents the action of the Na$$^+-K$^+$$ pump?

$$3\text{Na}^+_{\text{in}} + 2\text{K}^+_{\text{out}} + \text{ATP} \rightarrow 3\text{Na}^+_{\text{out}} + 2\text{K}^+_{\text{in}} + \text{ADP} + \text{P}_i$$

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 stored in ionic gradients created by primary active transport.

Question 2

The sodium-potassium pump (Na$$^+-K$^+$$ ATPase) is essential for maintaining the resting membrane potential in excitable cells. Which of the following correctly describes its action?

Accepted Answer

It pumps 3 Na$$^+$$ ions out of the cell and 2 K$$^+$$ ions into the cell, using energy from ATP.

Question 3

Which of the following is an example of secondary active transport in the small intestine?

Accepted Answer

Na$$^+-$$glucose symporter transporting glucose into the cell along with Na$$^+.$$

Question 4

A patient is diagnosed with a genetic disorder that impairs the function of clathrin-coated pits. Which cellular process would be most directly affected?

Accepted Answer

Receptor-mediated endocytosis

Question 5

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

Accepted Answer

K$$^+$$ ions diffuse out of the cell through leakage channels, while negatively charged proteins remain inside.

Question 6

Which of the following equations correctly represents the action of the Na$$^+-K$^+$$ pump?

Accepted Answer

$$3	ext{Na}^+_{	ext{in}} + 2	ext{K}^+_{	ext{out}} + 	ext{ATP} ightarrow 3	ext{Na}^+_{	ext{out}} + 2	ext{K}^+_{	ext{in}} + 	ext{ADP} + 	ext{P}_i$$

Question 7

Which of the following processes is best described as 'cell drinking' and is important for nutrient absorption in the small intestine?

Accepted Answer

Pinocytosis

Question 8

A white blood cell engulfs a bacterium by extending pseudopods around it and enclosing it in a vesicle. This process is called:

Accepted Answer

Phagocytosis

Question 9

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

Accepted Answer

Facilitating the movement of ions across the plasma membrane

Question 10

Which of the following best describes the role of G protein–linked receptors in cell signaling?

Accepted Answer

They activate G proteins, which then trigger intracellular second messengers such as cyclic AMP or calcium.

Question 11

A cell is exposed to a toxin that blocks all ATP production. Which of the following processes would be most immediately affected?

Accepted Answer

Primary active transport

Question 12

Which of the following is a real-life example of receptor-mediated endocytosis?

Accepted Answer

Uptake of low-density lipoproteins (LDL) by cells

Question 13

Which of the following statements about the resting membrane potential (RMP) is correct?

Accepted Answer

The RMP is mainly established by the movement of K$$^+$$ out of the cell through leakage channels.

Question 14

Which of the following best describes exocytosis?

Accepted Answer

A process where materials are ejected from the cell in vesicles that fuse with the plasma membrane.

Question 15

Which of the following is true regarding the electrochemical gradient across the plasma membrane?

Accepted Answer

It is maintained by the Na$$^+-K$^+$$ pump, which moves Na$$^+$$ out and K$$^+ in $$against their gradients.

Question 16

Which of the following best explains why Cl$$^-$$ does not influence the resting membrane potential in most cells?

Accepted Answer

Its concentration and electrical gradients are exactly balanced.

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