Q: Which of the following equations correctly represents the net movement of ions per cycle of the sodium-potassium pump?

$$3\ \mathrm{Na}^+_{\text{in}} + 2\ \mathrm{K}^+_{\text{out}} \rightarrow 3\ \mathrm{Na}^+_{\text{out}} + 2\ \mathrm{K}^+_{\text{in}}$$

Question 1

Which of the following best describes the main function of the sodium-potassium pump in animal cells?

Accepted Answer

It uses ATP to actively transport 3 Na$$^+$$ ions out of the cell and 2 K$$^+$$ ions into the cell.

Question 2

During the operation of the sodium-potassium pump, what is the immediate effect of phosphorylation by ATP?

Accepted Answer

It causes the pump to change shape and release Na$$^+$$ ions outside the cell.

Question 3

Which of the following cell types is most likely to have a high density of sodium-potassium pumps?

Accepted Answer

Neurons, because they rely on ion gradients for action potentials.

Question 4

Which of the following equations correctly represents the net movement of ions per cycle of the sodium-potassium pump?

Accepted Answer

$$3\ \mathrm{Na}^+_{	ext{in}} + 2\ \mathrm{K}^+_{	ext{out}} ightarrow 3\ \mathrm{Na}^+_{	ext{out}} + 2\ \mathrm{K}^+_{	ext{in}}$$

Question 5

Exocytosis and endocytosis are classified as which type of transport?

Accepted Answer

Active transport, because they require energy to move large molecules across the membrane.

Question 6

Which of the following best explains how exocytosis uses vesicles to transport materials?

Accepted Answer

Vesicles fuse with the plasma membrane, releasing their contents outside the cell.

Question 7

Which type of molecules are most commonly transported by exocytosis?

Accepted Answer

Large molecules such as proteins and polysaccharides.

Question 8

A white blood cell engulfs a bacterium by extending its membrane around the bacterium and enclosing it in a vesicle. This process is best described as:

Accepted Answer

Phagocytosis

Question 9

Which of the following statements best distinguishes pinocytosis from phagocytosis?

Accepted Answer

Pinocytosis is nonspecific uptake of extracellular fluid, while phagocytosis engulfs large particles or cells.

Question 10

Which of the following is a key feature of receptor-mediated endocytosis?

Accepted Answer

It uses specific receptors to concentrate and internalize particular molecules even if they are in low concentration.

Question 11

A cell needs to import large quantities of cholesterol, which is present at low concentrations in the extracellular fluid. Which process will the cell most likely use?

Accepted Answer

Receptor-mediated endocytosis

Question 12

After a vesicle formed by receptor-mediated endocytosis releases its contents, what typically happens to the receptors?

Accepted Answer

They are recycled back to the plasma membrane.

Question 13

Which of the following best describes the energy requirements for the sodium-potassium pump?

Accepted Answer

It requires the hydrolysis of one ATP molecule per cycle.

Question 14

A mutation causes a cell to lose the ability to phosphorylate the sodium-potassium pump. What is the most likely consequence?

Accepted Answer

The pump will not change shape to release Na$$^+$$ ions outside the cell.

Question 15

Which of the following scenarios best illustrates bulk transport in a cell?

Accepted Answer

A pancreatic cell releasing insulin into the bloodstream via vesicles.

Question 16

Which of the following is NOT a characteristic of pinocytosis?

Accepted Answer

It requires the formation of pseudopodia.

Question 17

A scientist observes a cell forming a vesicle coated with proteins on its cytoplasmic side, which contains only specific molecules bound to membrane receptors. Which process is being observed?

Accepted Answer

Receptor-mediated endocytosis

Question 18

Which of the following best explains why exocytosis and endocytosis are necessary for transporting certain molecules across the plasma membrane?

Accepted Answer

They enable the transport of large macromolecules and particles that cannot cross the membrane by diffusion or transport proteins.

Question 19

Which of the following is a direct result of the sodium-potassium pump's activity in animal cells?

Accepted Answer

The inside of the cell becomes more negative relative to the outside.

Question 20

A patient has a genetic disorder that prevents the recycling of receptors after receptor-mediated endocytosis. What is a likely consequence?

Accepted Answer

The cell will gradually lose its ability to take up specific molecules from the extracellular fluid.

Active and Bulk Transport Mechanisms in Cells

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