Question 1

Which of the following best explains why eukaryotic cells benefit from having intracellular compartments?

Accepted Answer

They allow for simultaneous, potentially conflicting metabolic processes to occur in different regions of the cell.

Question 2

A liver cell exposed to high levels of phenobarbital shows an increase in which organelle, and why?

Accepted Answer

Smooth ER, because it contains enzymes for drug detoxification such as cytochrome P-450.

Question 3

Which of the following is a function of the Golgi apparatus?

Accepted Answer

Protein modification, sorting, and packaging into vesicles for transport.

Question 4

A mutation in the gene encoding the signal recognition particle (SRP) would most directly affect which process?

Accepted Answer

Cotranslational import of proteins into the ER.

Question 5

Which of the following best describes the role of flippases in membrane biosynthesis?

Accepted Answer

They transfer specific phospholipids from the cytosolic to the lumenal leaflet of the ER membrane, contributing to membrane asymmetry.

Question 6

A protein with the C-terminal sequence Lys-Asp-Glu-Leu (KDEL) is most likely to:

Accepted Answer

Be retrieved from the Golgi and returned to the ER.

Question 7

Which process is responsible for the uptake of cholesterol into mammalian cells?

Accepted Answer

Receptor-mediated endocytosis

Question 8

A patient with a mutation in a gene encoding a specific cytochrome P-450 enzyme experiences severe side effects from a standard drug dose. This is an example of:

Accepted Answer

Pharmacogenetics

Question 9

Which of the following steps is NOT part of the cotranslational import of a protein into the ER?

Accepted Answer

The protein is fully synthesized in the cytosol before import.

Question 10

Which of the following best describes the difference between constitutive and regulated secretion?

Accepted Answer

Constitutive secretion is continuous and unregulated, while regulated secretion requires a specific signal to trigger vesicle fusion with the plasma membrane.

Question 11

A protein destined for the lysosome is most likely to:

Accepted Answer

Be tagged with a specific oligosaccharide in the Golgi apparatus.

Question 12

Which of the following is a direct result of the activity of protein disulfide isomerase in the ER?

Accepted Answer

Formation and rearrangement of disulfide bonds in newly synthesized proteins.

Question 13

A cell is observed to have an accumulation of misfolded proteins in the ER. Which cellular response is most likely to be activated?

Accepted Answer

The unfolded protein response (UPR)

Question 14

Which of the following best describes the role of the translocon during cotranslational import?

Accepted Answer

It forms a channel in the ER membrane through which the growing polypeptide is translocated.

Question 15

Which of the following is a key difference between the stationary cisternae model and the cisternal maturation model of Golgi function?

Accepted Answer

In the stationary cisternae model, cisternae are stable and cargo is shuttled by vesicles; in the cisternal maturation model, cisternae themselves mature and move through the stack.

Question 16

A protein is found to be secreted from a cell, but when its N-terminal signal sequence is deleted, it remains in the cytosol. This experiment demonstrates that:

Accepted Answer

The signal sequence is necessary for targeting the protein to the ER for secretion.

Question 17

Which of the following best describes the fate of a plasma membrane receptor after ligand binding and endocytosis?

Accepted Answer

It is often recycled back to the plasma membrane after dissociation from the ligand in the early endosome.

Question 18

Which of the following is a direct consequence of exocytosis in animal cells?

Accepted Answer

Addition of new lipids and proteins to the plasma membrane.

Question 19

A mutation that disrupts the function of the ATP-dependent calcium ATPase in the sarcoplasmic reticulum would most likely affect which process?

Accepted Answer

Muscle contraction due to impaired calcium storage and release.

Question 20

Which of the following best describes the process of retrograde transport in the endomembrane system?

Accepted Answer

Movement of vesicles from the Golgi apparatus back to the ER, allowing for recycling of proteins and membrane components.

The Endomembrane System and Protein Sorting: Structure, Function, and Trafficking

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