Question 1

Which of the following best describes the function of the KDEL sequence in protein trafficking?

Accepted Answer

It serves as a retrieval tag to return escaped ER-resident proteins from the Golgi back to the ER.

Question 2

A mutation changes the C-terminal KDEL sequence of a soluble ER protein to KDEV. What is the most likely consequence for this protein?

Accepted Answer

It will be secreted from the cell because it cannot be retrieved from the Golgi.

Question 3

Which of the following is a key difference between phagocytosis and pinocytosis?

Accepted Answer

Phagocytosis involves the uptake of large particles, while pinocytosis involves the uptake of fluids and small molecules.

Question 4

A cell is unable to internalize EGF/EGFR complexes due to a defect in clathrin-mediated endocytosis. What is the most likely cellular consequence?

Accepted Answer

EGFR will accumulate on the cell surface, leading to prolonged signaling.

Question 5

Which of the following best describes the role of SNARE proteins in vesicular transport?

Accepted Answer

They mediate the fusion of vesicle and target membranes by forming a complex between v-SNAREs and t-SNAREs.

Question 6

Which of the following reactions is catalyzed by catalase in peroxisomes?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 7

A protein with a hydrophobic domain is most likely to be:

Accepted Answer

A membrane protein embedded in the lipid bilayer.

Question 8

Which of the following best explains why peroxisomes are important for cellular metabolism?

Accepted Answer

They detoxify harmful substances by breaking down hydrogen peroxide and oxidizing fatty acids.

Question 9

During receptor-mediated endocytosis, which protein is primarily responsible for forming the coated pit that leads to vesicle formation?

Accepted Answer

Clathrin

Question 10

A patient has a genetic defect in the peroxin gene. Which cellular process is most likely to be impaired?

Accepted Answer

Import of proteins into the peroxisome.

Question 11

Which of the following best describes the fate of a lysosomal enzyme that fails to be glycosylated with mannose-6-phosphate in the Golgi?

Accepted Answer

It will be secreted from the cell instead of being delivered to the lysosome.

Question 12

Which of the following is a correct sequence of events in phagocytosis by a macrophage?

Accepted Answer

Adhesion and ingestion → Phagosome formation → Phagosolysosome formation → Degradation

Question 13

Which of the following best explains the role of dynamin in clathrin-mediated endocytosis?

Accepted Answer

It pinches off the clathrin-coated vesicle from the plasma membrane.

Question 14

A protein destined for the nucleus contains a nuclear localization signal (NLS). Which of the following best describes how this protein is imported?

Accepted Answer

It is imported post-translationally through nuclear pores via recognition of the NLS.

Question 15

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

Accepted Answer

Constitutive secretion occurs continuously, while regulated secretion requires a specific signal to trigger vesicle fusion with the plasma membrane.

Question 16

Which of the following is a function of peroxisomes that distinguishes them from lysosomes?

Accepted Answer

Breakdown of very long-chain fatty acids via beta-oxidation.

Question 17

A researcher observes that a certain membrane protein is not retained in the Golgi and is instead found in the plasma membrane. Which of the following is the most likely explanation?

Accepted Answer

The protein lacks a hydrophobic domain of sufficient length to anchor it in the Golgi membrane.

Question 18

Which of the following best describes the process of receptor recycling after receptor-mediated endocytosis?

Accepted Answer

Receptors are returned to the plasma membrane from early endosomes for reuse.

Protein Trafficking, Endomembrane System, and Vesicular Transport in Eukaryotic Cells

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