Question 1

Which of the following best explains why organelles in eukaryotic cells do not become homogenized despite constant membrane flow between them?

Accepted Answer

The presence of organelle-specific identity markers that selectively import and export proteins

Question 2

During clathrin-mediated endocytosis, which molecule is responsible for the scission of the vesicle from the plasma membrane?

Accepted Answer

Dynamin, a GTPase that hydrolyzes GTP to cause membrane scission

Question 3

Which equation best describes the energetic cost of membrane bending during vesicle formation?

Accepted Answer

$$\Delta G \propto \frac{1}{r}$$, where $$r is $$the diameter of membrane curvature

Question 4

A mutation in dynamin prevents the hydrolysis of GTP. What is the most likely cellular consequence?

Accepted Answer

Vesicle budding is arrested, leading to impaired endocytosis and paralysis in neurons

Question 5

Which molecule regulates the assembly and disassembly of clathrin coats at the plasma membrane?

Accepted Answer

Phosphatidylinositol-4,5-bisphosphate (PIP2)

Question 6

What is the primary function of adaptor protein complex 2 (AP2) in clathrin-mediated endocytosis?

Accepted Answer

It links cargo receptors to clathrin, enabling cargo selection and coat assembly

Question 7

Which GTPase is responsible for regulating the assembly of COPII coats on the ER membrane?

Accepted Answer

Sar1 GTPase

Question 8

A cell is unable to deliver newly synthesized proteins from the ER to the Golgi. Which protein coat is most likely defective?

Accepted Answer

COPII

Question 9

Which of the following steps is NOT directly involved in vesicle fusion with a target membrane?

Accepted Answer

Cargo selection by adaptor proteins

Question 10

Which process is responsible for the uptake of cholesterol (LDL) from the extracellular space into the cell?

Accepted Answer

Receptor-mediated endocytosis

Question 11

What is the role of SNARE proteins in vesicular transport?

Accepted Answer

They mediate the specific fusion of vesicle and target membranes

Question 12

Which of the following best describes the biosynthetic pathway in vesicle transport?

Accepted Answer

Delivery of newly synthesized proteins and membrane from the ER to other organelles

Question 13

Which protein coat is primarily involved in vesicle formation at the plasma membrane for endocytosis?

Accepted Answer

Clathrin

Question 14

A patient has a genetic defect in the mannose-6-phosphate receptor. Which cellular process will be most affected?

Accepted Answer

Delivery of hydrolytic enzymes to the lysosome

Question 15

Which of the following is a correct sequence for the steps of clathrin-mediated endocytosis?

Accepted Answer

Cargo selection, coat assembly, bud formation, membrane scission, uncoating

Question 16

Which equation describes the molecular switch mechanism of GTPases involved in vesicle trafficking?

Accepted Answer

$$	ext{GTPase}_{	ext{active}} + 	ext{GTP} \xrightarrow{	ext{hydrolysis}} 	ext{GTPase}_{	ext{inactive}} + 	ext{GDP}$$

Question 17

Which of the following is TRUE regarding Rab GTPases?

Accepted Answer

They are organelle-specific and mediate vesicle tethering to target compartments

Question 18

Which real-world example illustrates the importance of SNARE proteins in human health?

Accepted Answer

Botulinum and tetanus toxins attack SNAREs, blocking neurotransmitter release and causing paralysis

Question 19

Which of the following is a function of exocytosis in immune cells?

Accepted Answer

Secretion of histamines by mast cells during inflammation

Vesicle Transport: Mechanisms, Protein Coats, and Organelle Targeting in Eukaryotic Cells

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