Question 1

Which of the following coat proteins is primarily responsible for vesicle transport from the endoplasmic reticulum (ER) to the Golgi apparatus?

Accepted Answer

COPII

Question 2

A mutation in the Sar1 G-protein prevents GTP hydrolysis. What is the most likely consequence for COPII vesicle formation?

Accepted Answer

Vesicles will remain coated and unable to fuse with the Golgi.

Question 3

Which retrieval signal sequence is responsible for returning soluble ER-resident proteins from the Golgi back to the ER?

Accepted Answer

KDEL (Lys-Asp-Glu-Leu)

Question 4

During vesicle trafficking, which class of proteins mediates the specificity and directionality of vesicle docking and fusion with target membranes?

Accepted Answer

SNARE proteins

Question 5

A cell is observed to have an accumulation of secretory proteins in the ER at 40°C, but these proteins move to the Golgi and plasma membrane at 32°C. What experimental tool is most likely being used to visualize this process?

Accepted Answer

Green Fluorescent Protein (GFP)-tagged temperature-sensitive mutant

Question 6

Which of the following best describes the cisternal maturation model of Golgi trafficking?

Accepted Answer

Golgi cisternae mature and change enzyme composition as they move from cis to trans.

Question 7

Which small G-protein is specifically associated with COPII coat assembly during ER-to-Golgi transport?

Accepted Answer

Sar1

Question 8

A patient’s pancreatic cells are found to have an unusually high number of Golgi stacks. What is the most likely explanation for this observation?

Accepted Answer

Pancreatic cells export large amounts of proteins, requiring extensive Golgi apparatus for processing.

Question 9

Which of the following equations correctly represents the hydrolysis of GTP by a small G-protein during vesicle coat disassembly?

Accepted Answer

$$\mathrm{GTP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{GDP} + \mathrm{P}_i$$

Question 10

Which of the following is TRUE regarding the role of Rab G-proteins in vesicle trafficking?

Accepted Answer

Rab-GTP is active and associated with membranes, mediating vesicle docking via Rab effectors.

Question 11

A researcher treats cells with a non-hydrolyzable analog of GTP (GTP-γ-S). What is the expected effect on vesicle trafficking?

Accepted Answer

Vesicles will be trapped in the coated form and unable to fuse with target membranes.

Question 12

Which of the following statements about cargo selection in vesicle trafficking is CORRECT?

Accepted Answer

Cargo receptors such as ERGIC-53 bind specific oligosaccharides and interact with coat proteins via their cytoplasmic domains.

Question 13

Which of the following best explains why COPI vesicles are found throughout the Golgi complex?

Accepted Answer

COPI vesicles mediate retrograde transport of enzymes from trans- to cis-Golgi compartments.

Question 14

A protein with a KDEL sequence at its C-terminus is found in the Golgi. What is the fate of this protein?

Accepted Answer

It will be retrieved back to the ER via COPI-coated vesicles.

Question 15

Which of the following is a direct consequence of the difference in pH between the ER and Golgi compartments?

Accepted Answer

It regulates the binding and release of KDEL-tagged proteins to the KDEL receptor.

Question 16

Which of the following is a function of the trans-Golgi network (TGN)?

Accepted Answer

Sorting and exit of vesicles to lysosomes, plasma membrane, or secretory pathway

Question 17

Which of the following best describes the role of SNARE proteins in vesicle fusion?

Accepted Answer

They bring vesicle and target membranes into close proximity to facilitate fusion.

Question 18

Which of the following is a plausible reason why some cargo proteins, such as pro-collagen fibers, cannot be trafficked in coated vesicles?

Accepted Answer

They are too large to fit inside the vesicles.

Question 19

Which of the following statements about the vesicular transport model of Golgi trafficking is CORRECT?

Accepted Answer

Golgi compartments are static and maintain their specific processing enzymes.

Vesicle Trafficking: From the Endoplasmic Reticulum (ER) to the Golgi Apparatus

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