Question 1

Which of the following best describes the main function of the rough endoplasmic reticulum (RER) in eukaryotic cells?

Accepted Answer

Synthesis of membrane and secretory proteins, and initial glycosylation of glycoproteins

Question 2

A genetic defect in the enzyme responsible for adding mannose-6-phosphate to lysosomal enzymes would most likely result in which cellular phenotype?

Accepted Answer

Accumulation of undigested substrates in lysosomes due to mis-targeting of hydrolases

Question 3

Which of the following is TRUE regarding the directionality of protein trafficking through the Golgi apparatus?

Accepted Answer

Proteins move from the ER to the CGN, then through the medial cisternae, and finally to the TGN during anterograde transport

Question 4

Which of the following best explains why muscle and brain cells cannot release free glucose into the bloodstream?

Accepted Answer

They lack the enzyme glucose-6-phosphatase in their smooth ER

Question 5

A patient with familial hypercholesterolemia (FH) is found to have a mutation that prevents LDL receptors from being delivered to the plasma membrane. What is the most likely consequence?

Accepted Answer

LDL particles accumulate in the blood, leading to increased cholesterol synthesis in cells

Question 6

Which of the following statements about the SNARE hypothesis is CORRECT?

Accepted Answer

v-SNAREs on vesicles interact specifically with t-SNAREs on target membranes to mediate vesicle fusion

Question 7

Which of the following best describes the role of clathrin in receptor-mediated endocytosis?

Accepted Answer

Clathrin forms a protein coat around vesicles, selecting cargo and shaping the vesicle

Question 8

Which of the following is a key difference between exocytosis and endocytosis?

Accepted Answer

Exocytosis releases materials outside the cell, while endocytosis brings materials into the cell

Question 9

Which of the following best explains why peroxisomes are not considered part of the endomembrane system?

Accepted Answer

Peroxisomes are not derived from the ER and have a unique biogenesis pathway

Question 10

A pulse-chase experiment is performed using radioactive amino acids. After a short pulse, most radioactivity is found in the rough ER. After a longer chase, the radioactivity is found in the Golgi and then in secretory vesicles. What does this experiment demonstrate?

Accepted Answer

Proteins are synthesized in the ER and transported through the Golgi to secretory vesicles before secretion

Question 11

Which of the following is a function of the smooth endoplasmic reticulum (SER) in liver cells?

Accepted Answer

Drug detoxification via cytochrome P450-catalyzed hydroxylation

Question 12

Which of the following best describes the fate of LDL particles after receptor-mediated endocytosis?

Accepted Answer

LDL is delivered to lysosomes for degradation, while the receptor is recycled to the plasma membrane

Question 13

Which of the following is a consequence of a defect in the KDEL retrieval signal of ER-resident proteins?

Accepted Answer

ER-resident proteins are secreted from the cell instead of being retained in the ER

Question 14

Which of the following best describes the process of autophagy?

Accepted Answer

A double membrane derived from the ER encloses damaged organelles for degradation in lysosomes

Question 15

Which of the following is a function of peroxisomes?

Accepted Answer

Hydrogen peroxide metabolism and oxidation of fatty acids

Question 16

Which of the following best explains the feedback regulation of cholesterol synthesis in cells?

Accepted Answer

Low intracellular cholesterol due to defective LDL uptake signals increased cholesterol synthesis

Question 17

Which of the following is a key role of Rab proteins in vesicular transport?

Accepted Answer

They help specify which vesicle fuses with which target membrane

Question 18

Which of the following is TRUE about the role of COPII and COPI in vesicular transport?

Accepted Answer

COPII mediates transport from the ER to the cis-Golgi, while COPI mediates retrograde transport from the Golgi to the ER

Question 19

Which of the following best describes the function of dynamin in receptor-mediated endocytosis?

Accepted Answer

It is a GTPase that pinches off clathrin-coated vesicles from the plasma membrane

Question 20

Which of the following diseases is associated with a defect in lysosomal enzyme targeting, leading to accumulation of waste materials in lysosomes?

Accepted Answer

I-cell disease (mucolipidosis II)

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

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