Question 1

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

Accepted Answer

Synthesis of membrane-bound and secretory proteins via ribosomes attached to its surface

Question 2

A protein destined for secretion from a eukaryotic cell is synthesized and processed through which sequence of organelles?

Accepted Answer

Rough ER → Golgi apparatus → secretory vesicle → plasma membrane

Question 3

Which of the following modifications is responsible for targeting soluble lysosomal enzymes to lysosomes?

Accepted Answer

Glycosylation and phosphorylation of mannose residues to form mannose-6-phosphate

Question 4

During the process of glycosylation in the ER, what is the role of flippase enzymes?

Accepted Answer

They transfer newly synthesized phospholipids from the cytosolic to the lumenal leaflet of the ER membrane

Question 5

Which of the following best explains 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 6

A mutation in the gene encoding the v-SNARE protein would most likely affect which cellular process?

Accepted Answer

Fusion of transport vesicles with their target membranes

Question 7

Which of the following tags is responsible for the retention of proteins in the endoplasmic reticulum (ER) until they are properly assembled?

Accepted Answer

RXR tag

Question 8

What is the main function of the cis-Golgi network (CGN) in the Golgi apparatus?

Accepted Answer

Receiving and sorting proteins arriving from the ER

Question 9

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

Accepted Answer

Movement of vesicles from the Golgi apparatus back to the ER

Question 10

A drop in pH marks the maturation of endosomes into lysosomes. Which mechanism is primarily responsible for this pH change?

Accepted Answer

V-type proton pumps in the endosome membrane

Question 11

Which of the following is a direct result of exocytosis in a secretory cell?

Accepted Answer

The vesicle membrane becomes part of the plasma membrane

Question 12

Which of the following best describes the process of protein glycosylation in the ER and Golgi apparatus?

Accepted Answer

Addition and modification of carbohydrate side chains on proteins

Question 13

A protein with a KDEL sequence at its C-terminus is most likely to:

Accepted Answer

Be retrieved from the Golgi and returned to the ER

Question 14

Which of the following best explains the role of SNARE proteins in vesicle trafficking?

Accepted Answer

They mediate the specific fusion of vesicles with their target membranes

Question 15

Which of the following is a key difference between rough and smooth endoplasmic reticulum?

Accepted Answer

Rough ER is studded with ribosomes and involved in protein synthesis, while smooth ER lacks ribosomes and is involved in lipid synthesis

Question 16

Which of the following best describes the process of endocytosis?

Accepted Answer

The plasma membrane invaginates to form a vesicle that brings extracellular material into the cell

Question 17

Which of the following scenarios best illustrates polarized secretion?

Accepted Answer

Digestive enzymes are secreted only on the side of an intestinal cell facing the gut lumen

Question 18

Which of the following statements about the Golgi apparatus is correct?

Accepted Answer

It modifies, sorts, and packages proteins and lipids received from the ER

Question 19

A researcher observes that a secreted protein is transiently found in anterograde transition vesicles. What does this indicate about the protein's trafficking pathway?

Accepted Answer

It is moving from the ER to the Golgi apparatus as part of the secretory pathway

Question 20

Which of the following best explains why the addition of carbohydrate side chains to proteins (glycosylation) is important in the endomembrane system?

Accepted Answer

Glycosylation is critical for proper protein folding, stability, and targeting to specific cellular locations

Organelles and Cellular Trafficking: The Endomembrane System

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