Q: Which equation best represents the initial step of phospholipid synthesis in the ER?

$$\text{Fatty acyl CoA} + \text{Glycerol 3-phosphate} \rightarrow \text{Phosphatidic acid} + \text{CoA}$$

Question 1

Which organelle is primarily responsible for the biosynthesis and initial processing of membrane and secretory proteins in eukaryotic cells?

Accepted Answer

Rough endoplasmic reticulum

Question 2

What is the main function of flippases in the endoplasmic reticulum membrane?

Accepted Answer

Transferring newly synthesized lipids from the cytosolic side to the lumenal side of the bilayer

Question 3

A patient presents with a disorder in glycosylation, specifically affecting the addition of oligosaccharides to asparagine residues. Which process is most likely disrupted?

Accepted Answer

N-linked glycosylation

Question 4

Which of the following best describes the role of molecular chaperones such as BiP in the ER?

Accepted Answer

They facilitate the folding and assembly of polypeptides into multisubunit proteins.

Question 5

Which sequence acts as a retrieval tag for ER-resident proteins in mammals?

Accepted Answer

KDEL

Question 6

During the maturation of endosomes into lysosomes, which pH change occurs?

Accepted Answer

pH decreases from ~6.4 to ~4-5

Question 7

Which model of Golgi apparatus function proposes that cisternae are stable structures and transport occurs via shuttle vesicles?

Accepted Answer

Stationary cisternae model

Question 8

A mutation in the gene encoding Rab GTPase would most likely affect which cellular process?

Accepted Answer

Recognition and fusion of vesicles with their target membranes

Question 9

Which coat protein is most commonly associated with vesicles transporting material from the ER to the Golgi?

Accepted Answer

COPII

Question 10

Which of the following best describes the process of autophagy?

Accepted Answer

Breakdown of damaged or unneeded cellular structures by lysosomes

Question 11

Which equation best represents the initial step of phospholipid synthesis in the ER?

Accepted Answer

$$	ext{Fatty acyl CoA} + 	ext{Glycerol 3-phosphate} ightarrow 	ext{Phosphatidic acid} + 	ext{CoA}$$

Question 12

Which of the following is a function of the smooth endoplasmic reticulum?

Accepted Answer

Drug detoxification

Question 13

A protein with a hydrophobic domain length matching the medial cisternae of the Golgi is most likely to be incorporated into which region?

Accepted Answer

Medial cisternae

Question 14

Which process is described by the equation $$	ext{Anterograde transport}: 	ext{ER} ightarrow 	ext{Golgi} ightarrow 	ext{Plasma membrane}$$?

Accepted Answer

Movement of material toward the plasma membrane

Question 15

Which of the following is NOT a function of the Golgi apparatus?

Accepted Answer

Drug detoxification

Question 16

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

Accepted Answer

They mediate the fusion between vesicles and their target membranes.

Question 17

Which of the following statements about lysosomal enzymes is correct?

Accepted Answer

They are synthesized on the rough ER and delivered from the TGN to endosomes in transport vesicles.

Question 18

Which of the following is a plausible consequence of a defect in the unfolded protein response (UPR) in the ER?

Accepted Answer

Accumulation of misfolded proteins and cellular stress

Question 19

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

Import of extracellular molecules by forming vesicles from the plasma membrane using specific receptors

Ch. 12: The Endomembrane System and Protein Sorting: Structure, Function, and Trafficking

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