Question 1

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

Accepted Answer

Protein synthesis and initial processing of secreted and membrane proteins

Question 2

A newly synthesized protein destined for secretion from the cell will most likely be synthesized by:

Accepted Answer

Ribosomes attached to the rough ER

Question 3

Which of the following modifications is most likely to occur to a protein as it passes through the Golgi apparatus?

Accepted Answer

Glycosylation and sulfation of tyrosines

Question 4

The ER and mitochondria are closely related in lipid biosynthesis because:

Accepted Answer

The ER supplies lipids to mitochondria, which cannot synthesize all their own lipids

Question 5

Which of the following best explains why lysosomes maintain an acidic pH?

Accepted Answer

To activate acid hydrolase enzymes for digestion

Question 6

A mutation that prevents the formation of COPII-coated vesicles would most directly affect which process?

Accepted Answer

Transport of proteins from the ER to the Golgi apparatus

Question 7

Which of the following statements about peroxisomes is correct?

Accepted Answer

They contain catalase and perform oxidation reactions without generating energy

Question 8

During autophagy, which sequence of events occurs to degrade damaged organelles?

Accepted Answer

Engulfment by autophagosome, fusion with lysosome, digestion by acid hydrolases

Question 9

Which of the following best describes the role of chaperone proteins in the ER?

Accepted Answer

They use ATP to assist in the proper folding of newly synthesized proteins

Question 10

A protein with a mutation in its N-terminal signal peptide is most likely to:

Accepted Answer

Be synthesized in the cytosol and fail to enter the ER

Question 11

Which of the following is a key difference between the vesicle transport and cisternal maturation models of protein movement through the Golgi apparatus?

Accepted Answer

Vesicle transport model proposes that cisternae remain stationary while cargo moves in vesicles; cisternal maturation model proposes that cisternae themselves move and mature

Question 12

Which of the following best describes the function of secretory vesicles in regulated secretion?

Accepted Answer

They store cargo and release it in response to specific signals

Question 13

Which of the following reactions is catalyzed by catalase in peroxisomes?

Accepted Answer

$$ \mathrm{H_2O_2 + R'H_2$ \rightarrow 2 H_2O + R'} $$

Question 14

A cell is observed to have a defect in vesicle trafficking, resulting in accumulation of proteins in the ER. Which organelle is most likely malfunctioning?

Accepted Answer

Golgi apparatus

Question 15

Which of the following statements about the endomembrane system is correct?

Accepted Answer

The ER communicates with the Golgi apparatus, which then sorts proteins to their destinations

Question 16

Which of the following best explains why only properly folded proteins leave the ER?

Accepted Answer

Quality control mechanisms retain misfolded proteins in the ER to prevent malfunction in the cell

Question 17

Which of the following is a function of the Golgi apparatus?

Accepted Answer

Sorting and further modification of proteins and lipids

Question 18

A patient has a genetic defect in the H$$^+-$$ATPase of lysosomes. Which of the following is the most likely consequence?

Accepted Answer

Lysosomal pH will become less acidic, reducing the activity of acid hydrolases

Question 19

Which of the following best describes the role of peroxisomes in the cell?

Accepted Answer

They perform oxidation reactions using catalase and other enzymes, important for detoxification and lipid metabolism

The Endomembrane System: Structure, Function, and Trafficking in Eukaryotic Cells

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