Question 1

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

Accepted Answer

Synthesis and initial modification of proteins destined for secretion or membrane insertion

Question 2

A mutation causes ribosomes to be unable to attach to the rough ER. Which cellular process would be most directly affected?

Accepted Answer

Export of proteins out of the cell

Question 3

Which organelle is primarily responsible for modifying, sorting, and packaging proteins received from the ER?

Accepted Answer

Golgi apparatus

Question 4

Steroid hormones such as testosterone and cortisol are synthesized in which part of the cell?

Accepted Answer

Smooth endoplasmic reticulum

Question 5

Which of the following best explains why proteins destined for export are synthesized on ribosomes attached to the rough ER rather than free ribosomes?

Accepted Answer

The rough ER provides a unique environment for proper folding and post-translational modification of exported proteins.

Question 6

A patient develops tolerance to a drug after repeated use. Which cellular adaptation is most likely responsible for this phenomenon?

Accepted Answer

Increased expression of cytochrome P450 enzymes in the smooth ER

Question 7

Which of the following best describes the flow of proteins through the endomembrane system?

Accepted Answer

Rough ER → transport vesicle → cis Golgi → trans Golgi → plasma membrane

Question 8

Which equation best represents the relationship between the rate of drug metabolism ($$v) $$and the concentration of cytochrome P450 enzymes ($$[E]) in $$the smooth ER, assuming substrate is not limiting?

Accepted Answer

$$v = k 	imes [E]$$

Question 9

During muscle contraction, which organelle releases calcium ions ($$Ca^{2+}) $$into the cytoplasm?

Accepted Answer

Smooth endoplasmic reticulum (sarcoplasmic reticulum)

Question 10

A cell is observed to have an abnormally high number of transport vesicles budding from the rough ER. Which process is most likely upregulated in this cell?

Accepted Answer

Protein secretion

Question 11

Which of the following is a direct consequence of increased cytochrome P450 activity in liver cells?

Accepted Answer

Increased breakdown of drugs, leading to drug tolerance

Question 12

Which of the following best explains why anabolic steroids can cause testicular atrophy?

Accepted Answer

Exogenous steroids suppress the pituitary release of growth factors, reducing endogenous testosterone production.

Question 13

Which face of the Golgi apparatus receives vesicles from the ER?

Accepted Answer

Cis face

Question 14

If a protein is incorrectly folded in the ER, what is the most likely fate of this protein?

Accepted Answer

It is targeted for degradation by the cell's quality control mechanisms.

Question 15

Which of the following is NOT a function of the smooth endoplasmic reticulum?

Accepted Answer

Protein glycosylation

Question 16

A scientist isolates a cell with abundant rough ER and Golgi apparatus. Which type of cell is this most likely to be?

Accepted Answer

A pancreatic cell specialized for secreting digestive enzymes

Question 17

Which of the following best describes the role of transport vesicles in the endomembrane system?

Accepted Answer

They move molecules between organelles such as the ER and Golgi apparatus.

Question 18

Which of the following scenarios would most likely result in a cell failing to secrete proteins?

Accepted Answer

A mutation prevents vesicle formation at the rough ER.

Question 19

Which of the following is the correct sequence for the synthesis and export of a secretory protein?

Accepted Answer

Nucleus → cytoplasm → rough ER → Golgi apparatus → plasma membrane

Question 20

Which of the following best explains why the endomembrane system is essential for maintaining cellular homeostasis?

Accepted Answer

It coordinates the synthesis, modification, and transport of proteins and lipids throughout the cell.

The Endomembrane System and Endoplasmic Reticulum in Eukaryotic Cells

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