Question 1

Which method is most appropriate for separating organelles based on their density rather than their size?

Accepted Answer

Density gradient centrifugation

Question 2

A researcher wants to isolate mitochondria from a cell homogenate. Which sequence of centrifugation speeds should be used to obtain a pellet enriched in mitochondria?

Accepted Answer

Low speed, then medium speed

Question 3

The smooth endoplasmic reticulum (SER) in liver cells is primarily involved in which of the following processes?

Accepted Answer

Drug detoxification and glycogen catabolism

Question 4

Which enzyme, found in the smooth ER, is the target of statin drugs used to lower cholesterol?

Accepted Answer

Hydroxymethylglutaryl-CoA reductase (HMG-CoA reductase)

Question 5

What is the primary function of chaperone proteins in the rough endoplasmic reticulum (RER)?

Accepted Answer

To ensure newly synthesized proteins fold correctly

Question 6

A protein destined for the lysosome is tagged in the Golgi apparatus with which specific modification?

Accepted Answer

Phosphorylation of mannose residues (mannose-6-phosphate)

Question 7

Which of the following best describes the function of SNARE proteins in vesicular transport?

Accepted Answer

They mediate the specific fusion of vesicles with their target membranes

Question 8

A mutation in the gene encoding the KDEL retrieval tag would most likely result in which of the following?

Accepted Answer

Proteins meant for the ER being secreted from the cell

Question 9

Which of the following statements about flippases is correct?

Accepted Answer

They use ATP to move phospholipids from the cytosolic to the lumenal leaflet of the ER membrane

Question 10

A cell is observed to have a large number of clathrin-coated vesicles. Which process is most likely occurring at a high rate in this cell?

Accepted Answer

Receptor-mediated endocytosis

Question 11

Which of the following best explains why lysosomal enzymes do not digest the cell’s own cytosol under normal conditions?

Accepted Answer

Lysosomal enzymes are only active at acidic pH

Question 12

Which of the following is a function of peroxisomes in animal cells?

Accepted Answer

Detoxification of hydrogen peroxide via catalase

Question 13

A patient has a genetic defect in the enzyme superoxide dismutase (SOD) in peroxisomes. Which of the following would most likely accumulate in their cells?

Accepted Answer

Superoxide free radical ($$O_2$$^-$$)

Question 14

Which of the following best describes the process of autophagy?

Accepted Answer

Degradation of the cell’s own organelles within lysosomes

Question 15

Which of the following is a unique function of plant cell vacuoles not shared by lysosomes in animal cells?

Accepted Answer

Maintenance of turgor pressure

Question 16

Which of the following best explains the asymmetry of membrane phospholipids in eukaryotic cells?

Accepted Answer

Phospholipid translocators (flippases) selectively transfer specific phospholipids across the bilayer

Question 17

A protein with an RXR (Arg-X-Arg) sequence is found in the ER. What is the most likely fate of this protein?

Accepted Answer

It will be retained in the ER until properly assembled

Question 18

Which of the following is a direct consequence of anterograde transport in the secretory pathway?

Accepted Answer

Loss of ER membrane lipids to the plasma membrane

Question 19

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

Accepted Answer

Clathrin forms a coat that shapes the vesicle and selects cargo

Question 20

A cell is unable to recycle its membrane proteins from the Golgi back to the ER. Which process is most likely defective?

Accepted Answer

Retrograde transport

Eukaryotic Organelle Structure and Function: Isolation, Sorting, and Roles

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