Question 1

Which of the following best describes the main difference between the rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER)?

Accepted Answer

RER is studded with ribosomes and specializes in cotranslational import and protein folding, while SER lacks ribosomes and is involved in lipid metabolism and detoxification.

Question 2

A single-pass transmembrane protein is being synthesized. At which point does cotranslational import differ from that of a multi-pass transmembrane protein?

Accepted Answer

When the N-terminus faces the ER lumen for single-pass proteins, but multiple integral membrane proteins may have either the N- or C-terminus facing the lumen.

Question 3

Which of the following is a function of the sarcoplasmic reticulum in muscle contraction?

Accepted Answer

It stores and releases calcium ions ($$Ca^{2+}) to $$regulate muscle contraction.

Question 4

Which molecule is synthesized in the smooth ER and is essential for membrane structure and hormone production?

Accepted Answer

Cholesterol

Question 5

Which of the following best describes the difference between the cis Golgi network and the trans Golgi network?

Accepted Answer

The cis Golgi network receives vesicles from the ER, while the trans Golgi network sorts and ships proteins to their final destinations.

Question 6

During glycosylation, why must the growing core oligosaccharide flip to face the ER lumen?

Accepted Answer

Because the final glycosylated protein must be oriented toward the ER lumen for proper folding and trafficking.

Question 7

Which step in protein trafficking determines whether a protein is destined for secretion or retention in the ER?

Accepted Answer

Recognition of ER retention or retrieval signals, such as the KDEL sequence.

Question 8

Which type of endocytosis involves the specific uptake of molecules via receptor-ligand interactions and clathrin-coated pits?

Accepted Answer

Receptor-mediated endocytosis

Question 9

Which coat protein is responsible for vesicle transport from the Golgi to the plasma membrane?

Accepted Answer

Clathrin

Question 10

What is the primary function of peroxisomes in eukaryotic cells?

Accepted Answer

Catalase-mediated breakdown of hydrogen peroxide ($$2H_2O_2 \rightarrow 2H_2O + O_2$)

Question 11

Which cytoskeletal filament is composed of tubulin monomers and is involved in chromosome separation during mitosis?

Accepted Answer

Microtubules

Question 12

What is the role of the GTP cap in microtubule dynamics?

Accepted Answer

It stabilizes the growing end of the microtubule and prevents depolymerization.

Question 13

Which drug disrupts microtubule polymerization and is used in cancer therapy to inhibit cell division?

Accepted Answer

Colchicine

Question 14

A cell is observed to have defective microtubule-organizing centers (MTOCs). Which cellular process is most likely to be impaired?

Accepted Answer

Chromosome segregation during mitosis

Question 15

Which microtubule-associated protein is known to regulate microtubule stability and is implicated in neurodegenerative diseases when abnormally phosphorylated?

Accepted Answer

Tau

Question 16

Which of the following statements about microfilaments is correct?

Accepted Answer

Microfilaments are composed of actin monomers and are involved in cell movement and shape.

Question 17

What is the difference between G-actin and F-actin in microfilaments?

Accepted Answer

G-actin is the globular monomer, while F-actin is the filamentous polymer formed by G-actin subunits.

Question 18

Which process best describes dynamic instability in microtubules?

Accepted Answer

The rapid switching between growth and shrinkage at microtubule ends due to GTP hydrolysis.

Question 19

Which protein is required for vesicle fusion with target membranes and is essential for neurotransmitter release?

Accepted Answer

SNARE

Question 20

A patient is diagnosed with a genetic disorder affecting the function of catalase. Which cellular organelle is most likely to be dysfunctional?

Accepted Answer

Peroxisome

Endomembrane System and Cytoskeleton: Study Guide Notes

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Study Guide - Flashcards