Question 1

Which of the following best describes the process of signal amplification in a GPCR signaling pathway?

Accepted Answer

A single ligand-bound receptor activates multiple G proteins, each of which can activate many downstream effectors, resulting in a large cellular response.

Question 2

A patient is given a drug that acts as an antagonist for a receptor tyrosine kinase (RTK). Which of the following would most likely be observed in the patient's cells?

Accepted Answer

Decreased autophosphorylation of the RTK and reduced activation of the MAP kinase cascade.

Question 3

Which of the following correctly matches a cytoskeletal element with its primary function?

Accepted Answer

Microtubules – Intracellular transport and chromosome segregation during mitosis.

Question 4

Colchicine is a drug that binds to tubulin and prevents microtubule polymerization. What is the most likely effect of colchicine on a dividing cell?

Accepted Answer

The cell will be unable to form a mitotic spindle, leading to cell cycle arrest in mitosis.

Question 5

Which of the following best explains the molecular basis of treadmilling in actin filaments?

Accepted Answer

ATP-actin subunits are added to the plus end while ADP-actin subunits dissociate from the minus end.

Question 6

A mutation in the gene encoding the Arp2/3 complex would most directly affect which cellular process?

Accepted Answer

Formation of branched actin networks in lamellipodia, impairing cell migration.

Question 7

Which of the following statements about the sliding filament model of muscle contraction is correct?

Accepted Answer

Myosin heads hydrolyze ATP, bind to actin, and pull actin filaments toward the center of the sarcomere.

Question 8

Which of the following best describes the role of gap junctions in animal cells?

Accepted Answer

They allow direct passage of ions and small molecules between adjacent cells, facilitating electrical and metabolic coupling.

Question 9

Which of the following is a correct sequence of events in the activation of the MAP kinase cascade by an RTK?

Accepted Answer

Ligand binding $$\rightarrow$$ receptor dimerization $$\rightarrow$$ autophosphorylation $$\rightarrow$$ adaptor protein recruitment $$\rightarrow$$ Ras activation $$\rightarrow$$ MAP kinase cascade.

Question 10

A researcher observes that a cell has a high concentration of cAMP following hormone stimulation. Which signaling pathway is most likely activated?

Accepted Answer

GPCR pathway involving Gsα activation of adenylyl cyclase.

Question 11

Which of the following best explains why taxol, a drug that stabilizes microtubules, is effective in cancer chemotherapy?

Accepted Answer

It prevents microtubule depolymerization, thereby blocking mitotic spindle function and inhibiting cell division.

Question 12

Which of the following statements about DNA packaging in eukaryotic cells is correct?

Accepted Answer

DNA wraps around histone proteins to form nucleosomes, which further fold into chromatin fibers.

Question 13

A mutation that disrupts the nuclear localization signal (NLS) of a protein would most likely result in which of the following?

Accepted Answer

The protein would remain in the cytoplasm and fail to enter the nucleus.

Question 14

Which of the following best describes the function of focal adhesions?

Accepted Answer

They connect the actin cytoskeleton of a cell to the extracellular matrix via integrins.

Question 15

During muscle contraction, which of the following events is directly triggered by an increase in cytosolic $$\mathrm{Ca$$^{2+}$$}$$ concentration?

Accepted Answer

$$\mathrm{Ca$$^{2+}$$}$$ binds to troponin, causing a conformational change that moves tropomyosin and exposes myosin-binding sites on actin.

Question 16

Which of the following statements about intermediate filaments is correct?

Accepted Answer

They provide mechanical strength to cells and are composed of various proteins such as keratins and lamins.

Question 17

A scientist is studying a protein that is exported from the nucleus to the cytoplasm. Which of the following is most likely required for this process?

Accepted Answer

A nuclear export signal (NES) and exportin proteins, with energy provided by GTP hydrolysis.

Question 18

Which of the following best describes the role of the basal lamina in tissues?

Accepted Answer

It provides structural support and separates epithelial cells from underlying connective tissue.

Question 19

Which of the following is a correct order of collagen fiber assembly in the extracellular matrix?

Accepted Answer

Procollagen synthesis $$\rightarrow$$ secretion $$\rightarrow$$ cleavage of propeptides $$\rightarrow$$ collagen fibril assembly.

Cell Biology Study Guide: Signal Transduction, Cytoskeleton, Cell Movement, Cell Junctions, ECM, and DNA/Nucleus

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