Question 1

Which cytoskeletal element is primarily responsible for maintaining cell shape and resisting mechanical stress in animal cells?

Accepted Answer

Intermediate filaments

Question 2

In eukaryotic cells, microtubule assembly is regulated by the presence of a GTP cap. What is the main function of the GTP cap in microtubule dynamics?

Accepted Answer

It stabilizes the microtubule and prevents depolymerization.

Question 3

A patient is treated with paclitaxel (taxol) for cancer. What effect does this drug have on microtubules?

Accepted Answer

It stabilizes microtubules, preventing their depolymerization.

Question 4

Which protein is the primary building block of microfilaments in eukaryotic cells?

Accepted Answer

Actin

Question 5

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

Accepted Answer

G-actin is the monomeric form, while F-actin is the filamentous polymer.

Question 6

Which cytoskeletal element in bacteria is functionally analogous to eukaryotic microtubules?

Accepted Answer

FtsZ

Question 7

During mitosis, what is the primary function of the kinetochore?

Accepted Answer

It attaches chromosomes to spindle microtubules for proper segregation.

Question 8

Which junction is most important for preventing paracellular transport in epithelial cells?

Accepted Answer

Tight junctions

Question 9

What is the main difference between homophilic and heterophilic cell-cell interactions?

Accepted Answer

Homophilic interactions involve identical molecules binding, heterophilic involve different molecules binding.

Question 10

Which protein attaches muscle cells to the extracellular matrix (ECM)?

Accepted Answer

Dystrophin

Question 11

What is the plant cell analog to animal gap junctions, allowing for intercellular communication?

Accepted Answer

Plasmodesmata

Question 12

Which molecule is the most abundant component of the extracellular matrix (ECM) in animal tissues?

Accepted Answer

Collagen

Question 13

A cell loses attachment to the ECM layer. Which process prevents it from growing and dividing?

Accepted Answer

Anoikis

Question 14

Which stage of the cell cycle is typically the longest in most eukaryotic cells?

Accepted Answer

G1 phase

Question 15

What is the primary target of mitotic cyclins, and what is the mechanism by which they regulate mitosis?

Accepted Answer

Mitotic cyclins activate cyclin-dependent kinases (CDKs), which phosphorylate proteins to initiate mitosis.

Question 16

A mutation in the Rb protein prevents it from binding E2F. What is the likely consequence for the cell cycle?

Accepted Answer

The cell will enter S phase without proper regulation, increasing risk of uncontrolled division.

Question 17

Which pathway is directly involved in promoting cell growth and survival by activating Akt?

Accepted Answer

PI 3-Kinase pathway

Question 18

What is the main difference between apoptosis and necrosis?

Accepted Answer

Apoptosis is a controlled, programmed cell death; necrosis is uncontrolled and often results from injury.

Question 19

During cytokinesis in animal cells, what structure forms to divide the cytoplasm?

Accepted Answer

Cleavage furrow

Question 20

A cell is exposed to DNA damage. Which protein is most likely to halt the cell cycle and initiate apoptosis?

Accepted Answer

p53

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