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, microtubules are assembled from which protein subunits?

Accepted Answer

Alpha-tubulin and beta-tubulin

Question 3

A scientist treats cells with nocodazole. What is the most likely effect on microtubules?

Accepted Answer

Microtubules depolymerize and disassemble

Question 4

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

Accepted Answer

MreB

Question 5

What is the role of the GTP cap in the dynamic instability of microtubules?

Accepted Answer

It stabilizes the microtubule and prevents rapid depolymerization

Question 6

Which protein is the main building block of microfilaments?

Accepted Answer

Actin

Question 7

A crawling cell extends its leading edge using which actin-based structure?

Accepted Answer

Lamellipodia

Question 8

Which cell-cell junction is primarily responsible for preventing paracellular transport in epithelial cells?

Accepted Answer

Tight junction

Question 9

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

Accepted Answer

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

Question 10

Which extracellular matrix component is most abundant in animal tissues?

Accepted Answer

Collagen

Question 11

A mutation in the gene encoding integrin would most likely affect which cellular process?

Accepted Answer

Cell attachment to the extracellular matrix

Question 12

Which process prevents cells from growing if they lose attachment to the ECM layer?

Accepted Answer

Anoikis

Question 13

What is the plant cell analog to animal gap junctions?

Accepted Answer

Plasmodesmata

Question 14

During mitosis, which stage is characterized by the alignment of chromosomes at the metaphase plate?

Accepted Answer

Metaphase

Question 15

Which checkpoint ensures that DNA is undamaged and fully replicated before mitosis begins?

Accepted Answer

G2/M checkpoint

Question 16

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

Accepted Answer

p53

Question 17

Which equation best describes the treadmilling phenomenon in actin filaments, where the rate of addition at the plus end equals the rate of loss at the minus end?

Accepted Answer

$$k_{on}^{+} = k_{off}^{-}$$

Question 18

A cell is treated with paclitaxel (taxol). What is the expected effect on microtubule dynamics?

Accepted Answer

Microtubules are stabilized and resist depolymerization

Question 19

Which mechanism is responsible for the separation of sister chromatids during anaphase?

Accepted Answer

Motor proteins moving along microtubules

Question 20

Which signaling pathway is directly involved in promoting cell growth and survival, often dysregulated in cancer?

Accepted Answer

PI 3-Kinase-Akt pathway

Cell Biology Exam 3 Study Guide – Step-by-Step Guidance

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