Question 1

Which type of cell junction is responsible for allowing the direct passage of ions and small molecules between adjacent animal cells, and is essential for synchronized contraction in heart muscle?

Accepted Answer

Gap junctions

Question 2

Which of the following statements best describes the function of tight junctions in epithelial tissues?

Accepted Answer

They prevent leakage of extracellular fluid by sealing neighboring cells together.

Question 3

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

Accepted Answer

Cell-to-cell communication via gap junctions

Question 4

Which cell junction is unique to plant cells and allows the passage of water, ions, and macromolecules between adjacent cells?

Accepted Answer

Plasmodesmata

Question 5

Which of the following best describes the cytoskeletal connection of desmosomes?

Accepted Answer

They connect to intermediate filaments such as keratin.

Question 6

A patient presents with blistering of the skin due to a genetic defect in cadherin proteins. Which cell junction is most likely affected?

Accepted Answer

Desmosomes

Question 7

Which of the following equations correctly represents the relationship between the number of connexin subunits ($$n) $$and the number of gap junction channels ($$C) $$formed, if each channel is made of 12 connexin subunits?

Accepted Answer

$$C = n/12$$

Question 8

Which cell junction is primarily responsible for anchoring epithelial cells to the basal lamina, and what is the main transmembrane protein involved?

Accepted Answer

Hemidesmosome; integrin

Question 9

In the context of cancer metastasis, altered expression of which protein is most likely to affect cell migration on the extracellular matrix?

Accepted Answer

Integrin

Question 10

Which of the following best explains why tight junctions are critical in the blood-brain barrier (BBB)?

Accepted Answer

They prevent paracellular movement of substances, maintaining a selective barrier.

Question 11

Which combination of proteins and cytoskeletal elements is correctly matched for adherens junctions?

Accepted Answer

Cadherins and actin microfilaments

Question 12

A researcher observes that phagocytes can migrate between endothelial cells during inflammation due to the loss of a specific cell junction. Which junction is most likely affected?

Accepted Answer

Tight junctions

Question 13

Which of the following is a key difference between desmosomes and hemidesmosomes?

Accepted Answer

Desmosomes use cadherins for cell-cell adhesion, while hemidesmosomes use integrins for cell-ECM adhesion.

Question 14

Which of the following best describes the role of focal adhesions in cell biology?

Accepted Answer

They connect actin microfilaments to the extracellular matrix via integrins.

Question 15

Which of the following scenarios would most likely result from a loss-of-function mutation in the gene encoding claudin?

Accepted Answer

Increased paracellular leakage in epithelial tissues

Question 16

Which of the following cell junctions is most likely to be disrupted in a patient with a genetic disorder causing muscle tears during strenuous activity?

Accepted Answer

Desmosomes

Question 17

Which of the following best describes the molecular composition of a gap junction channel?

Accepted Answer

It is formed by connexin proteins arranged in a hexameric structure.

Question 18

Which of the following is a correct sequence of events for the passage of a small ion from one smooth muscle cell to another during uterine contraction?

Accepted Answer

Ion passes through gap junctions formed by connexins

Question 19

Which of the following best explains why adherens junctions are important in the maintenance of tissue architecture in the intestine?

Accepted Answer

They form adhesion belts that connect actin filaments of neighboring cells, providing mechanical stability.

Cell Junctions: Structure, Function, and Genetic Relevance

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