GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Junction Types

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Example Questions

Example Question #1 : Cellular Junctions

Adherens junctions are specialized cell junctions that form by linking the __________ to transmembrane proteins known as __________.

Possible Answers:

actin cytoskeleton . . . cadherins

microtubule cytoskeleton . . . cadherins

intermediate filament cytoskeleton . . . integrins

microtubule cytoskeleton . . . integrins

Correct answer:

actin cytoskeleton . . . cadherins

Explanation:

Adherens junctions are formed by linking the actin cytoskeleton to transmembrane proteins known as cadherins. Cadherins are capable of interacting with other cadherins from neighboring cells on the exoplasmic face of the cell membrane. This interaction forms a physical link essentially connecting the actin cytoskeletons of the two adjacent cells, thus promoting force transduction.

Desmosomes are another type of cell junction that link the intermediate filaments of the cytoskeleton to cadherins.

Example Question #2 : Cellular Junctions

Which of the following cell junctions is involved with anchoring the extracellular matrix to the cell?

I. Adherens junctions

II. Desmosomes

III. Hemidesmosomes

IV. Gap junctions

Possible Answers:

I, II, III, and IV

I, II, and III

III and IV

I and III

Correct answer:

I and III

Explanation:

Of the choices, only adherens junctions and hemidesmosomes are responsible for anchoring the extracellular matrix. This is accomplished by associating the actin cytoskeleton (for adherens junctions) or the intermediate filament cytoskeleton (for hemidesmosomes) with transmembrane proteins known as integrins. Integrins interact with the extracellular matrix.

Desmosomes are responsible for anchoring adjacent cells to one another by connecting their intermediate filament cytoskeletons with cadherins. Gap junctions connect the cytoplasm of adjacent cells and allow the free flow of small molecules between them. 

Example Question #1 : Help With Junction Types

Which of the following statements is NOT TRUE about gap junctions?

Possible Answers:

Gap junctions prevent molecules and ions from traveling between cells in the extracellular space. 

Gap junctions form channels that are comprised of connexin proteins. 

Gap junctions permit the travel of small molecules back and forth between adjacent cells. 

Gap junctions contribute to electrical coupling of adjacent cells. 

Gap junctions have some functionality of permitting cells to adhere to one another. 

Correct answer:

Gap junctions prevent molecules and ions from traveling between cells in the extracellular space. 

Explanation:

"Gap junctions prevent molecules and ions from traveling between cells in the extracellular space" is incorrect because this describes the function of tight junctions. Gap junctions electrically couple two cells by permitting the formation of small channels that connect two cells. 

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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