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 Processes

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

Possible Answers:

microtubule cytoskeleton . . . integrins

microtubule cytoskeleton . . . cadherins

actin cytoskeleton . . . cadherins

intermediate filament 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 #1 : Signals, Communication, And 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 and III

I, II, and III

III and IV

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

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

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

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
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