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 : Signals, Communication, And Junctions
Adherens junctions are specialized cell junctions that form by linking the __________ to transmembrane proteins known as __________.
microtubule cytoskeleton . . . cadherins
microtubule cytoskeleton . . . integrins
actin cytoskeleton . . . cadherins
intermediate filament cytoskeleton . . . integrins
actin cytoskeleton . . . cadherins
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 : 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
I and III
III and IV
I, II, III, and IV
I, II, and III
I and III
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?
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 have some functionality of permitting cells to adhere to one another.
Gap junctions contribute to electrical coupling of adjacent cells.
Gap junctions permit the travel of small molecules back and forth between adjacent cells.
Gap junctions prevent molecules and ions from traveling between cells in the extracellular space.
"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.
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