GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Other Regulatory Mechanisms

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

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

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Example Questions

Example Question #4 : Enzyme Regulation

How do competitive inhibitors affect enzyme efficiency?

Possible Answers:

Raise the maximum rate of the enzymatic reaction

Raise the Michaelis constant

Lower the maximum rate of the enzymatic reaction

Lower the Michaelis constant

Correct answer:

Raise the Michaelis constant

Explanation:

Competitive inhibitors can be overpowered by introducing excess substrate, so they do not affect the maximum rate of the enzyme. They do, however, make it so that more substrate is required in order to get the enzyme working at half of its maximum rate. As a result, competitive inhibitors act by raising the Michaelis constant of enzymes.

Example Question #1 : Help With Other Regulatory Mechanisms

How does a noncomeptitive inhibitor affect an enzyme?

Possible Answers:

Lowers the maximum rate of the enzymatic reaction

Raises the Michaelis constant of the enzyme

Lowers the Michaelis constant of the enzyme

Raises the maximum rate of the enzymatic reaction

Correct answer:

Lowers the maximum rate of the enzymatic reaction

Explanation:

A noncompetitive inhibitor acts to decrease how fast the enzyme can act on substrates. It accomplishes this by lowering the maximum rate at which it can create products. Noncompetitive inhibitors do not alter the enzyme's Michaelis constant.

Example Question #2 : Help With Other Regulatory Mechanisms

How is pepsinogen activated in the stomach?

Possible Answers:

Cofactors bind to the enzyme, increasing its efficiency

It is phosphorylated by another enzyme

It is activated by the temperature change in the stomach lumen

A portion is cleaved, activating the enzyme

Correct answer:

A portion is cleaved, activating the enzyme

Explanation:

Once in the stomach lumen, pepsinogen finds itself in a very acidic environment. The acidic environment cleaves an amino acid sequence from pepsinogen, turning it into the active enzyme pepsin. This type of activation causes pepsin to only activate in the stomach lumen where it is needed.

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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