GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Enzyme Identification

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

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Example Questions

Example Question #7 : Enzyme Principles

Which of the following changes cannot be accomplished by an enzyme in a chemical reaction?

Possible Answers:

Change in activation energy

Change in reverse reaction rate

Change in forward reaction rate

Change in enthalpy

Correct answer:

Change in enthalpy

Explanation:

An enzme is a biological catalyst that increases the rate of a reaction. This is accomplished by lowering the activation energy necessary to start the reaction. The equilibrium of the reaction, however, is not affected. This means that enthalpy and entropy are not affected by an enzyme's presence.

Example Question #8 : Enzyme Principles

The class of enzymes that break bonds by forming a new double bond or ring structure (rather than by hydrolysis or oxidation) is best characterized as which of the following?

Possible Answers:

Isomerases

Transferases

Lyases

Ligases

Kinases

Correct answer:

Lyases

Explanation:

The correct answer is lyases. This class of enzymes only requires one substrate for the forward reaction.

Ligases catalyze the formation of a bond between two molecules, isomerases rearrange the atoms of a molecule, kinases phosphorylate molecules, and transferases transfer or join functional groups from one molecule to another. 

Example Question #9 : Enzyme Principles

The third step of glycolysis converts fructose-6-phosphate to fructose-1,6-bisphosphate. What type of enzyme mediates this?

Possible Answers:

A phosphatase

A reductase

A kinase

A polymerase

An isomerase

Correct answer:

A kinase

Explanation:

Kinases are enzyme that catalyze the transfer of a phosphate group from ATP to a substrate molecule. The phosphorylation of fructose-6-phosphate to fructose-1,6-phosphate is mediated by a kinase phosphofructokinase.

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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