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 #3 : Enzymes
Which of the following changes cannot be accomplished by an enzyme in a chemical reaction?
Change in enthalpy
Change in activation energy
Change in reverse reaction rate
Change in forward reaction rate
Change in enthalpy
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 #7 : Enzymes
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?
Kinases
Ligases
Lyases
Transferases
Isomerases
Lyases
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 #8 : Enzymes
The third step of glycolysis converts fructose-6-phosphate to fructose-1,6-bisphosphate. What type of enzyme mediates this?
A kinase
An isomerase
A phosphatase
A reductase
A polymerase
A kinase
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.
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All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
