An active site of an enzyme is
A) the part of the enzyme that binds ATP.
B) a sequence of DNA nucleotides that encodes a protein molecule.
C) the part of a substrate that combines with an enzyme.
D) the part of an enzyme that combines with a substrate.

Question

Quizplus · Accepted Answer

The active site of an enzyme is the specific region where the enzyme binds to the substrate to form an enzyme-substrate complex, leading to a biochemical reaction. Therefore, the best choice is D, which states that the active site of an enzyme is the part of the enzyme that combines with a substrate. The other choices are incorrect because:

A) ATP is a molecule that is bound by some enzymes, but not all enzymes. Therefore, this choice is too narrow in its definition of the active site of an enzyme.
B) This choice describes a sequence of DNA nucleotides that encodes a protein molecule, which is different from the active site of an enzyme. Therefore, this choice is unrelated to the active site of an enzyme.
C) This choice describes the part of a substrate that combines with an enzyme, which is different from the active site of an enzyme. Therefore, this choice is also unrelated to the active site of an enzyme.

An Active Site of an Enzyme Is