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MCAT Question A Day - 8/8/13 - Answer!

Magnesium and calcium are essential to the proper functioning of numerous enzymes in a variety of reactions. The term that best describes their role is

A.  essential amino acids.
B.  coenzymes.
C.  cofactors.
D.  catalysts.

The correct answer is (C). Molecules that are needed to assist enzymes are usually considered either cofactors or coenzymes. Since calcium and magnesium are inorganic, they are referred to as cofactors. Organic molecules, such as certain vitamins, would be referred to as coenzymes. Only the enzymes themselves are considered catalysts.

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