Question

what is an enzyme?
a. a protein that catalyzes (speeds up) the rate of a chemical reaction
b. a carbohydrate that catalyzes (speeds up) the rate of a chemical reaction
c. a protein that allows muscles to contract
d. a lipid that allows muscles to contract and that slows down chemical reactions

Explanation:

Enzymes are biological catalysts, and most enzymes are proteins. They speed up chemical reactions. Option A states "A protein that catalyzes (speeds up) the rate of a chemical reaction", which matches the definition of an enzyme. Option B is incorrect because enzymes are not carbohydrates. Options C and D describe proteins or lipids involved in muscle contraction or slowing chemical reactions, not the function of enzymes.

Answer:

A. A protein that catalyzes (speeds up) the rate of a chemical reaction