Which of the following classes of biological molecules includes enzymes?
A. Lipids
B. Vitamins
C. Carbohydrates
D. Proteins
Enzymes are a type of protein that catalyze chemical reactions in the body. Proteins are one of the four main classes of biological molecules, along with lipids, carbohydrates, and nucleic acids.
The other options are not classes of biological molecules that include enzymes. Lipids are a class of molecules that includes fats and oils, vitamins are organic compounds that are essential for normal growth and nutrition, and carbohydrates are a class of molecules that includes sugars and starches.
Therefore, the Correct Answer is D.