Nearly all animals rely on three main classes of molecule as sources of energy and building blocks for growth and development. They are:

Question

Quizplus · Accepted Answer

Proteins, fats, and carbohydrates are the three main classes of molecules that animals rely on for energy and building blocks. Nucleic acids and amino acids are important as well, but they are not considered as one of the main classes of molecules that animals rely on. Sugars are a type of carbohydrate, so they are included in the third class of molecules in this answer.

Nearly All Animals Rely on Three Main Classes of Molecule