Final answer:
Proteins are the category of large molecules that perform important functions inside living things. They are one of the most abundant organic molecules in living systems and have diverse functions including enzymes and hormones.
Step-by-step explanation:
The category of large molecules that perform important functions inside living things is proteins. There are four major biological macromolecule classes, namely carbohydrates, lipids, proteins, and nucleic acids. Proteins are one of the most abundant organic molecules in living systems and have a diverse range of functions. They can serve as enzymes, hormones, contractile fibers, and more.