What are proteins made up of?

Proteins are composed of chains of amino acids, which are organic compounds containing amine (-NH2) and carboxyl (-COOH) functional groups, along with a unique side chain for each amino acid. The sequence and arrangement of these amino acids determine the structure and function of the protein. There are 20 different amino acids that can be combined in various ways to create a vast diversity of proteins, essential for many biological functions such as catalyzing metabolic reactions, replicating DNA, responding to stimuli, and transporting molecules.

The other options represent different types of biological macromolecules. Sugars and fats are building blocks of carbohydrates and lipids, respectively. Carbohydrates are primarily energy sources and structural components, not directly involved in protein synthesis. Nucleotides are the building blocks of nucleic acids, such as DNA and RNA, which play important roles in genetic information storage and transfer but are not components of proteins themselves.