Proteins are chains of what molecular units?

Proteins are composed of long chains of amino acid molecules, which are organic compounds made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Each protein is formed through the process of protein synthesis, where amino acids are linked together by peptide bonds. The sequence and composition of these amino acids dictate the structure and function of the protein, making them essential for various biological functions, including building and repairing tissues, catalyzing metabolic reactions, and playing a role in immune responses.

The other molecular units listed—sugars, fatty acids, and nucleotides—serve entirely different roles in biological systems. Sugars are the building blocks of carbohydrates, fatty acids are components of lipids, and nucleotides are the monomers that make up nucleic acids like DNA and RNA. Each of these molecules contributes to cellular structure and function in specialized ways, but none relate to the formation of proteins as amino acids do.