Proteins are large biomolecules consisting of one or more long chains of amino acid residues linked by peptide bonds. They perform essential functions in living organisms including catalysis, structural support, transport, and signaling. In food science, proteins from sources like meat, eggs, dairy, and plants provide nutrition and affect texture through denaturation, gelation, and emulsification. Chemical composition varies but typically includes C, H, O, N, and sometimes S. Properties such as solubility and stability depend on sequence, folding, pH, temperature, and ionic strength. Proteins denature rather than boil or melt at defined points and are biodegradable.