Proteins are large biomolecules consisting of one or more long chains of amino acid residues linked by peptide bonds. They are essential macromolecules present in all living organisms and perform diverse functions such as enzymatic catalysis, structural support, transport, signaling, and immune response. In food science and nutrition, proteins from sources like meat, eggs, dairy, legumes, and grains provide essential amino acids, contribute to texture, emulsification, and flavor development. General chemical properties include a repeating backbone of -[NH-CHR-CO]- units with variable side chains (R groups) that determine hydrophobicity, charge, and solubility. Proteins denature under heat, pH extremes, or mechanical stress rather than exhibiting defined melting or boiling points. Solubility in water depends on the specific protein, pH, ionic strength, and temperature, with many food proteins showing moderate solubility in aqueous media.