Amino acids are organic compounds containing both an amino group (-NH2) and a carboxylic acid group (-COOH) attached to the same carbon atom (the α-carbon), with a variable side chain R. They serve as the fundamental building blocks of proteins and peptides in all living organisms. There are 20 standard proteinogenic amino acids, classified as essential or non-essential based on human dietary requirements. They exhibit zwitterionic behavior in solution due to their amphoteric nature, with isoelectric points varying by side chain. Amino acids participate in metabolism, neurotransmission, and biosynthesis pathways. Physical properties such as melting points (typically 200-300°C with decomposition) and solubilities differ significantly among individual members like glycine (highly water-soluble) versus leucine (less soluble). They are generally stable solids at room temperature and play critical roles in food chemistry, flavor enhancement, and nutritional science.