Amino acids are organic compounds containing both an amino group and a carboxylic acid group, serving as the fundamental building blocks of proteins in all living organisms. There are 20 standard amino acids used in protein synthesis, each differing in their side chain (R group), which determines their unique chemical properties, polarity, and biological functions. They play critical roles in metabolism, neurotransmission, and as precursors for hormones and nucleotides. Most amino acids are chiral and exist in L-form in nature. They are highly soluble in water due to their zwitterionic nature at physiological pH. In food science, amino acids contribute to flavor (e.g., umami from glutamic acid) and are used as supplements or additives. Properties vary widely; for example, glycine is the simplest with no chiral center, while others like leucine are hydrophobic.