Amino acids are organic molecules that serve as the fundamental building blocks of proteins, which are essential for all living organisms
. Chemically, each amino acid contains both an amino group (-NH2) and a carboxylic acid group (-COOH), along with a unique side chain (R group) that determines its specific properties
. There are 20 standard amino acids that the human body uses to build proteins. These amino acids link together in chains called polypeptides, which fold into functional proteins responsible for various biological roles, including muscle building, tissue repair, hormone production, and immune function
. Amino acids are classified into three main groups based on the body's ability to produce them:
- Essential amino acids: These cannot be synthesized by the body and must be obtained through diet. There are nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine
- Nonessential amino acids: The body can produce these amino acids even if they are not obtained from food. Examples include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine
- Conditionally essential amino acids: These are usually nonessential but become essential under certain conditions such as illness, stress, or pregnancy. Examples include arginine, cysteine, glutamine, tyrosine, glycine, proline, and serine
Beyond their role in protein synthesis, some amino acids serve as precursors for important molecules like hormones and neurotransmitters. For example, tyrosine is a precursor for thyroid hormones and neurotransmitters such as epinephrine and norepinephrine
. In summary, amino acids are vital organic compounds that build proteins and support numerous physiological functions, with a subset being essential nutrients that must be obtained through diet
