Epithelial cells form a layer in which an apical surface is exposed to the external environment and to other forms of stress in ducts in specialized organs. As such, epithelial cells require robust ...

Essential amino acids are organic compounds your body can’t produce on its own. The nine essential amino acids—histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, ...

Serotonin is a neurotransmitter and hormone that helps regulate mood, sleep, digestion, blood clotting, and sex drive. Your body makes it from tryptophan, an amino acid found in meat, dairy, eggs, and ...