amino acid

(noun)

Any of the twenty naturally occurring α-amino acids (having the amino, and carboxylic acid groups on the same carbon atom), and a variety of side chains, that combine, via peptide bonds, to form proteins.

Related Terms

Examples of amino acid in the following topics:

  • Proteins: Sources, Uses in the Body, and Dietary Requirements

    • Most microorganisms and plants can biosynthesize all 20 standard amino acids , while animals (including humans) must obtain some of the amino acids from the diet.
    • The amino acids that an organism cannot synthesize on its own are referred to as essential amino acids.
    • Key enzymes that synthesize certain amino acids are not present in animals.
    • In animals, amino acids are obtained through the consumption of foods containing protein .
    • Amino acids are also an important dietary source of nitrogen.

  • Types of Neurotransmitters by Function

    • The major types of neurotransmitters include: acetylcholine, biogenic amines and amino acids.  
    • Dopamine and NE are synthesized from amino acid tyrosine.
    • Histamine is synthesized from amino acid ___.
    • Glutamate and gamma - aminobutyric acid (GABA) are amino acid based neurotransmitters.
    • Neuropeptides such as Substance P and Endorphins are strings of amino acids that are important in the mediation of pain signals.

  • Phenylketonuria (PKU)

    • PAH enzyme is necessary for the metabolism of the amino acid phenylalanine (Phe) to the amino acid tyrosine.
    • Phenylalanine is a large, neutral amino acid (LNAA).
    • LNAAs compete for transport across the blood–brain barrier (BBB) via the large neutral amino acid transporter (LNAAT).
    • However, as these amino acids are necessary for protein and neurotransmitter synthesis, Phe buildup hinders the development of the brain, causing mental retardation.
    • The mainstream treatment for classic PKU patients is a strict PHE-restricted diet supplemented by a medical formula containing amino acids and other nutrients.

  • Absorption of Monosaccharides, Amino Acids, Dipeptides, Tripeptides, Lipids, Electrolytes, Vitamins, and Water

    • Glucose, amino acids, fats, and vitamins are absorbed in the small intestine via the action of hormones and electrolytes.
    • Proteins are degraded into small peptides and amino acids before absorption.
    • Carboxypeptidase, which is a pancreatic brush border enzyme, splits one amino acid at a time.
    • Aminopeptidase and dipeptidase free the end amino acid products.
    • Lipids (fats) are degraded into fatty acids and glycerol.

  • Chemistry of Hormones

    • Peptide hormones consist of chains of amino acids (example vasopressin) or longer chains of amino acids (example insulin) .
    • Lipid- and phospholipid-derived hormones are produced from lipids such as linoleic acid and arachidonic acid.
    • Monoamine hormones are derived from aromatic amino acids like phenylalanine, tyrosine and tryptophan.

  • Mechanisms of Chemical Digestion

    • ., polysaccharides, proteins, fats, nucleic acids) to smaller ones (i.e., monosaccharides, amino acids, fatty acids, nucleotides) .
    • The endopeptidases cleave the polypeptide at the interior peptide bonds, while the exopeptidases cleave the terminal amino acid.
    • Exopeptidases are further subclassified into aminopeptidases - which cleave off the terminal amino acid at the amine end of the chain, and carboxypeptidases which cleave off the terminal amino acid at the carboxyl end of the chain.
    • Stomach pepsin cleaves interior bonds of the amino acids, and is particularly important for its ability to digest collagen.
    • Fats are digested by lipases which hydrolyze the glycerol-fatty acid bonds.

  • Absorptive State

    • This main product of fat digestion is first broken down to fatty acids and glycerol through hydrolysis using lipoprotein lipase.
    • The liver deaminates amino acids to keto acids to be used in the Kreb's cycle in order to generate energy in the form of ATP.

  • Digestive Processes of the Small Intestine

    • Proteins are degraded into small peptides and amino acids before absorption.
    • Carboxypeptidase, a pancreatic brush border enzyme, splits one amino acid at a time.
    • Aminopeptidase and dipeptidase free the end amino acid products.
    • Lipids (fats) are degraded into fatty acids and glycerol.
    • Pancreatic lipase breaks down triglycerides into free fatty acids and monoglycerides.

  • Gastric Phase

    • The gastric phase is a period in which swallowed food and semidigested protein (peptides and amino acids) activate gastric activity.
    • All three of these stimulate parietal cells to secrete hydrochloric acid and intrinsic factor.
    • As dietary protein is digested, it breaks down into smaller peptides and amino acids, which directly stimulate the G cells to secrete even more gastrin: a positive feedback loop that accelerates protein digestion.
    • Small peptides also buffer stomach acid so the pH does not fall excessively low.
    • Below pH of two, stomach acid inhibits the parietal cells and G cells: a negative feedback loop that winds down the gastric phase as the need for pepsin and HCl declines.

  • Carbohydrates: Sources, Uses in the Body, and Dietary Requirements

    • Humans can synthesize some glucose (in a set of processes known as "gluconeogenesis") from specific amino acids or from the glycerol backbone in triglycerides and, in some cases, from fatty acids.
    • In the case of protein, this is somewhat misleading as only some amino acids are able to undergo conversion into useful energy forms.