amino acid

Examples of amino acid in the following topics:

• Amino Acids

  • An amino acid contains an amino group, a carboxyl group, and an R group, and it combines with other amino acids to form polypeptide chains.
  • The name "amino acid" is derived from the amino group and carboxyl-acid-group in their basic structure.
  • Each amino acid is attached to another amino acid by a covalent bond, known as a peptide bond.
  • When two amino acids are covalently attached by a peptide bond, the carboxyl group of one amino acid and the amino group of the incoming amino acid combine and release a molecule of water.
  • The carboxyl group of one amino acid is linked to the amino group of the incoming amino acid.

• The Incorporation of Nonstandard Amino Acids

  • Aside from the 22 standard amino acids, there are many other amino acids that are called non-proteinogenic or non-standard.
  • Also, most nascent polypeptides start with the amino acid methionine because the "start" codon on mRNA also codes for this amino acid.
  • Aside from the 22 standard amino acids, there are many other amino acids that are called non-proteinogenic or non-standard .
  • Some nonstandard amino acids are not found in proteins.
  • Nonstandard amino acids often occur as intermediates in the metabolic pathways for standard amino acids.

• Connecting Proteins to Glucose Metabolism

  • However, if there are excess amino acids, or if the body is in a state of starvation, some amino acids will be shunted into the pathways of glucose catabolism.
  • Each amino acid must have its amino group removed (deamination) prior to the carbon chain's entry into these pathways.
  • When the amino group is removed from an amino acid, it is converted into ammonia through the urea cycle.
  • The remaining atoms of the amino acid result in a keto acid: a carbon chain with one ketone and one carboxylic acid group.
  • Several amino acids can enter glucose catabolism at multiple locations.

• Amino Acid Synthesis

  • These polymers are linear and unbranched, with each amino acid within the chain attached to two neighboring amino acids.
  • Twenty-two amino acids are naturally incorporated into polypeptides and are called proteinogenic or natural amino acids.
  • Amino acid synthesis depends on the formation of the appropriate alpha-keto acid, which is then transaminated to form an amino acid.
  • Aside from the 22 standard amino acids, there are many other amino acids that are called non-proteinogenic or non-standard.
  • Nonstandard amino acids often occur as intermediates in the metabolic pathways for standard amino acids — for example, ornithine and citrulline occur in the urea cycle, part of amino acid catabolism.

• Lipid-Derived, Amino Acid-Derived, and Peptide Hormones

  • All hormones in the human body can be divided into lipid-derived, amino acid-derived, and peptide hormones.
  • The amino acid-derived hormones are relatively small molecules derived from the amino acids tyrosine and tryptophan .
  • If a hormone is amino acid-derived, its chemical name will end in "-ine".
  • The structure of peptide hormones is that of a polypeptide chain (chain of amino acids).
  • Amino acid-derived and polypeptide hormones are water-soluble and insoluble in lipids.

• Vitamins and Amino Acids

  • Microorganisms and plants can synthesize many uncommon amino acids and vitamins.
  • Amino acids are biologically important organic compounds made from amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid.
  • The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen.
  • About 500 amino acids are known which can be classified in many ways.
  • Microorganisms and plants can synthesize many uncommon amino acids.

• Peptide Bonding between Amino Acids

  • The peptide bond is an amide bond which links amino acids together to form proteins.
  • A peptides is a molecule composed of two or more amino acids.
  • The bond that holds together the two amino acids is a peptide bond, or a covalent chemical bond between two compounds (in this case, two amino acids).
  • The peptide bond (circled) links two amino acids together.
  • Identify the amino acids that were combined to create a peptide.

• 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.

• Synthesis of Amino Acids

  • Nevertheless, more complex procedures that give good yields of pure compounds are often chosen for amino acid synthesis.
  • The alpha-amino nitrile formed in this way can then be hydrolyzed to an amino acid by either acid or base catalysis.
  • This is illustrated for a generic amino acid in the following diagram.
  • The racemic amino acid is first converted to a benzamide derivative to remove the basic character of the amino group.
  • Of course, the same procedure could be used to obtain the (-)-enantiomer of the amino acid.

• α-Amino Acids

  • Some common features of these amino acids should be noted.
  • The simple amino acid alanine is the last entry.
  • This behavior is general for simple (difunctional) amino acids.
  • Arginine is a basic amino acid.
  • Some amino acids have additional acidic or basic functions in their side chains.