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.

• 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.

• 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.

• 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.

• Transcription in Prokaryotes

  • The set of three nucleotides that codes for a single amino acid is known as a codon.
  • There are 64 codons in total, 61 that encode amino acids and 3 that code for chain termination.
  • For example, although codons GAA and GAG both specify glutamic acid (redundancy), neither of them specifies any other amino acid (no ambiguity).
  • The codons encoding one amino acid may differ in any of their three positions.
  • For example, the amino acid glutamic acid is specified by GAA and GAG codons (difference in the third position); the amino acid leucine is specified by UUA, UUG, CUU, CUC, CUA, CUG codons (difference in the first or third position); while the amino acid serine is specified by UCA, UCG, UCC, UCU, AGU, AGC (difference in the first, second or third position).

• Protein Structure

  • So, just one amino acid substitution can cause dramatic changes.
  • In the α-helix chain, the hydrogen bond forms between the oxygen atom in the polypeptide backbone carbonyl group in one amino acid and the hydrogen atom in the polypeptide backbone amino group of another amino acid that is four amino acids farther along the chain.
  • This holds the stretch of amino acids in a right-handed coil.
  • Every helical turn in an alpha helix has 3.6 amino acid residues.
  • The A chain of insulin is 21 amino acids long and the B chain is 30 amino acids long, and each sequence is unique to the insulin protein.

• The Protein Synthesis Machinery

  • The tRNA with this anticodon would be linked to the amino acid leucine.
  • This is called "activating" the amino acid.
  • After the correct amino acid covalently attached to the tRNA, it is released by the enzyme.
  • The tRNA is said to be charged with its cognate amino acid.
  • (the amino acid specified by its anticodon is a tRNA's cognate amino acid.)

• The Central Dogma: DNA Encodes RNA and RNA Encodes Protein

  • The genetic code is degenerate as there are 64 possible nucleotide triplets (43), which is far more than the number of amino acids .
  • These nucleotide triplets are called codons; they instruct the addition of a specific amino acid to a polypeptide chain.
  • Sixty-one of the codons encode twenty different amino acids.
  • Most of these amino acids can be encoded by more than one codon.
  • In addition to specifying the amino acid methionine, it also serves as the start codon to initiate translation.

• Processing of tRNAs and rRNAs

  • There are different tRNAs for the 21 different amino acids.
  • Most amino acids can be carried by more than one tRNA.
  • The cognate amino acid for a tRNA is the one specified by its anticodon.
  • Attaching this amino acid is called charging the tRNA.
  • The amino acid phenylalanine is attached to the other end of the tRNA.

• Food Requirements and Essential Nutrients

  • Amino acids are the building blocks of proteins and protein breakdown provides amino acids that are used for cellular function.
  • These amino acids are the "essential" amino acids.
  • These include vitamins, omega 3 fatty acids, and some amino acids.
  • There are 20 known amino acids.
  • Meats are the best source of amino acids, although some amino acids can also be obtained from vegetables and grains.