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Biological Environment > Amino Acids
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Like all other proteins, enzymes are built from smaller molecules called amino acids. Amino acids, as their name suggest, contain an amino group and an acid group. In the diagram we show the simplest of all amino acid, glycine, with its amino and acid groups.

Different amino acids have a different set of atoms fixed to them. In glycine there is just one atom in this group, a single hydrogen atom, marked H in the diagram.

More than 100 amino acids occur in bacteria and plants, but only about 20 are commonly found in most animal proteins:

  • alanine
  • arginine
  • asparagine
  • aspartic acid
  • cysteine
  • glutamic acid
  • glutamine
  • glycine
  • histidine
  • hydroxyproline
  • isoleucine
  • leucine
  • lysine
  • methionine
  • phenylalanine
  • proline
  • serine
  • threonine
  • tryptophan
  • tyrosine
  • valine
 
Here is a more complex amino acid, tyrosine. At the bottom of the molecule you can still see the amino and acid groups, but instead of the single hydrogen atom which sits on top of glycine, a much larger group of atoms sits on top of tyrosine.

Life uses about 20 different amino acids, each with a different set of atoms attached to the basic amino and acid groups.

 

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