Amino Acids


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•  There are 20 different amino acids in polypeptides synthesised on ribosomes

Proteins are comprised of long chains of recurring monomers called amino acids

Amino acids all share a common basic structure, with a central carbon atom bound to:

  • An amine group (NH2)
  • A carboxylic acid group (COOH)
  • A hydrogen atom (H)
  • A variable side chain (R)

Structure of a Generalised Amino Acid

amino acid

There are 20 different amino acids which are universal to all living organisms

  • A further two – selenocysteine and pyrrolysine – are modified variants found only in certain organisms

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•  Amino acids can be linked together in any sequence giving a huge range of possible polypeptides

Amino acids are joined together on the ribosome to form long chains called polypeptides, which make up proteins

Each type of amino acid differs in the composition of the variable side chain

These side chains will have distinct chemical properties (e.g. charged, non-polar, etc.) and hence cause the protein to fold and function differently according to its specific position within the polypeptide chain

As most natural polypeptide chains contain between 50 – 2000 amino acid residues, organisms are capable of producing a huge range of possible polypeptides

The 20 Universal Amino Acids

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  Click on the diagram to swap between chemical structure and molecular representations