As Biology - Biological Molecules - Proteins

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Chains of amino acids

  • A dipeptide is formed when two amino acids join together
  • A polypeptide is formed when more than two amino acids join together
  • Proteins are made up of one or more polypeptides

Different variable groups

  • All amino acids have the same general structure
    - a carboxyl group (-COOH) and an amino group (-NH2) attached to a carbon atom
  • The difference between different amino acids is the variable group they contain

Peptide bonds

  • Amino acids are linked together by peptide bonds to form dipeptides and polypeptides
  • It's a condensation reaction, which means a molecule of water is released during the reaction
  • The reverse of this reaction adds a molecule of water to break the peptide bond - this is called a hydrolysis reaction

Four structural levels

  • Primary structure: this is the sequence of amino acids in the polypeptide chain
  • Secondary structure: the polypeptide chain doesn't remain flat and straight. Hydrogen bonds form between the amino acids in the chain. This makes it automatically coil into an alpha helix or fold into a beta pleated sheet
  • Tertiary structure: the coiled or folded chain of amino acids is often coiled and folded further. More bonds form between different parts of the polypeptide chain. For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure
  • Quaternary structure: some proteins are made from several different polypeptide chains held together by bonds. The…


Toby Bonnett


Great notes buddy!



thanks for the notes..hats off

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