Proteins

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  • Proteins
    • Amino Acids
      • every amino acid has a central carbon atom
      • polypeptides combine to form proteins
      • amino group
      • are the basic monomers that make polymers
      • carboxyl group
      • R group
      • hydrogen atom
    • Secondary structure
      • this causes the polypeptide chain to form a 3-D shape
      • the two groups form weak bonds called hydrogen bonds
      • the  -NH group is positive and the -C=O group is negative
      • the chain forms an alpha helix
    • Polypeptides
      • the primary structure determines the ultimate shape of a protein
      • this sequence of amino acids form the primary structure of any protein
      • a change in a single amino acid can lead to a change in function
      • the resulting chain is called a polypeptide
      • a change in shape means it will function less well
      • many amino acids joining together is called polymerisation
      • proteins are commonly made up of a number of polypeptide chains
    • Peptide Bonds
      • formed from a condensation reaction
      • two amino acids are joined by peptide bonds
      • combines an -OH from the carboxyl group and a -H from the amino group
      • the bond can be broken by hydrolysis
    • Tertiary Structure
      • the alpha helices can be twisted and folded
      • ionic bonds = easily broken
      • disulfide bonds = fairly strong
      • 3-D shape makes each protein distinct allowing it to function
      • hydrogen bonds = easily broken
    • Quaternary Structure
      • contain a number of individual polypeptide chains
      • they may also contain prosthetic groups which are non-protein
  • Biuret test for proteins, add sodium hydroxide and copper sulfate at room temperature. If the solution turns purple, proteins are present.

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