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  • Proteins
    • Function
      • Structural
        • Main component of body tissues like muscles, skin, ligaments and hair
      • Catalytic
        • all enzymes are proteins, catalysing many biochemical reactions
      • Signaling
        • Many hormones and receptors are proteins
      • Immunological
        • all antibodies are proteins
    • Monomer = amino acids
    • Dipeptides
      • two amino acids joined together
      • Joined by a peptide bond
    • Polypeptides
      • many amino acids joined to form a chain
      • Joined by peptide bonds
    • Levels of protein structure
      • Primary    (long chain)
        • number, sequence and order of amino acids in the polypeptide chain (governed by order of DNA bases)
        • Bonds = peptide bonds
        • chain constructed at ribosome
      • Secondary
        • Folding of the polypeptide chain into alpha helixes and beta pleated sheets
        • Bonds = peptide and hydrogen
      • Tertiary
        • Interaction of the R groups folding the chain into a 3D structure
        • Bonds = peptide, hydrogen, Di-sulphide, hydrophobic, ionic and VDW
      • Quaternary
        • interaction of more than one polypeptide chain
        • Bonds = peptide, hydrogen, Di-sulphide, hydrophobic, ionic and VDW
    • Types of protein structure
      • Fibrous 'elongated'
        • formed from parallel  polypeptide chains held together by cross links
        • Form long rope like fibres, with high tensile strength and are generally insoluble in water
        • E.g. Collagen + Keratin
      • Globular
        • Usually have a spherical shape caused by tightly folded polypeptide chains
        • Chains are usually folded so that hydrophobic groups are on the inside + hydrophobic on the outside
        • Many soluble in water
        • E.g haemoglobin and all enzymes


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