Types of proteins - biochemistry

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  • Created by: HeHeHe24
  • Created on: 06-12-19 16:11
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  • Types of proteins
    • Globular Proteins
      • irregular primary structure
      • insoluble
      • spherical shape
      • compact
      • metabolic role
      • Haemoglobin
        • Carries oxygen around the body
        • Iron ion haem group to reversibly combine with oxygen
        • quaternary protein
        • tertiary structure
        • 4 polypeptides: 2 alpha & 2 beta subunits
        • pick up oxygen due to haem group and release when needed
          • has different affinities for oxygen when different levels of carbon dioxide is present
            • high carbon dioxide - low affinity - release
            • low carbon dioxide - high affinity - take in
      • Catalase
        • catalyses reaction to convert hydrogen peroxide into water and oxygen
        • enzyme
          • increases rate of reaction
            • lower the activation energy
        • quaternary protein
        • Haem group (Iron (II))
          • allows catalase to interact with hydrogen peroxide
          • speeds up the breakdown
        • ensures hydrogen peroxide doesn't accumulate
    • Fibrous Proteins
      • regular primary structure
      • soluble
      • long straight chained rope like structures
      • structural role
      • Keratin
        • hair, skin and nails
        • large proportion of cysteine
          • lots of disulfide linkages
          • strong, inflexible and insoluble
        • hair has fewer disulfide linkages than nails
          • more flexible
        • unpleasant smell when burned
          • lots of sulfur released
      • Elastin
        • elastic fibres
        • blood vessel walls
        • alveoli in lungs
        • provide flexibility
          • stretch and recoil
        • quaternary protein
          • made up of stretchy molecules - tropoelastin
            • hydrophobic and lysine rich areas
            • joined by cross linked covalent bonds
          • insoluble
        • is strong to withstand high pressures
      • Collagen
        • connective tissue
          • skin
          • tendons
          • ligaments
          • nervous system
        • 3 polypeptides wound into a long rope like structure
          • closely packed triple helix
          • many hydrogen bonds
            • form long quaternary proteins
            • staggered ends
              • forms tropocollagen that cross link to form strong fibres
        • high proportions of proline and hydroxylproline
          • repel each other
            • increased stability
        • high tensile strength
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