Biological Molecules- protiens and enzymes

  • Created by: gsemma
  • Created on: 07-10-18 10:29
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  • Proteins
    • amino acids
      • building block of all proteins
        • joined by peptide bonds
          • 2= dipeptide
          • many= polypeptide
          • covalent bond between carboxyl group and hydroxyl group of 2 AA and release oxygen
          • broken apart by hydrolysis
            • enzymes catalyse this
              • formed by condensation reactions
          • formed by condensation reactions
      • general structure (draw)
      • R= variant. 20 different ones
        • simplest is H making Glycine
    • Enzymes
      • structure
        • globular proteins
        • specific active site to the substrate
          • tertiary structure determines this
          • lock and key model
            • active site is ridged where substrate fits exactly
            • forms enzyme substrate complexes
              • active site is ridged where substrate fits exactly
              • products separate form enzyme and the enzyme is unchanged
        • induced fit model
          • active site is not ridged- can slightly change
            • an enzyme substrate complex is formed when the enzyme forms around the substrate.
              • when the products leave, the enzyme returns to original shape
      • activation energy
        • amount of energy needed for a reaction to occur
          • enzymes provide an alternative pathway and reduce the activation energy
            • this speeds up reactions and allows them to occur at lower temperatures.
      • Factors affecting enzyme function.
        • temperature
          • increase rate as there is more kinetic energy meaning the enzyme substrate complexes are formed faster and are more likely to happen
            • if the temp gets to high the enzyme will denature
        • substrate concentration
          • higher conc leads to increased rate due to a greater chance of ESC being formed.
            • it will reach a saturation point where no more ESC will be formed as all enzymes are used up
              • once all the substrate has been used up, the reaction will top.
        • pH
          • at optimum- fastest rate. below will be slower and above will cause enzymes to denature.
        • Enzyme conc
          • same as substrate conc and limiting factor is amount of substrate
      • enzyme inhibitors
        • competitive
          • their shape is complimentary t the active site of the enzyme where they bind so no reactions can take place
          • If one forms a covalent  bond with the enzyme the effect is irreversible
            • if a hydrogen bond if formed the effect is reversible because it is weaker.
        • non-competitive
          • bind to enzyme's allosteric site and causes it to change shape so nor reactions can take place
          • If one forms a covalent  bond with the enzyme the effect is irreversible
            • if a hydrogen bond if formed the effect is reversible because it is weaker.
    • Different levels of structure
      • primary structure
        • sequence of amino acids held by peptide bonds. each protein has own sequance
      • secondary structure
        • interaction between amino acids- beta plated or alpha helices
          • determined by hydrogen bonding between carboxyl and amino groups
      • tertiary structure
        • further coiling to give 3D shape of polypeptide
          • held by H bonds, ionic bonds, disulphur bonds and hydrophobic and hydrophilic interactions.
            • ionic- attraction between positive and negative R groups
            • disulphide- 2 sulphurs called cysteine bonds together
      • Quaternary structure
        • how several polypeptide chains
          • determined by tertiary structure so all bonds contribute
    • test
      • biuret
        • add sodium hydroxide to sample to make it alkaline
          • add copper sulphate to sample
            • blue to purple when positive

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