Unit 2 Section 3.3 Cofactors and Inhibitors

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  • Cofactors and Inhibitors
    • Cofactors and Coenzymes
      • Inorganic cofactors
        • Some cofactors are inorganic molecules. They work by helping the enzyme and substrate to bind together
          • They dont directly participate inn the reaction so aren't used up or changed in any way.
            • EG.. Manganese ions are cofactors found in hydrolase
      • Organic Cofactors
        • Some cofactors are organic molecules - these are called coenzymes.
          • They participate in the reaction and are changed by it
            • They often act as carriers, moving chemical groups between different enzymes. They're continually recycled during this process
    • Enzyme Inhibitors
      • Enzyme activity can be prevented by enzyme inhibitors - molecules that bind to the enzyme that they inhibit. inhibition can be conpetitive or non-competetive
      • Competetive Inhibitors
        • Competetive Inhibitor molecules have a similar shape to that of the substrate molecules. They compete with the substrate molecules
          • They compete with the substrate molecules to bind to the active site, but no reaction takes place
            • Instead they block the active site, so no substrate molecules can fit in it
              • How much the enzyme is inhibited depends on the relative concentrations of the inhibitor and substrate. if there's a high concentration of the inhibitor, it'll take up nearly all the active sites and hardly any of the substrate will get to the enzyme
      • Non Competeive Inhibitors
        • Non - competetive inhibitor molecules. bind to the enzyme away from its active site
          • This causes the active site to change shape so the substrate molecules can no longer bind to it
            • They Dont compete with the substrate molecules to bind to the active site because they are a different shape
              • icreasing the concentration of the substrate wont make any difference 0 enyme activity will bestill be inhibited
      • Reversible and Non Reversible Inhibition
        • Inhibitors can be reversible or non reversible
        • Which one they are depends on the strength of the bonds between the enzyme and the inhibitor
          • if they're strong, covalent bonds, the inhibitor can't be removed easily and the inhibition is irreversible
          • if they're wealker hydrogen bonds or weak ionic bonds the inhibitor can be removed and the inhibition is reversibe
    • Metabolic Poisons
      • metabolic poisons interfere with metabolic reactions  causing damage illness or death
        • they're often enzyme inhibitors in the exam you might be asked to desbribe the action of one named poison
          • EG... Cynaide is a non competetive inhibitor of cytochrome c ozxidase, an enzyme  that catalyses respiration reactions. cells that cant respire die
    • Drugs
      • Some medical drugs are enzyme inhibitors
        • for example. some antiviral drugs eg reverse transcriptase inhibitors are a class of antiviral developed to treat HIV, they work by inhibiting the enzyme reverse transcriptase, which catalyses the replication of viral DNA


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