2.3.3 - Factors affecting enzyme activity - Part 2


Cofactors and coenzymes:

  • Some enzymes will only work if there is another non-protein substance bound to them. These are called cofactors. Some cofactors are inorganic molecules. They work by helping the enzyme and substrate to bind together. They don't directly participate in the reaction so aren't used up or changed in any way. Some cofactors are organic molecules- these are called coenzymes. They participate in the reaction and are changed by it (like a second substrate). They often act as carriers, moving chemical groups between different enzymes. They are continually recycled in this process. 

Enzyme inhibitors:

  • Competitive- Have a similar shape to that of 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. How much the enzyme is inhibited depends on the relative concentrations of the inhibitor and substrate. If there is a high concentration of inhibitor, it will take up nearly all of the active sites and hardly any substrate


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