Cofactors & Enzyme Inhibitors

• Cofactor- non-protein molecule which must be present for an enzyme controlled reaction to occur.

  Some enzymes only work if a particular cofactor is present
• Cofactors remain unchanged or are recycled/regenerated at the end of a reaction
• Types of cofactors

  • Organic
  • Inorganic
  • Prosthetic Groups
• Inorganic Cofactors

  Usually ions

  • Stabilise enzyme structure
  • Makes the active site more complementary to the substrate

  
• Organic Cofactors

  Typically vitamins

  • Carry electrons/chemical groups between different molecules
  • Link reactions in sequence during metabolic processes
  • Some are permanently bound to the enzyme whilst some are only temporarily bound
• Prosthetic Groups

  Permanently attached to the enzyme - helps it function properly

  • Non-protein molecules-typically ions
  • Forms the final 3D shape
• Types of Enzyme Inhibition

  • Competitive Inhibition
  • Non-competitive Inhibition
• An enzyme Inhibitor is a substance/molecule that stops or slows down the rate of an enzyme-controlled reaction by affecting the enzyme molecule
• Inhibition can be reversible or non-reversible
• Competitive Inhibition

  Shape is complimentary to that of the enzyme's active site. Binds to the active site, not the substrate. Enzyme-substrate complexes form but no products are released.

  
• Non-competitive inhibition

  Non-competitive inhibitor molecules bind to the enzyme's allosteric site, changing the active sites shape, interfering with its tertiary structure which prevents the substrate from binding (the reaction isn't catalysed). There's no increase in the rate of reaction (on a graph).

  
• Metabolic Pathway

  A metabolic pathway is a series of enzyme-controlled biochemical reactions in where one substance is built up/broken down into another, e.g. respiration, photosynthesis

  The end product usually acts as a reversible inhibitor of the first enzyme in the chain which keeps a steady level of product in the cell.
• In a metabolic pathway, more end product=greater inhibition so less product is made. A reduction in the end product lessens the inhibition. This is called a negative feedback loop