大象传媒

Enzymes and digestion

Enzyme action

  • Enzymes are proteins that act as biological catalysts - this means they speed up reactions without being used up.
  • An works on the , forming products.
  • An enzyme鈥檚 and its substrate are in shape.
  • An enzyme will only work on one substrate - it is substrate specific.
  • Enzymes and substrates collide to form enzyme-substrate complexes.
  • The substrates are broken down (or in some cases built up).
  • The products are released.
  • The enzyme is free to act again.
  • This theory is known as the 鈥榣ock and key model鈥.
  • It explains why each enzyme will only work on one substrate.
  • For example, the active site of is only complementary to starch and will therefore only break down starch, not protein or fat.
EnzymeSubstrateProduct
CarbohydraseCarbohydrate Simple sugar, glucose
AmylaseStarch Simple sugar, glucose
ProteaseProtein Amino acid
LipaseFat (lipid)Glycerol and fatty acids
EnzymeCarbohydrase
SubstrateCarbohydrate
ProductSimple sugar, glucose
EnzymeAmylase
SubstrateStarch
ProductSimple sugar, glucose
EnzymeProtease
SubstrateProtein
ProductAmino acid
EnzymeLipase
SubstrateFat (lipid)
ProductGlycerol and fatty acids

Inhibitors

Inhibitors are molecules that partially fit into an enzyme鈥檚 active site but are not broken down.

They inhibit the reaction.

As long as they are in the active site the substrate cannot enter to be broken down, thus reducing the rate of reaction.

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