The Mechanism of Enzyme Action

  • Created by: Freja
  • Created on: 08-04-21 17:22
View mindmap
  • The Mechanism of Enzyme Action
    • Lowers Activation Energy
      • Activation Energy-the energy required to initiate a reaction.
      • Enzymes reduce the amount of activation energy needed.
      • This speeds up the rate of reaction.
      • When a substrate binds to an enzyme's active site an enzyme-substrate complex is formed. The formation of enzyme-substrate complexes lower the activation energy.
        • If two substrate molecules need to be joined, attaching to the enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily.
        • If the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on the bonds in the substrate. This strain means the substrate molecule breaks up more easily.
    • Hypothesis
      • Lock and Key Hypothesis
        • The active site is complemen-tary in shape to the substrate.
        • Only an enzyme with a complemen-tary shape can bind to the substrate.
        • An enzyme-substrate complex is formed, the substrate then reacts and the product is formed in and enzyme-product complex.
        • The enzyme is unchanged after the reaction.
        • The substrate fits into the enzyme the same way a key fits into a lock.
      • Induced Fit Hypothesis
        • The substrate doesn't have to be the right shape to fit into the active site.
        • As the substrate binds, the active site changes shape slightly to fit the substrate more closely.
        • To begin with the interaction between the enzyme and a substrate is relatively weak, but the weak interactions rapidly cause changes in the tertiary structure.
        • An enzyme-substrate complex is formed, th substrate then reacts and the products are formed in an enzyme-product complex.
        • The enzyme is changed after the reaction.
        • This puts strain on the substrate molecule and can weaken the bonds, lowering the activation energy.
    • Specificity- each enzyme catalyses one biochemical reaction and there are thousands in any given cell.
      • Absolute specificity- enzyme only acts one type of substrate.
      • Group specificity-some enzymes act on a group of closely related enzymes.
    • Tertiary Structure
      • Active site is dependent on tertiary structure.
      • All enzymes are tertiary globular proteins.
    • Temperature Coefficient
      • The effect of a 10C rise in temperature has on the rate of reaction.
      • For enzyme controlled reactions, the reaction usually doubles with a 10C increase.
        • Therefore Q10=2
      • Q10 does not apply if the enzymes become denatured.
    • Enzyme Action
      • Molecules in a solution collide randomly. But for a reaction to happen, they need to collide in the right orientation.
      • The substrate molecule collides with the enzyme's active site and they bind, because they are comple-mentary in shape.
      • This forms an enzyme-substrate complex.
      • The substrate then reacts and forms an enzyme-product complex.
      • The product is then released and the enzyme can move onto other substrate molecules.


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Biology resources »