Activation Energy

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•  Enzymes lower the activation energy of the chemical reactions that they catalyse

Every chemical reaction requires a certain amount of energy in order to proceed – this is the activation energy (EA)

  • Enzymes speed up the rate of a biochemical reaction by lowering the activation energy
  • When an enzyme binds to a substrate it stresses and destabilises the bonds in the substrate
  • This reduces the overall energy level of the substrate’s transitionary state, meaning less energy is needed to convert it into a product and the reaction proceeds at a faster rate

Activation Energy

activation energy

Types of Enzymatic Reactions

If the reactants contain more energy than the products, the free energy is released into the system (exergonic)

  • These reactions are usually catabolic (breaking down), as energy is released from broken bonds within a molecule

If the reactants contain less energy than the products, free energy is lost to the system (endergonic)

  • These reactions are usually anabolic (building up), as energy is required to synthesise bonds between molecules

Reaction Pathways of an Exergonic and Endergonic Process

exergonic vs endergonic