Enzymes and activation energy

• what is the activation energy?

  the minimum energy that must be put into a chemical system for a reaction to occur
• what must molecules have enough of to approach each other closely enough to react?

  kinetic energy
• whats one way of making chemicals react?

  is to increase their kinetic energy, to make successful collisions between them more likely
• what can heat do in non-living systems?

  it can speed up reactions
• what can heat do in living organisms?

  in more living organisms, temperatures above about 40$^.$c cause irreversible damage to proteins, and they denature
• what can lowering the activated energy do?

  it makes enzymes allow reactions to take place at the lower temperatures found in cells
• how do enzymes act at 0$^.$c ?


  most enzymes are inactive
• how can enzymes lower activation energy?

  • they work by modifying the substrate so the reaction requires a lower activation energy
  • when a substrate enters the active site, the shape of the molecule alters, allowing reactions to occur at lower temperatures (i.e. with lower kinetic energy, than in the absence of enzymes)
• which graph shows the reaction without an enzyme and which one shows with an enzyme?

  left = without enzyme

  right = with enzyme