Section 1: Enzymes

  • Created by: Bethany
  • Created on: 19-04-19 10:50


  • Enzymes are biological catalysts for chemical reactions, produced by living things
  • Catalysts are substances which speed up reactions but are not changed or used up in the reaction
  • They are made from proteins which are made from chains of amino acids, folded into different shapes for different jobs
1 of 4

Lock and Key Model

  • A substrate is a molecule that is changed in  a reaction
  • Every enzyme molecule has an active site: where the substrate joins to the enzyme
  • Enzymes normally only speed up one type of reaction because the substrate has to be the correct shape to fit the active site
  • This is called the "lock and key" model because the substrate has to fit the active site like a key in a lock
2 of 4

Temperature and Enzyme Activity

  • Temperature affects enzyme activity: at first a higher temp increases the rate, because the enzymes/substrates have more energy and are more likely to collide into enzyme-substrate complexes
  • If it gets too hot, bonds holding the enzyme together start to break which changes the shape of the enzyme so the substrate won't fit properly and the enzyme becomes denatured
  • Every enzyme has an optimum temperature at which they work best, usually around 45°
3 of 4

pH and Enzyme Activity

  • If the pH level of the environment is too high or too low, it interferes with the bonds holding he enzyme together
  • This changes the shape of the active site and again denatures the enzyme
  • All enzymes have an optimum pH that they work best in, usually about pH 7 (neutral) but not always
4 of 4


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Enzymes and digestion resources »