Enzymes

• Enzymes


  Proteins that act as biological catalysts to speed up the rate of a chemical reaction without being changed or used up in the reaction
• Enzymes


  • They are made up in living cells
  • They are necessary to all living organisms as they allow chemical reactions to occur at a rate that sustains life
• Enzyme mechanism


  1. Enzymes are specific to one particular substrate(s)

  2. Substrate moves into the enzyme's active site

  3. Enzyme-substrate complex is formed

  4. Products form and are released from active site

  5. Enzyme is unchanged and will go on to further catalyse reactions
• Enzyme-substrate complex

  Forms when the substrate moves into the enzyme's active site
• When an enzyme and its complementary substrate randomly collide, an enzyme-substrate complex forms
• Products form and are released from the active site, the enzyme is unchanged and will go on to further catalyse reactions
• Enzymes

  • They have a specific shape, held in place by bonds, which is extremely important around the active site
  • If the bonds that hold the enzyme together are broken or disrupted, the active site will lose its shape - this is known as denaturation
• Denaturation of an enzyme is irreversible
• Denaturation can occur from high temps or extreme pHs
• Optimum pH


  The optimum pH for most human enzymes is pH 7, some enzymes produced in acidic conditions have lower optimum (pH 2), some produced in alkaline conditions have higher optimum (pH 8/9)
• If the pH is too far above or too far below the optimum


  The bonds that hold the amino acid chain together to make up the protein can be disrupted or broken, changing the shape of the active site so the substrate can no longer fit into it, reducing rate of activity
• Moving too far away from the optimum pH will cause the enzyme to denature
• Optimum temperature


  Enzymes work fastest at their optimum temperature, which for humans is around 37°C
• Heating to high temps (beyond optimum)

  Will break the bonds that hold the enzyme together and the active site will lose its shape, the enzyme is now denatured
• As temperature increases

  The activity of enzymes increases, as the molecules have more kinetic energy, move faster and have more successful collisions, resulting in a faster rate of reaction
• Low temperatures do not denature enzymes, they are just more slow due to lack of kinetic energy
• Enzymes


  • Catalysts produced by living things
  • Have thousands of different sites going on
  • Can greatly speed up reactions
  • Reduce the need for high temperatures in the body
• Catalyst

  A substance which increases the rate of a chemical reaction without being changed itself
• Enzymes are all proteins and all proteins are made up of chains of amino acids
• These chains are folded into shapes which agree with the substrates
• Enzymes


  • Are very specific
  • Usually only speed up substrates
  • Have an active site where the substrate joins
• Lock and key model

  The substrate fits into the enzyme just like a key fits into a lock
• Changing the temperature


  Changes the rate of an enzyme-catalysed reaction
• Higher temperature

  Increases the rate of reaction
• Temperature gets too high


  Some of the bonds holding the enzyme together break, changing the shape of the active site, so the substrate can no longer fit
• Denatured

  When an enzyme's shape is changed so it can no longer function
• All enzymes have an optimum temperature that they work best at
• pH changes


  Interferes with the bonds holding the enzyme together, changing the shape of the active site and denaturing the enzyme