Enzymes

• Enzymes catalyse specific reactions in living organisms due to the shape of their active site
• Catalysts are substances which increase the rate of reaction without being changed or used up in the reaction
• Every enzyme has an unique active site that fits the substrate like a lock and key
• Changing the temperature changes to rate of an enzyme-catalysed reaction
• If the temperature of an enzyme gets too hot the bonds holding the enzyme together will break changing the active site, so the substrate will not fit and the enzyme is denatured
• The optimum temperature of an enzyme is where the enzyme is more active
• A higher temperature increases the rate at first because the particles have more kinetic energy but once the temperature is too high the enzyme becomes denatured

  
• If the pH is too high or low it interferes with the bonds holding the enzyme together

  
• pH effect on enzymes practical

  • Put a drop of iodine solution in every well of a spotting tile
  • Use a syringe to add 1 cm3 of amylase solution to 1 cm3 of buffer solution with a pH of 5 to a boiling tube
  • Place the test tube in a water bath
  • Use a different syringe to add 5 cm3 of a starch solution to a boiling tube and place in the water bath
  • Mix the both solutions in a boiling tube and start the stopwatch
  • Take a pipette and collect a fresh sample every 30 seconds and but a drop in the well (continuous sampling)
  • When the iodine remains orange starch is no longer present
• Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream
• Carbohydrase's break down carbohydrates to simple sugars. Amylase is a carbohydrase which breaks down starch
• Proteases break down proteins to amino acids
• Lipases break down lipids (fats) to glycerol and fatty acids
• Amylase is made in the salivary glands, pancreas and small intestine
• Protease is made in the stomach, pancreas and small intestine
• Lipase is made in the pancreas and small intestine
• The products of digestion are used to build new carbohydrates, lipids and proteins and some glucose is used in respiration
• How enzymes work

  • Substrate binds to active site because they are complementary
  • Bond between molecules are broken down to produce smaller molecules