Digestive enzymes

• Large food molecules are digested by enzymes into smaller molecules
• Smaller molecules of food are absorbed into the bloodstream
• enzymes are specific, the substrate must fit perfectly into the active site (lock key theory)
• Proteins are broken down by enzymes called proteases into amino-acids
• Where can protease be found?

  stomach

  Pancreas

  Small intestine
• When amino acids are absorbed by the body cells, they are joined together in a different order to make human proteins
• Carbohydrates are broken down by enzymes called carbohydrates (amylase) to produce simple sugars
• Amylase is found in the saliva and pancreatic fluid
• Lipids are digested by the enzyme lipase to produce glycerols and fatty acids
• Lipase is found in pancreatic fluid and small intestine
• Bile is made in the liver and stored in gallbladder
• Bile helps speed up the digestion of lipids but bile is not an enzyme
• Bile emulsifies the lipid :

  Massively increases the surface area of the lipid droplets

  This increases the rate of lipid breakdown by lipase
• Bile is alkaline, neutralised stomach acids, creating alkaline conditions in the small intestines

  this increases the rate of lipid digestion by lipase
• As the temperature increases, the enzyme and substrate are moving faster so there are more collisions per second between the substrate and active site
• At the optimum temperature there is the maximum frequency of successful collisions between the substrate and active site
• At high temperatures, the enzyme molecule vibrates and the shape of the active site changes , now the substrate no longer fits perfectly into the active site, active site is denatured. enzyme can no longer catalyse the reaction