Digestive enzymes

• Enzymes catalyse chemical reactions
• Enzymes are large protein molecules that have a groove on their surface called the active site
• The active site is where the substrate attaches to
• Enzymes are specific. The substrate must fit perfectly into the active site (the lock and key theory)
• Proteins are broken down by enzymes called proteases
• Proteases are found in the stomach, pancreas and small intestine
• Proteins are long chains of chemicals called amino acids
• When we digest proteins, the protease enzymes, convert the protein back to the individual amino acids, which are then absorbed into the bloodstream
• Starch consists of a long chain of glucose molecules
• Carbohydrates are broken down by enzymes called carbohydrases. in the case of starch this is called amylase
• When carbohydrates like starch are digested we produce simple sugars
• Amylase is found in the saliva and in the pancreatic fluid
• A lipid consists of a molecule of glycerol attached to three molecules of fatty acids
• Lipid molecules are digested by the enzyme lipase. This produces glycerol and fatty acid
• We find lipase in the pancreatic fluid and also in the small intestine
• Digestion of lipids also includes bile
• Bile is made in liver and stored in the gallbladder. Bile helps to speed up the digestion of lipids, but bile is not an enzyme.
• Bile converts a large lipid droplets into smaller droplets
• Bile emulsifies the lipid which massively increases the surface area of a lipid droplets
• Bile increases the rate of lipid breakdown by lipase
• Bile is also alkaline. This allows it to neutralise stomach acid, creating alkaline conditions in the small intestine.
• Glucagon is a hormone which is released from the pancreas in response to low blood glucose levels. Glucagon encourages the liver to convert glycogen into glucose