Digestive enzymes

• Enzymes catalyze chemical reactions by speeding them up
• Enzymes are large protein molecules with a groove on their surface called the active site
• The active site is where the substrate attaches, and the substrate is the molecule that the enzyme breaks down
• Enzymes are specific, and the substrate must fit perfectly into the active site (lock and key theory)
• Specific enzymes in the digestive system:

  • Proteins are broken down by proteases found in the stomach, pancreatic fluid, and small intestine
  • Proteases convert proteins into individual amino acids for absorption into the bloodstream
  • Carbohydrates like starch are broken down by amylase enzymes found in saliva and pancreatic fluid
  • Amylase converts starch into simple sugars
  • Lipids are broken down by lipase enzymes found in the pancreatic fluid and small intestine
  • Lipase converts lipids into glycerol and fatty acids
• Bile in the digestion of lipids:

  • Bile is made in the liver and stored in the gallbladder
  • Bile helps to speed up the digestion of lipids by emulsifying large lipid droplets into smaller droplets
  • Emulsification increases the surface area of lipid droplets, enhancing the rate of lipid breakdown by lipase
  • Bile is alkaline, neutralizing stomach acids and creating alkaline conditions in the small intestine
  • Alkaline conditions in the small intestine further increase the rate of lipid digestion by lipase