Enzymes and digestion

• Starch, proteins and fats are large molecules that are too big to pass through the walls of the digestive system
• Digestive enzymes break down large molecules into smaller ones like sugars, amino acids, glycerol and fatty acids
• Small soluble molecules can pass easily through the walls of the digestive system, allowing them to be absorbed into the bloodstream
• Amylase:

  • breaks down starch into maltose
  • made in the salivary glands, the pancreas and the small intestine
• Amylase is a carbohydrase
• Protease:

  • breaks down proteins into amino acids
  • made in the stomach, the pancreas and the small intestine
• In the stomach, protease is called pepsin
• Lipase:

  • breaks down lipids into glycerol and fatty acids
  • made in the pancreas and the small intestine
• Lipids

  fats and oils
• The products of digestion can be used to make new carbohydrates, proteins and lipids
• Some of the glucose produced from digestion can be used for respiration
• Carbohydrase

  an enzyme that breaks down carbohydrates
• Enzymes in the digestive system are produced by specialised cells in glands and in the gut lining
• Salivary glands: produce amylase in the saliva
• Stomach:

  • pummels food with its muscular walls
  • produces the protease enzyme, pepsin
  • produces hydrochloric acid to kill bacteria and give the right pH for pepsin to work
• Liver: produces bile
• Bile

  neutralises stomach acid and emulsifies fats
• Gall bladder: where bile is stored before being released into the small intestine
• Pancreas: produces protease, amylase and lipase enzymes and releases them into the small intestine
• Large intestine: where excess water is absorbed from the food
• Small intestine:

  • produces protease, amylase and lipase enzymes
  • absorbs digested food out of the digestive system and into the blood
• Rectum: where faeces are stored before they are released through the anus