Enzymes and digestion

• The enzymes used in digestion are produced by cells and then released into the gut to mix with food
• Digestive enzymes break down big molecules
• Starch, proteins and fats are big molecules. They're too big to pass through the walls of the digestive system, so digestive enzymes break these big molecules down into smaller ones like sugars, amino acids, glycerol and fatty acids
• Smaller, soluble molecules can pass easily through the walls of the digestive system, allowing them to be absorbed into the bloodstream
• Carbohydrases convert carbohydrates into simple sugars
• Amylase is an example of a carbohydrase. It breaks down starch
• Starch is a carbohydrate
• Amylase is made in 3 places:

  • The salivary glands
  • The pancreas
  • The small intestine
• Proteases convert proteins into amino acids
• Proteases are made in 3 places:

  • The stomach (called pepsin)
  • The pancreas
  • The small intestine
• Lipases convert lipids into glycerol and fatty acids
• Lipids are fats and oils
• Lipases are made in 2 places:

  • The pancrease
  • The small intestine
• The body makes good use of the products of digestion. They can be used to make new carbohydrates, proteins and lipids. Some of the glucose (a carbohydrate) that's made is used in respiration
• Bile neutralises the stomach acid and emulsifies fats
• Bile is produced in the liver. It's stored in the gall bladder before it's released into the small intestine
• The hydrochloric acid in the stomach makes the pH too acidic for enzymes in the small intestine to work properly
• Bile is alkaline - it neutralises the acid and makes conditions alkaline. The enzymes in the small intenstine work best in these alkaline conditions
• Bile emulsifies - breaksdown fat molecules into tiny droplets which are water-soluble fats. This gives a much bigger surface area of fat for the enzyme lipase to work on - which makes its digestion faster
• The breakdown of food is catalysed by enzymes
• Enzymes used in the digestive system are produced by specialised cells in glands and in the gut lining
• Different enzymes catalyse the breakdown of different food molecules
• Salivary glands

  • These produce amylase enzyme in the saliva

  
• Liver

  • Where bile is produced. Bile neutralises stomach acid and emulsifies fats

  
• Gall bladder

  • Where bile is stored, before it's released into the small intestine

  
• Large intestine

  • Where excess water is absorbed from the food

  
• Rectum

  • Where the faeces are stored before they pass through the anus

  
• Stomach

  • It pummels the food with its muscular walls
  • It produces the protease enzyme, pepsin
  • It produces hydrochloric acid for 2 reasions: to kill bacteria and to give the righ pH for the protease enzyme to work

  
• Pancreas

  • Produces protease, amylase abd lipase enzymes. It releases these into the small intestine

  
• Small intestine

  • Produces protease, amylase and lipase enzymes to complete digestion
  • This is also where the digested food is absorbed out of the digestive system into the blood