Digestion

• Digestion


  Food travels from mouth to stomach, through small intestine and large intestine

  
• Salivary glands

  • Make enzymes that are secreted into the mouth
• Pancreas


  • Makes enzymes that are secreted into the small intestine
• Liver


  • Makes bile and the gall bladder stores bile, which is released into the small intestine
• Digestion


  The breakdown of large, insoluble molecules into small, soluble molecules that can be absorbed into the blood
• Digestion breakdown


  • Starch into sugars (glucose)
  • Proteins into amino acids
  • Fats (lipids) into fatty acids and glycerol

  
• Enzymes

  Required for digestion as they catalyse the chemical reactions that breakdown the bonds in the large, insoluble molecules
• Large, insoluble molecule

  • Enzyme required
  • Small soluble molecule
• Some of the glucose is used in respiration, the remaining glucose is used to make carbohydrates
• The amino acids are used in protein synthesis, any not required are transported to the liver and broken down into urea
• The fatty acids and glycerol are used to synthesise fats (lipids)

  
• Digestion takes place in the organs

  1. Salivary Glands

  2. Mouth

  3. Stomach

  4. Pancreas

  5. Liver

  6. Gall Bladder

  7. Small Intestine

  
• Salivary Glands

  • Make salivary amylase and secrete it into the mouth
• Mouth

  • Some starch is broken down into sugars (glucose) using the enzyme amylase

  
• Stomach


  • Hydrochloric acid kills bacteria and provides the optimum pH for the protease enzyme
  • Protease catalyses the breakdown of some protein into amino acids
• Pancreas


  • Makes pancreatic amylase, protease and lipase and secretes them into the small intestine
• Liver


  • Makes bile
• Gall Bladder


  • Stores bile and releases it into the small intestine
• Small Intestine


  • Bile neutralises the stomach acid to provide the optimum pH for the enzymes
  • Bile emulsifies fat/oil to increase the surface area for lipase
  • Starch is broken down into sugars using pancreatic amylase
  • Proteins are broken down into amino acids using protease
  • Fats (lipids) are broken down into fatty acids and glycerol using lipase

  
• Small Intestine Adaptation


  • Many villi and epithelial cells have many microvilli to increase surface area
  • Epithelial wall is one cell thick and cells are flattened for short diffusion pathway
  • Capillary network inside villi for good blood flow and steep concentration gradient
  • Capillary wall is one cell thick and flattened for short diffusion pathway
  • Epithelial cells contain many mitochondria for energy for active transport