1.3

• Food molecules


  large molecules - need to break down smaller to get through gut wall

  insoluble particles - must convert to soluble ones to be transported in blood
• Food tests

  • starch - iodine solution, brown -> blue / black
  • glucose - benedict's reagent, blue -> any colour
  • protein - biuret solution, blue -> purple , (irritant)
• Absorption


  transfer of breakdown products into blood

  • small intestine - food
  • large intestine - water
• Digestion


  breakdown of food, mainly in

  • mouth
  • stomach
  • small intestine
• Egestion


  removal of any undigested food via rectum and anus
• The pancreas secretes enzymes that break down carbohydrate, protein and fats.
• The large intestine absorbs water to form faeces.
• Digestive system

  A - mouth

  B - oesophagus

  C - liver

  D - gallbladder

  E - pancreas

  F - stomach

  G - large intestine

  H - small intestine

  I - rectum

  J - anus

  
• Mouth

  • begins digestion of starch
  • secretes amylase
• Oesophagus

  • no digestion
  • food is moved down to stomach through peristalsis
• Liver

  • produces bile
  • bile helps with digestion of fats
• Gallbladder

  • stores bile
  • releases bile into the small intestine
• Pancreas

  • produces carbohydrase and lipase
  • these enzymes both act in the small intestine
• Stomach

  • begins digestion of protein
  • ph of 1-3
  • produces protease
• Large intestine

  • reabsorbs water that has been added to digestive juices
  • produces faeces
• Small intestine

  • pancreatic carbohydrase causes breakdown of starch -> maltose
  • protease completes breakdown of protein -> amino acid
  • pancreatic lipase causes breakdown of fats -> fatty acid and glycerol
  • carbohydrase completes breakdown of carbohydrates -> glucose
• Rectum

  • part of large intestine
  • faeces are stored hwre before egestion
• Anus

  • faeces are egested from here
• Peristalsis


  wave of muscular contractions forcing food down the digestive system
• Carbohydrase

  • breaks down carbohydrates from starch into glucose or simple sugars if starch is not present
  • in mouth, pancreas and small intestine
• Protease

  • digests proteins into amino acids
  • in stomach and small intestine
• Lipases

  • breakdown of fat into glycerol and fatty acids
  • in pancreas and small intestine
• Bile

  • emulsifies fats
  • aids digestion
  • produced in liver
  • stored in gallbladder
• Enzymes

  • carbohydrase
  • protease
  • lipase
  • amylase