Digestive system

• The 7 food groups

  • fats
  • proteins
  • minerals
  • vitamins
  • carbohydrates
  • water
  • fibre
• The 7 food groups represent large chemicals
• These chemicals are often chains of smaller, more useful chemicals, joined together
• Carbohydrates

  Made of long chains of identical small sugar molecules
• Energy molecules in food are carbohydrate sugar molecules
• The small sugar molecules are very useful
• The body has to break these large food molecules up into single or small chain sugar molecules. These are used to make energy
• Physical means like slicing and cleaving food does not break down the long chain molecules and release the sugars
• Chemical bonds require a chemical technique if they are to be broken
• The food we start with is often large in size and being large, the food tends to be unable to dissolve
• Food solubility


  The food needs to be soluble so that it can dissolve in the blood and thus, be transported around the body. The smaller the food, the more likely they will dissolve
• The Digestive System


  1. INGESTION- eating (mouth)

  2. DIGESTION- breaking down molecules (stomach, small and large intestine)

  3. ABSORPTION- taking in digested molecules into cells (whole digestive tract)

  4. EGESTION- removal of wastes (large intestine, anus)
• The digestive system, being an organ system, is made of a group of organs all working together
• Each organ has a particular function and only by working together will they get the job done
• The sound of a rumbling stomach and the fact that food looks very different when it leaves, compared to when it enters mean that the body must be doing something to the food during its journey
• The only visible parts of the digestive system are the entry and exit points
• Digestion


  Breaking down of food
• All food has a physical shape and is made of chemicals. These chemicals are held together by chemical bonds
• Methods of digestion


  • Chemical digestion
  • Physical digestion
• All food enters our digestive system through the mouth and waste material leaves through the anus
• The digestive system is really one long tube with an opening at each end. Stretched out it is a 9m tube!
• The tube passes through organs on its route from the mouth to the anus
• The digestive system is extremely folded to fit into a space less than a metre long
• Physical digestion


  The mechanical act of chewing food
• The mouth produces saliva, a sticky liquid
• Saliva


  Softens the food and allows the digested food to be rolled into a ball just before it is swallowed. It also contains an enzyme
• Enzyme


  Chemicals which act to speed up chemical reactions. They are produced from glandular tissue, which is found all over the body
• Enzymes


  • They have a particular shape, with an active site on the surface
  • They attach to the chemicals that are reacting using their active site
  • They are very specific and can only speed up certain reactions
  • They work best in particular environmental conditions
• Different enzymes work best in different conditions. If the condition is wrong, their active site can change shape and they stop working
• The three main food groups

  • proteins
  • carbohydrates
  • fats
• Carbohydrates


  Chains of identical sugar molecules. The enzyme that digests carbohydrates must be able to break the chemical bonds between the individual sugar molecules
• Amylase


  An enzyme that digests carbohydrates
• Digestion of carbohydrates


  1. Carbohydrates

  2. Sugars
• Proteins


  Made of chains of amino acids, with over 20 different kinds of amino acid
• Proteases


  Enzymes that digest proteins by breaking the chemical bonds between the different amino acids
• Fats/Lipids


  Made up of a molecule of glycerol phosphate attached to three fatty acid molecules
• Lipases


  Enzymes that digest fats by breaking the chemical bonds between the glycerol phosphates and the fatty acids
• Of the three enzymes, the only one released within the mouth is Amylase
• Amylase works best within an alkaline (pH > 7) environment
• Epiglottis


  A flap that prevents food from entering the trachea (windpipe)