the digestive system

• what are the 3 main nutrients in food?

  • carbohydrates (starch)
  • protein
  • lipids (fats)
• what happens during digestion?

  large food molecules are broken down into small molecules by enzymes, the small molecules can then be absorbed into the bloodstream
• what happens int he first stage of the digestive system?

  food is chewed in the mouth, enzymes in the saliva begin to digest the starch into smaller sugar molecules
• what happens when food passes down the oesophagus?

  goes into the stomach and the enzymes begin the digestion of proteins
• what does hydrochloric acid do in the stomach?

  helps the enzymes to digest proteins
• what does the churning action of the stomach muscles do?

  turns the food into a fluid increasing the surface area for enzymes to digest
• what happens in the small intestine during digestion?

  chemicals are released into the small intestine from the liver and the pancreas
• what happens in the pancreas during digestion?

  the pancreas releases enzymes which continue the digestion of starch and protein, they also start the digestion of lipids
• what does the liver release?

  bile
• what does bile do?

  helps speed up the digestion of lipids, it also neutralises the acid from the stomach
• what do the walls of the small intestine release during digestion?

  enzymes to continue the digestion of protein and lipids
• in the small intestine, the small food molecules produced by digestion are absorbed into the bloodstream either by diffusion or by active transport
• where does the fluid make its way to after the small intestine during digestion?

  the large intestine, where water is absorbed into the bloodstream
• some of the glucose produced is used in respiration