Human biology - applied science aqa

Cards (20)

  • the components of the digestive system carry out mechanical and chemical digestion.

    Mechanical digestion is the physical breaking up of food into smaller pieces.

    Chemical digestion is the chemical breakdown of large insoluble food molecules into smaller soluble food molecules using digestive enzymes.
  • Each structure in the body has its function:
    • stomach - a large muscular bag that churns food and releases hydrochloric acid and pepsin (protein) for digestion. This is mechanical and chemical digestion.
    • mouth - where food is chewed and mixed with saliva. This is mechanical and chemical digestion.
    • salivary glands - secrete saliva containing the salivary amylase which is a carbohydrase. This is chemical digestion.
    • oesophagus - through which food is moved from the mouth to the stomach. This is no digestion.
    • liver - makes bile. Not a digestion.
  • Gall bladder
    Stores bile. No digestion.
  • Small intestine - ileum
    Absorbs the small soluble of food digestion into the bloodstream. This is chemical digestion.
  • Small intestine - duodenum
    Bile and enzymes are released here for digestion. This is chemical digestion.
  • Large intestine

    Absorbs water from food. No digestion.
  • Pancreas
    Releases proteases, carbohydrases, and lipases into the duodenem. This is chemical digestion.
  • Rectum
    Where feces are compacted and temporarily stored. No digestion.
  • Anus
    Where feces leave the digestive tract. No digestion.
  • Peristalsis:
    food is moved through the digestive system through peristalsis; a wave of muscular contraction.
    -> movement of the food
  • Chemical digestion:
    a chemical reaction involving the breaking of bonds through the addition of a water molecule, using an enzyme.
  • Enzymes:
    enzymes catalyze the hydrolysis of large insoluble food molecules into small soluble food molecules.
    there are 3 types of enzymes; lipases, proteases, and carbohydrases.
  • types of enzymes:
    carbohydrases - carbohydrates like starch/food molecules that are produced are sugars e.g. glucose/ the bond that is broken is glycosidic/ enzymes are made in the salivary glands and pancreas/ yet the enzymes digest food in the small intestine and mouth
  • types of enzymes:
    proteases - proteins/ food molecules produced are amino acids/ peptide bonds are broken/ enzymes are made in the stomach and pancreas/ enzymes digest food in the stomach and small intestine
  • types of enzymes:
    lipases - fats e.g lipids/ food molecules produced are fatty acids and glycerol/ ester bonds are broken/ enzymes are made in the pancreas/ enzymes are digested in the small intestine
  • roles in digestion and how it affects enzyme enzyme-controlledcontrolled digestion:
    hydrochloric acid:
    • gives the stomach a pH of 2
    • because of this, it activates the stomach enzymes providing the optimum pH for their action.
    • killing most bacteria on the food
    • inactivating the salivary amylase
  • roles in digestion and how it affects enzyme-controlled digestion:
    bile:
    • alkaline pH and neutralizes the stomach acid to provide pH 7 <- optimum pH for small intestine enzymes
    • emulsifies fats providing a larger surface area for lipase action.
  • roles in digestion and how it affects enzyme-controlled digestion:
    mucus:
    • protects stomach lining from being digested by protease enzymes
    • protects stomach from hydrochloric acid burns
    • lubricates food so it passes down the digestive tract more easily
  • what is gastrin?
    • a hormone that is released when a protein is detected in the stomach
    • stimulates the release of hydrochloric acid and protease enzymes from the cells lining the stomach
    • promotes contraction from the stomach muscles
    • relaxes the sphincter muscle bottom of the stomach
    • this increases the rate of the stomach emptying
    • increases flow of bile from the gall bladder
  • Model answer for chemical digestion of proteins:
    • Proteins are digested by protease enzymes.
    • They digest proteins into amino acids by catalysing hydrolysis reactions which break the peptide bonds in the protein.
    • Protease enzymes are made by the stomach and small intestine.
    • Protein digestion starts in the stomach where the optimum pH of 2 is created by the release of hydrocholric acid.
    • The digestion is completed in the small intestine, where the optimum pH is created by bile neutralising the hydrochloric acid.