digestive system + enzymes

• equipment for food test for starch?

  pipettes, cavity tile and iodine
• method for food test for starch?

  1. add food sample to cavity tile
  2. crush food sample if solid
  3. add a few drops of iodine
• expected results for food test for starch?

  if starch is present, iodine turns blue-black

  if starch is absent, iodine stays orange/yellow
• what are the 2 types of carbohydrate you can o chemical food tests for?

  glucose and starch
• which enzyme does saliva contain?

  amylase
• what type of digestion occurs in mouth?

  mechanical
• what does the stomach contain?

  hydrochloric acid and enzymes, which chemically break down the food
• where is bile produced?

  liver
• where is bile stored?

  gall bladder
• where is bile released

  small intestine
• function of bile?

  • Emulsifies lipids, breaking them up physically into tiny droplets. to increase surface area for lipase
  • neutralise stomach acid to produce optimum pH for enzymes
• what is amylase?

  enzyme

  breaks down starch into glucose in small intestine
• where is water absorbed into the bloodstream?

  in the large intestine
• where are nutrients like glucose absorbed into the bloodstream?

  by the villi in the small intestine
• purpose of villi?

  to increase surface area for absorption, in small intestine
• define enzyme

  proteins that act as biological catalysts, often breaking down larger, insoluble molecules into smaller soluble molecules to be absorbed into blood
• explain how enzymes are 'specific'

  they only break down the substrates that have complementary active sites - lock and key principle
• what is amylase an example of?

  a carbohydrase enzyme
• what does protease break down?

  proteins into amino acids
• what do lipases break down?

  lipids into glycerol and fatty acids
• what does amylase break down?

  starch into glucose
• define enzyme activity

  rate of enzyme reactions
• activity of enzyme increases with temperature, until the enzyme....

  denatures
• define denatured

  To change the shape of an enzyme's active site, for example because of high temperatures or extremes of pH. Denatured enzymes no longer work.
• what are proteins made up of?

  chains of amino acids
• why is enzyme activity low at low temperatures?

  At low temperatures, the number of successful collisions between the enzyme and substrate is reduced because their molecular movement decreases. The reaction is slow.
• how do high temperatures denature enzymes?

  by breaking forces between chains of amino acids that make up the proteins.

  therefore the active site of the shape changes shape, so will no longer fit the substrate, and so reaction stops
• how is the optimum pH in the stomach produced?

  by the release of hydrochloric acid
• how is the the optimum pH in the duodenum produced?

  the secretion of sodium hydrogencarbonate
• how do extremes of pH denature enzymes?

  Changing the pH will affect the charges on the amino acid molecules. Amino acids that attracted each other may no longer. Again, the shape of the enzyme, along with its active site, will change.
• is denaturing a permanent or temporary change?


  permanent
• which physical factors affect enzyme action?

  temperature and pH
• starch is a type of....

  carbohydrate
• optimum temp/ph =

  the condition for max enzyme rate / activity
• how do you know when all starch has been broken down in enzyme practical?

  when solution remains orange. iodine turns black in presence of starch
• what colour does iodine turn in presence of starch?

  blue / black
• how to find the optimum temp/pH in enzyme practical?

  optimum is between the two lowest times on the graph, as is where starch took the shortest time to be broken down
• food test for sugars?

  benedicts solution

  turns blue to red in presence of glucose
• food test for protein?

  bieurets from blue to purple
• food test for lipids (fats)

  • turns cold ethanol cloudy
  • in sudan 111, brick red layer forms ontop