Enymes + Digestion

• Enzymes


  • They are biological catalysts which speed up the rate of reactions without being used up or destroyed
  • They are all proteins
  • Each enzyme controls one particular reaction
  • They can be re-used
  • They are affected by temperature
  • They are affected by pH
• Digestion of food


  1. Starch broken into maltose (a sugar) by salivary amylase produced in the mouth and pancreas

  2. Protein broken into amino acids by protease produced in the stomach and pancreas

  3. Fat broken into fatty acids by lipase produced in the pancreas
• Enzyme activity with temperature

  1. Inactive at low temperatures

  2. Rate of reaction increases as temperature increases at first

  3. Optimal temperature at 37°C

  4. Denatured at high temperatures
• Optimal temperature


  37°C, where enzymes work best
• Denatured enzyme


  Enzyme whose active site is broken down, therefore cannot bind with the substrate
• Relationshipbetween temperature, kinetic energy and the rate if reaction

  The higher the temperature, the more kinetic energy, therefore a higher rate of reaction
• Different enzymes have different optimum pHs according to where they are found
• Places enzymes can be found

  • Biological washing powder
  • Baby food
  • Juices
• Enzymes in biological washing powder


  • Helps to remove stains quickly
  • Does not need high temperatures to work
  • Relatively cheap
• Enzymes in baby food


  • Helps babies with digestion of food
• Enzymes in juices


  • Helps with the digestion of juice substances
• Enzymes in juices do not need high temperatures to work
• Heterotrophs


  Organisms that feed on different organisms

  Ex. animals, fungi, bacteria
• Autotrophs


  Organisms that produce their own food

  Ex. plants
• Holozoic nutrition


  Taking in food and digesting it inside the body
• Digestion


  1. Ingestion: the intake of food into the mouth

  2. Digestion: the breakdown of large food molecules into smaller ones

  3. Absorption: when the small molecules get into the bloodstream

  4. Assimilation: when the small molecules reach the cells

  5. Egestion: the removal of undigested food
• Digestive system organs


  • mouth
  • oesophagus
  • stomach
  • gall bladder
  • pancreas
  • liver
  • duodenum
  • Small intestine
  • ileum
  • large intestine
  • colon
  • rectum
  • anus
• The stomach has hydrochloric acid which lowers the pH to around 2-3 so that proteins can be digested by peptidases (protease).
• In the duodenum there are alkaline juices from the liver and pancreas which neutralise the acidity of the chyme coming out of the stomach.
• Enzyme activity is affected by pH, enzymes have an optimum pH range where they work best.
• Pepsin is an enzyme produced in the stomach, it breaks down protein into polypeptides.
• Trypsin is an enzyme produced in the pancreas, it breaks down protein into amino acids.
• Mouth


  We chew with our teeth

  ->The breakdown of large food chunks into smaller ones (physical change)

  ->Ingestion
• Saliva


  Salivary amylase -> breaks down the starch into maltose (pH 7)
• Oesophagus

  • Spinchter muscles contract to push food downwards
  • Peristalsis is the contractions and relaxation of a muscle
• Stomach


  Gastric juice: |

  1. hydrochloric acid

  ->Kills any harmful organisms that come with food

  ->Provides the best pH for the enzyme

  2. pepsin -> breaks down protein into amino acids ( pH 9 )

  The stomach is protected from the acid as it has a layer of mucus
• Liver

  • Bile -> Emulsifcation
  • Breaks molecules into smaller ones
• Gall bladder


  Store bile
• Pancreas


  Pancreatic juice:

  1. Sodium Hydrogen Carbonate
  2. Pancreatic amylase breaks down starch into maltose
  3. Tripsin breaks down proteins into amino acids
  4. Lipase breaks down fats into fatty acids + glycerol
• Duodenum


  This is the last stage of digestion. Three accessory organs are attached to it:

  1. Liver
  2. Gall bladder
  3. Pancreas