organisation

• Cell organisation


  How cells in large multicellular organisms are organised into organ systems
• Differentiation


  The process by which cells become specialised for a particular job
• Large multicellular organisms


  • Have different structures for changing and transporting materials
• Tissue


  A group of similar cells that work together to carry out a particular function
• Organ


  A group of different tissues that work together to perform a certain function
• Organ system


  A group of organs working together to perform a particular function
• Organs in the digestive system

  • Glands (e.g. pancreas, salivary glands)
  • Stomach and small intestine
  • Liver
  • Small intestine
  • Large intestine
• Enzymes are catalysts produced by living things
• Catalyst


  A substance which increases the speed of a reaction, without being changed or used up in the reaction
• Enzymes


  • They have special shapes so they can catalyse reactions
  • They usually only catalyse one specific reaction
• Substrate doesn't match the enzyme's active site

  The reaction cannot be catalysed
• Induced model of enzyme action

  The active site changes shape a little as the substrate binds to it to get a tighter fit
• Increasing temperature


  Increases the rate of an enzyme-catalysed reaction at first
• Temperature getting too high


  Breaks some of the bonds holding the enzyme together, changing the shape of the active site and denaturing the enzyme
• Optimum temperature


  The temperature at which an enzyme works best
• Optimum pH


  The pH at which an enzyme works best
• Pepsin is an enzyme used to break down proteins in the stomach, it works best at pH 2
• Investigating the effect of pH on enzyme activity

  1. Put buffer solution into boiling tube

  2. Add enzyme solution

  3. Add starch solution

  4. Take samples and test for starch

  5. Repeat with different pH buffers
• Rate of reaction


  A measure of how much something changes over time
• Rate of reaction = amount of product formed / time taken
• Enzymes used in digestion are produced by cells and released into the gut
• Carbohydrases


  Enzymes that convert carbohydrates into simple sugars
• Amylase


  An example of a carbohydrase that breaks down starch
• Places amylase is made

  • Salivary glands
  • Pancreas
  • Small intestine
• Proteases


  Enzymes that convert proteins into amino acids
• Places proteases are made

  • Stomach (pepsin)
  • Pancreas
  • Small intestine
• Lipases


  Enzymes that convert lipids into glycerol and fatty acids
• Places lipases are made

  • Pancreas
  • Small intestine
• Bile


  • Produced in the liver, stored in the gall bladder, released into the small intestine
  • Neutralises stomach acid and emulsifies fats
• Bile is alkaline, it makes the conditions in the small intestine alkaline so enzymes can work best
• Parts of the digestive system that produce protease enzymes

  • Stomach (pepsin)
  • Pancreas
  • Small intestine
• Food tests


  1. Prepare food sample

  2. Dissolve in water

  3. Filter to remove solids

  4. Use Benedict's test to test for sugars
• Food Tests


  Ways to identify what type of food molecule a sample contains
• Food testing procedure


  1. Grind up food sample

  2. Add distilled water to ground up food

  3. Stir mixture with glass rod to dissolve some of the food

  4. Filter solution to remove solid bits
• Benedict's Test


  Test for reducing sugars in foods
• Types of sugars


  • Reducing sugars
  • Non-reducing sugars
• Benedict's Test procedure


  1. Prepare food sample

  2. Heat sample in water bath at 25°C

  3. Add Benedict's solution

  4. Leave in water bath

  5. Colour change indicates presence of reducing sugars
• Iodine Solution Test


  Test for presence of starch in foods
• Iodine Solution Test procedure

  1. Prepare food sample

  2. Add iodine solution

  3. Colour change indicates presence of starch
• Biuret Test


  Test for presence of proteins in foods