organisation

• Cell organisation


  How cells in large multicellular organisms are organised to form a working organism
• Large multicellular organisms are made up of organ systems
• Cells


  • They are the basic building blocks that make up all living organisms
  • Specialised cells carry out a particular function
• Differentiation


  The process by which cells become specialised for a particular job
• Differentiation occurs during the development of a multicellular organism
• Specialised cells form tissues, which form organs, which form organ systems
• 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
• Tissues in the stomach

  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Organ system


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

  • Glands (e.g. pancreas and salivary glands)
  • Stomach and small intestine
  • Liver
  • Small intestine
  • Large intestine
• Organ systems work together to make entire organisms
• Enzymes


  Catalysts produced by living things that speed up chemical reactions without being consumed or permanently altered
• Enzymes


  • They have thousands of different chemical reactions going on inside them all the time
  • They reduce the activation energy needed for reactions to occur
• Active site


  The unique shape of an enzyme that allows it to bind to and catalyse a specific reaction
• Lock and key model


  A simplified model of how enzymes work, where the substrate fits into the active site like a key in a lock
• Induced fit model


  A more accurate model of how enzymes work, where the active site changes shape to better fit the substrate
• Increasing temperature


  Increases the rate of an enzyme-catalysed reaction at first, but too high a temperature denatures the enzyme
• Changing pH


  Can denature enzymes by interfering with the bonds holding the enzyme together
• Optimum temperature and pH


  The temperature and pH at which an enzyme works best
• Investigating the effect of pH on enzyme activity

  1. Put iodine solution in wells

  2. Heat water bath to 35°C

  3. Add amylase and buffer solution to tube, incubate for 5 mins

  4. Add starch solution

  5. Take samples every 30 seconds and test for starch

  6. Repeat with different pH buffers

  7. Calculate rate of reaction
• Rate of reaction


  A measure of how much a reaction changes over time, calculated as amount of product formed / time taken
• Carbohydrases


  Enzymes that break down carbohydrates into simple sugars
• Proteases


  Enzymes that break down proteins into amino acids
• Lipases


  Enzymes that break down lipids into glycerol and fatty acids
• Bile


  Produced in the liver, it neutralises stomach acid and emulsifies fats to aid digestion
• Enzymes used in digestion are produced by specialised cells in glands and the gut lining
• Locations of digestive enzymes

  • Saliva (amylase)
  • Stomach (pepsin)
  • Pancreas
  • Small intestine
• The stomach produces hydrochloric acid to kill bacteria and provide the right pH for pepsin to work
• Food tests


  1. Grind up food sample

  2. Add water

  3. Filter

  4. Use Benedict's test to test for sugars
• Rectum


  Where the faeces (made up mainly of indigestible food) are stored before they bid you a fond farewell through the anus
• Food Tests


  1. Cut a piece of food and break it up using a pestle and mortar

  2. Transfer the ground up food to a beaker and add some distilled water

  3. Give the mixture a good stir with a glass rod to dissolve some of the food

  4. Filter the solution to remove bits of food
• Benedict's Test


  Used to test for sugars in foods
• Sugars


  There are two types - reducing and non-reducing
• Benedict's Test


  1. Prepare food sample

  2. Prepare a water bath set to 80°C

  3. Add Benedict's reagent to the hot test tube

  4. Place the test tube in the water bath for 5 minutes

  5. If the food sample contains reducing sugars, the solution will change colour from blue to green, yellow or brick-red
• Iodine Solution Test


  Used to test for the presence of starch in foods
• Iodine Solution Test


  1. Make a food sample and transfer 5cm³ to a test tube

  2. Add a few drops of iodine solution and gently shake the tube

  3. If the sample contains starch, the colour will change from brown-orange to black or blue-black
• Biuret Test


  Used to test for the presence of proteins in foods
• Biuret Test


  1. Prepare a sample of the food and transfer 2cm³ to a test tube

  2. Add 2cm³ of biuret solution and mix the contents

  3. If the food sample contains protein, the solution will change from blue to purple
• Sudan III Test


  Used to test for the presence of lipids (fats) in foods