HIGHER BIOLOGY PAPER 1

• the small intestine, pancreas and salivary glands all produce amylase
• the small intestine, pancreas and stomach all produce protease enzymes
• Eukaryotic cells


  Animal and plant cells
• Prokaryotic cells


  Bacterial cells
• Organelles


  Structures in a cell that have different functions
• Organelles only in plant cells


  • Chloroplasts
  • Permanent vacuole
  • Cell wall
• Structures in bacterial cells

  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Chromosomal DNA (circular)
  • Plasmids
  • Flagella
• Differentiation

  A process that involves the cell gaining new sub-cellular structures in order for it to be suited to its role
• Specialised animal cells

  • Sperm cells
  • Egg cells
  • Ciliated epithelial cells
• Specialised plant cells

  • Root hair cells
  • Xylem cells
  • Phloem cells
• Electron microscopes have allowed the discovery of viruses and detailed examination of proteins
• Magnification

  Magnification of the eyepiece lens x magnification of the objective lens
• Size of an object

  Size of image/magnification = size of object
• Parts of a light microscope

  • Eyepiece
  • Barrel
  • Turret
  • Lens
  • Stage
• Using a light microscope

  1. Place slide on stage

  2. Look through eyepiece

  3. Turn focus wheel

  4. Start with lowest magnification, then increase
• Preparing a slide


  1. Take thin layer of cells

  2. Add chemical stain

  3. Apply cells to slide

  4. Lower coverslip
• Enzymes


  Biological catalysts that increase the rate of reaction without being used up
• Active site


  The uniquely shaped site on an enzyme where the substrate binds
• Lock and key hypothesis

  The shape of the substrate is complementary to the shape of the active site, forming an enzyme-substrate complex
• Actual size


  Measured size / magnification
• Total magnification

  Objective lens magnification x eyepiece lens magnification
• Enzymes


  Biological catalysts (a substance that increases the rate of reaction without being used up)
• Enzymes


  • They are present in many reactions - allowing them to be controlled
  • They can both break up large molecules and join small ones
  • They are protein molecules and the shape of the enzyme is vital to its function
  • Each enzyme has its own uniquely shaped active site where the substrate binds
• Enzymes can only catalyse (speed up) reactions when they bind to a substrate that has a complementary shape, as this is the only way that the substrate will fit into the active site. This is called enzyme specificity.
• Enzymes

  • They require an optimum pH and temperature, because they are proteins
  • They also need an optimum substrate concentration
• Optimum temperature (in humans)

  A range around 37 degrees Celsius (body temperature)
• As temperature increases

  The rate of reaction increases up to the optimum, but above this temperature it rapidly decreases and eventually the reaction stops
• Denaturation

  When the bonds that hold the enzyme together break, changing the shape of the active site so the substrate can no longer 'fit into' the enzyme
• Optimum pH


  7 (neutral) for most enzymes, but some that are produced in acidic conditions, such as the stomach, have a lower optimum pH
• If the pH is too high or too low


  The forces that hold the amino acid chains that make up the protein will be affected, changing the shape of the active site so the substrate can no longer fit in
• Substrate concentration


  The concentration of the substance binding to the enzyme
• As substrate concentration increases


  The rate of reaction will increase - up to a point (the saturation point, which is different for every enzyme)
• In this practical, we are looking at how pH affects the rate of activity of the enzyme amylase
• Amylase breaks down carbohydrates such as starch into simple sugars such as maltose
• We can use iodine (dark orange colour) to check for the presence of starch in the solution at any time. When starch is present, the iodine solution will turn to a blue-black colour.
• Core Practical - Effect of pH on Enzyme Activity


  1. Place single drops of iodine solution on each well of a tray

  2. Label a test tube with the pH to be tested. Place it in a water beaker with 50ml cold water and place this above a Bunsen Burner for 3 minutes

  3. Place 2cm3 of amylase solution, 2cm3 of starch solution and 1cm3 of the buffer pH solution in a test tube and start a stopwatch

  4. After 10 seconds, use a pipette to place a drop the solution into one of the wells containing iodine solution. Repeat every 10 seconds until the solution remains orange, and record the time taken

  5. Repeat with a buffer solution of different pH

  6. Record your results on a graph of pH (on the x-axis) and time taken to complete reaction (on the y-axis)
• We use a Bunsen Burner and water beaker to keep the solution at a relatively constant temperature throughout the reaction (temperature is a control variable in this experiment)
• The optimal pH of amylase will be at whichever pH the reaction completes in the shortest time. This should be somewhere around pH 7.0.
• Rate calculation


  Rate = Change / Time
• Proteases are a type of enzyme used to break down proteins