Paper 1 Practicals

• Microscopy

  1. Prepare a thin slice of the specimen and place it on a slide
  2. Add a drop of iodine to stain the specimen and place a cover slip on top
  3. Start with the lowest magnification and adjust the focus
  4. Switch to higher magnifications to observe details
  5. Draw and label what you see, including cell structures
• Osmosis

  1. Cut 5 potato cylinders into the same length and dry them
  2. Measure the length and mass of each cylinder
  3. Measure 10 cm^3 of the 1.0M sugar solution and transfer to the first boiling tube and label
  4. Repeat step 3 for other concentrations and distilled water
  5. Add one potato cylinder to each boiling tube
  6. Leave the cylinders in the boiling tube overnight in a test tube rack
  7. Remove the cylinders and dry them with paper towel
  8. Measure length and mass of each cylinder and record measurements
  9. Calculate percentage changes of each cylinder and plot a graph
• Iodine test for starch

  1. Put some food sample into a test tube
  2. Add a few drops of iodine solution to the food sample using a pipette
  3. If starch is present, the solution turns from brown to blue-black
• Benedict's test for reducing sugars

  1. Add an equal volume or excess of Benedict's solution to the food sample in a test tube
  2. Place in a hot water bath for a few minutes
  3. If reducing sugar is present, a brick red precipitate is formed. If absent, solution remains blue
• Test for protein

  1. Add a few drops of Biuret's reagent to the food sample in a test tube
  2. Shake the solution to mix and wait for a few minutes
  3. If protein is present, the solution turns from blue to purple
• Test for lipids

  1. Add a few cm^3 of ethanol to the food sample
  2. Pour this mixture into a test tube of equal volumes of distilled water
  3. If lipids are present, a white emulsion is formed on the surface of a mixture
• Enzymes

  1. add a drop of iodine solution to each well
  2. add 2cm^3 of each buffer solution using a pipette into each test tube
  3. Put the starch, amylase and buffer solution into a water bath at 25 degrees
  4. Wait for a few minutes
  5. Use a pipette to add 2cm^3 of amylase and starch into a test tube of buffer solution
  6. Use a pipette to drop the mixture into the tiles of the well
  7. Repeat step 6 every 30 seconds, until the iodine solution remains brown and does not turn blue-black
  8. Repeat steps 2-7 for buffer solutions and different pH values
  9. Plot a graph of rate of enzyme reaction against pH
• Culturing Microorganisms

  1. Sterilise the petri dish and inoculating loop using heat
  2. Spread bacteria onto the agar plate using the inoculating loop
  3. Place paper discs soaked in different antibiotics on the plate
  4. Incubate the plate at 25*C for 48 hours
  5. Measure the clear zones around each discs to determine effectiveness
• Photosynthesis

  1. Place pondweed in a beaker of water with sodium bicarbonate
  2. Set up a light source at a measured distance from the pondweed
  3. Count the number of oxygen bubbles released in a set time (e.g. 1 minute)
  4. Repeat at different distances by moving the light source
  5. Record the number of bubbles at each distance to determine the effect of light intensity