bio paper 1 required practicals

• What is the aim of the microscopy practical?

  To use a light microscope to investigate a selection of plant and animal cells.
• What equipment is needed for the microscopy practical?

  • Light microscope
  • Microscope slide
  • Cover slip
  • Onion
  • Forceps
  • Iodine solution
  • White tile
  • Scalpel
  • Any other prepared plant and animal cell slides
• Why is iodine solution used in the microscopy practical?

  To stain the cells for better visibility under the microscope.
• What is the first step in the microscopy method?

  Peel off an epidermal layer on the onion using forceps.
• How should the onion tissue be prepared on the microscope slide?

  It should be mounted with a drop of water and lie flat.
• What should be done after adding iodine solution to the slide?

  Place the cover slip on the slide carefully to avoid air bubbles.
• What is the purpose of using paper towels after staining the cells?

  To remove any excess stain from the slide.
• What should you do before looking into the eyepiece of the microscope?

  Use the coarse adjustment knob to raise the stage until the cover slip just touches the objective.
• Why is it important to move the stage away after looking into the eyepiece?

  To avoid breaking the slide while focusing the image.
• What should be done after selecting a high power objective?

  Repeat the focusing process using the fine adjustment knob.
• What should you include in your drawing of the cells observed under the microscope?

  • Labelled drawing of the cells
  • Features such as cell wall and nucleus
  • Magnification used
• What is the final step in the microscopy practical using a prepared slide?

  Repeat the same steps as with the onion slide.
• What safety precaution should be taken when handling iodine solution?

  Wear safety goggles.
• What is the aim of the osmosis practical investigation?

  To investigate the movement of water by osmosis into or out of plant tissue
• What equipment is needed for the osmosis practical investigation?

  • Plant tissue (e.g., potato)
  • Cork borer
  • Ruler
  • Measuring cylinder
  • Labels
  • Boiling tubes
  • Test tube rack
  • Paper towels
  • Sharp knife
  • White tile
  • Range of salt or sugar solutions
  • Distilled water
  • Top-pan balance
• How should the potato cylinders be prepared for the osmosis experiment?

  Cut 5 potato cylinders using a cork borer and trim them to about 3 cm in length
• What should be done after measuring the initial length and mass of each potato cylinder?

  Add one potato cylinder to each boiling tube with known mass and length
• What is the procedure for measuring the sugar solution in the experiment?

  Measure 10 cm$^3$ of the sugar solution and transfer it to a boiling tube
• Why is it important to leave the potato cylinders in the boiling tubes overnight?

  To allow sufficient time for osmosis to occur
• What should be done after removing the potato cylinders from the boiling tubes?

  Blot them dry with paper towels
• How do you calculate the percentage change for each potato cylinder?

  Calculate the change in mass or length and divide by the initial value, then multiply by 100
• What graphs should be plotted after the experiment?

  • Change in mass (in g) against the concentration of sugar solution
  • Change in length (in mm) against the concentration of sugar solution
• What are the sources of error in the osmosis experiment?

  • Discs from different parts of the potato may have different water potentials
  • Different surface areas of potato discs may affect the rate of osmosis
• What safety precautions should be taken during the experiment?

  Take care when handling the cork borer and sharp knife
• What is the aim of the food tests in AQA Biology GCSE?

  To conduct qualitative chemical tests for starch, reducing sugars, proteins, and lipids.
• What are the main tests conducted for food analysis?

  • Iodine test for starch
  • Benedict’s test for reducing sugars
  • Biuret test for proteins
  • Emulsion test for lipids
• What equipment is needed for the iodine test for starch?

  Food sample, test tube, iodine solution, and pipettes.
• What is the method for conducting the iodine test for starch?

  Put food sample in a test tube, add iodine solution, and observe for a color change.
• What indicates the presence of starch in the iodine test?

  The solution turns from brown to blue-black.
• What equipment is needed for the Benedict’s test for reducing sugars?

  Food sample, test tube, Benedict’s solution, hot water bath, thermometer, and pipettes.
• What is the method for conducting the Benedict’s test for reducing sugars?

  Add Benedict’s solution to the food sample, heat in a hot water bath, and observe for color change.
• What indicates the presence of reducing sugars in the Benedict’s test?

  A brick red precipitate is formed.
• What equipment is needed for the protein test?

  A test tube, a 10cm³ measuring cylinder, and Biuret solution.
• What is the method for conducting the protein test?

  Add Biuret’s reagent to the food sample, mix, and wait for a few minutes.
• What indicates the presence of protein in the Biuret test?

  The solution turns from blue to purple.
• What equipment is needed for the lipid test?

  Food sample, test tube, ethanol, and distilled water.
• What is the method for conducting the lipid test?

  Add ethanol to the food sample, mix, and pour into distilled water.
• What indicates the presence of lipids in the emulsion test?

  A white emulsion is formed on the surface of the mixture.
• What are the sources of error in the food tests?

  • Subtle color changes in Benedict’s and Biuret tests may be difficult to judge.
  • Low concentration of tested molecules can affect results.
• What safety precautions should be taken during the food tests?

  • Tie hair back and wear safety goggles during the Benedict’s test.
  • Handle Biuret solution with care due to its toxic components.
  • Keep ethanol away from flames as it is highly flammable.