practicals paper 1

• What is the aim of the microscopy procedure described?

  To investigate plant and animal cells
• What equipment is needed for the microscopy procedure?

  • Light microscope
  • Microscope slide
  • Cover slip
  • Onion
  • Forceps
  • Iodine solution
  • White tile
  • Scalpel
  • Prepared plant and animal cell slides
• Why is it important to peel off the epidermal layer of the onion?

  To obtain a single layer of cells for observation
• How should the onion tissue be mounted on the microscope slide?

  With a drop of water, lying flat
• How many drops of iodine solution should be added to stain the cells?

  Two drops
• What is the purpose of placing the cover slip on the slide?

  To protect the specimen and prevent contamination
• What should be done to avoid trapping air bubbles under the cover slip?

  Lower the cover slip slowly from one edge
• What should be done with excess stain after adding iodine?

  Soak it with paper towels
• What is the first step after preparing the slide?

  Place the slide on the stage of the microscope
• What should be done before looking into the eyepiece of the microscope?

  Use the coarse adjustment knob to raise the stage
• Why is it important to move the stage away after touching the cover slip?

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

  Repeat the focusing process with the fine adjustment knob
• What should be included in the labelled drawing of the cells?

  Features like cell wall and nucleus
• What should be done after making a drawing of the cells?

  Write down the magnification
• What should be done after completing the steps with the onion slide?

  Repeat the steps using a prepared slide
• What safety precaution should be taken when handling iodine solution?

  Wear safety goggles
• What is the aim of the experiment described?

  Investigate the effect of antiseptics on bacteria
• What equipment is needed for the experiment?

  • Agar plate
  • Heatproof mat
  • Filter paper discs
  • Three antiseptics (e.g., mouthwash, TCP, antiseptic cream)
  • Disinfectant bench spray
  • 1% Virkon disinfectant
  • Antibacterial handwash
  • Forceps
  • Clear tape
  • Wax pencil or permanent marker
  • Incubator set to 25°C
• What should you do before handling bacteria in the experiment?

  Wash your hands before and after handling
• What is the purpose of marking the agar plate?

  To identify segments and bacteria used
• At what temperature should the incubator be set?

  25°C
• What are the steps in the method for the experiment?

  1. Spray and wipe the bench with disinfectant.
  2. Mark the agar plate with segments and dots.
  3. Wash hands with antibacterial handwash.
  4. Place antiseptics on filter paper discs.
  5. Use forceps to place discs on agar.
  6. Tape the lid on the agar plate.
  7. Incubate at 25°C for 48 hours.
  8. Measure the diameter of clear zones.
• Why should the lid of the agar plate be taped loosely?

  To allow oxygen to reach the bacteria
• What is the formula to calculate the area of the clear zones?

  Area = πr²
• What sources of error are mentioned in the study material?

  Irregular shape of clear zone and contamination
• What should you do after measuring the clear zones?

  Record the results in a table
• What is the purpose of using different concentrations of antiseptic?

  To investigate the optimum concentration for killing bacteria
• What safety precaution should be taken when handling Virkon disinfectant?

  Wear safety goggles
• How should you place the filter paper discs on the agar plate?

  Using forceps at an angle
• What is the significance of measuring the diameter at 90 degrees?

  To obtain an accurate mean measurement
• What might happen if contamination occurs during the experiment?

  Results may be inaccurate or invalid
• Why is it important to use different antiseptics in the experiment?

  To compare their effectiveness against bacteria
• How long should the agar plate be incubated?

  48 hours
• What is the aim of the investigation?

  To investigate water movement by osmosis
• What is the method used to measure the effect of salt or sugar solutions on plant tissue?

  By measuring changes in length or mass
• What equipment is needed for the investigation?

  • Plant tissue (e.g., potato)
  • Cork borer
  • Ruler
  • Measuring cylinder
  • Labels
  • Boiling tubes
  • Test tube rack
  • Paper towels
  • Sharp knife
  • White tile
  • Salt or sugar solutions
  • Distilled water
  • Top-pan balance
• How long should the potato cylinders be cut to?

  About 3 cm
• How much of the sugar solution is measured for the first boiling tube?

  10 cm​3​
• What should be done with the potato cylinders before placing them in the boiling tubes?

  Measure and record their length and mass
• Why is it important to leave the cylinders in the boiling tubes overnight?

  To allow sufficient time for osmosis