paper 1 required practicals

• What is the first step in preparing a slide of plant cells?

  Use a scalpel to extract a thin layer
• Why is iodine solution added to the slide?

  To stain the nuclei and enhance contrast
• How should the cover slip be lowered onto the slide?

  Gently with a mounted needle to avoid bubbles
• What is the first lens to use when observing the slide?

  The lowest objective lens
• What is the purpose of using coarse and fine focus when observing cells?

  To bring the cells into sharp detail
• What should be done after switching to a higher power lens?

  Use the field of view and magnification formula
• What is the independent variable in the microscopy experiment?

  Magnification
• What is the dependent variable in the microscopy experiment?

  Visibility/detail of cell structures
• What are the control variables in the microscopy experiment?

  Thickness of specimen, light intensity, stain used
• What equipment is needed for the microscopy experiment?

  Microscope, slide, cover slip, iodine
• What are the risk factors associated with the microscopy experiment?

  Scalpel cutting hazard; iodine irritant
• What is the first step in investigating osmosis in potato tissue?

  Use a cork borer to extract cylinders
• Why is it important to measure the initial mass of potato cylinders?

  To compare changes after osmosis occurs
• What should be done with the potato pieces after being placed in sucrose solutions?

  Remove, blot gently, and reweigh
• How can the isotonic point be determined from the experiment?

  By graphing percentage change in mass
• What is the independent variable in the osmosis experiment?

  Sucrose concentration
• What is the dependent variable in the osmosis experiment?

  Percentage change in mass
• What are the control variables in the osmosis experiment?

  Potato type, size, temperature, volume of solution
• What equipment is needed for the osmosis experiment?

  Cork borer, scalpel, balance, boiling tubes
• What are the risk factors associated with the osmosis experiment?

  Sharp tools injury risk; glass breakage
• What is the first step in investigating the effect of pH on amylase activity?

  Label a spotting tile and add iodine
• Why is a water bath used in the amylase activity experiment?

  To maintain optimum temperature at 37°C
• How often should samples be taken to test for starch digestion?

  Every 30 seconds
• What indicates that starch digestion is complete in the amylase experiment?

  When iodine no longer turns blue-black
• What is the independent variable in the amylase activity experiment?

  pH of the buffer
• What is the dependent variable in the amylase activity experiment?

  Time for starch to be broken down
• What are the control variables in the amylase activity experiment?

  Temperature, enzyme concentration, starch concentration
• What equipment is needed for the amylase activity experiment?

  Water bath, iodine, spotting tile, pipettes
• What are the risk factors associated with the amylase activity experiment?

  Corrosive chemicals; hot water burn risk
• What is the first step in testing for starch in a food sample?

  Crush the food sample and mix with water
• What indicates a positive result for starch testing?

  Blue-black color after adding iodine
• How is reducing sugar tested in a food sample?

  Add Benedict’s solution and heat to 80°C
• What indicates a positive result for reducing sugars?

  Red precipitate indicates high sugar content
• What is the testing method for proteins in a food sample?

  Add Biuret A and B; look for purple
• What indicates a positive result for proteins?

  Purple color after adding Biuret solution
• How is lipid presence tested in a food sample?

  Mix with ethanol, then add water
• What indicates a positive result for lipids?

  Milky white emulsion after adding water
• Why should all tests be done with controls?

  To verify the accuracy of results
• What is the first step in investigating light intensity on photosynthesis?

  Place pondweed in a beaker with CO₂
• What is the purpose of counting bubbles of oxygen released?

  To measure the rate of photosynthesis