Required Practicals

• RP7: Why draw the origin line in pencil?

  • Ink from the pen would dissolve in the solvent and run. Therefore mixing with leaf pigments.
• RP7: Why should you draw a line where the solvent meets immediately?

  • The solvent evaporates rapidly so the end position is not available to see shortly after the experiment.
• RP7: Why should you measure the RF value from the middle of the pigment?

  • The pigment mark is spread out, so by measuring from the middle position each time, it is a way to standardise measurements you are taking to allow for comparisons.
• RP7: Why should you make your chromatography paper straight and vertical?

  • So the pigment moves straight up the paper to avoid them running off the side of the paper and/or being washed off.
• RP8: Explain the use of a test tube with chloroplast suspension and water

  • A standard to compare with the experimental test tube to identify decolourisation end point. (Just the chloroplast colour)
• RP8: Explain the use of a test tube with chloroplast suspension, water and DCPIP, covered in foil

  • To prove decolourisation will not occur without light.
  • Electrons are released during LDR
• RP8: Explain the use of a test tube with water, DCPIP and isolation medium

  • To provide that chloroplasts are needed.
  • Dehydrogenase is with chloroplasts
• RP8: Explain the use of test tube with chloroplast suspension, water and DCPIP.

  • Experimental test tube 1
  • To investigate the time taken for DCPIP to turn colourless
• RP8: Explain the use of a test tube with chloroplast suspension, water, DCPIP and ammonium hydroxide

  • Experimental test tube 2
  • To investigate the time taken for DCPIP to decolourise with ammonium hydroxide, effect on dehydrogenase activity
• RP8: Why must all solutions be ice-cold?

  • To slow activity of enzymes which could damage chloroplasts that were released from blending.
• RP8: Why must the isolation medium be an isotonic solution?

  • Isotonic means the solution has the same water potential as chloroplasts.
  • Therefore preventing the chloroplasts bursting or shrivelling.
• RP8: Why were the spinach leaves blended?

  • To release chloroplasts by breaking open cells.
• RP8: Why was the blended spinach filtered?

  • To remove large pieces of cell debris and other organelles.
• RP8: Ammonium hydroxide and other electron accepting chemicals are used as weedkillers, suggest how they may kill weeds?

  • Ammonium hydroxide slows the LDR, therefore ATP and NADPH production reduced.
  • Without ATP and NADPH the LIR will stop and organic substances will not be produced.
• RP 9: Why must both solutions be left in the water bath for 5 minutes before the reaction?

  • So the yeast and TTC both equilibriums to the test temperature
• RP9: Why did the TTC turn red?

  • Dehydrogenase removed H from NADH and TTC picked up H. This will reduce TTC so it produced a red precipitate.
• At which stages of respiration will dehydrogenase be removing hydrogen?

  • NADH is made during glycolysis, link reaction and Krebs cycle.
  • This is because dehydrogenase removes H from carbon compounds.
  • Dehydrogenase also removes H from all the reduced coenzymes in oxidative phosphorylation.
• RP10: Suggest a null hypothesis for this investigation

  • There will be no difference in the number of invertebrates in light/dark, humid/dry chambers.
• RP10: What is the purpose of silica beads?

  • Silica gel absorbs moisture, reducing humidity of the air and creating a dry environment.
• Rp10: Once adding dampened filter paper, to the choice chamber, you should wait 5 minutes before starting experiment why?

  • Provides time for water from the filter paper to start to evaporate to create a humid environment, which reaches nylon mesh.
• RP10: Instead of removing the lid and counting invertebrates. Suggest and explain a different method to increase accuracy?

  • Remove the lid and instantly take a photo.
  • Count the distribution of invertebrates from your photo.
  • This is more accurate as you count the exact distribution before the invertebrates have a chance to move into a different chamber once the lid is removed.
• Rp10: Explain why most invertebrates move to the dark and humid chamber

  • Humid environment is advantageous as it prevents desiccation.
  • Dark environment is advantageous as it is harder for predators to locate and may prevent desiccation.
• RP10: What type of simple behaviour in this experiment are the invertebrates demonstrating?

  • Taxis: organisms is moving its body towards a favourable position.