Demonstrating the role of hydrogen acceptors

• 1. Place 5g of chopped lettuce in a mortar with 10cm3 of buffer solution and grind with pestal
• 2. Pour contents of the mortar through muslim to filter into beaker
• 3. Pour the suspension into centrifuge tubes, counterbalancing the tubes
• 4. Centrifuge at high speed for 10-12 minutes
• 5. Pour off and sucked the supernatant of the centrifuge tubes to remove organelles smaller than chloroplasts
• 6. The sedimented chloroplasts in the centrifuge tubes can be added to two tubes (A+B). Buffer is also added. One of these tubes with chloroplasts is covered with foil (B) to prevent light reaching the chloroplast. Tube C contains buffer
• 7. DCPIP is added to each of the tubes and the tubes are placed in a beaker of crushed ice
• 8. The beaker containing the tubes is placed under a very strong light source and the colour of each tube is examined every 5 minutes for 20 minutes (4 times)
• 9. Tube A changes from blue-green to green as the chloroplasts are green, this shows that the DCPIP is reduced due to the electrons produced during the light dependent stage

  Tube B stays blue-green as the DCPIP is not reduced as the chloroplasts are not illuminated, light dependent stage does not occur