Factors that Affect the Light Reaction of Photosynthesis: Teacher Information
(Download the MS Word version of this document.)
Safety
CAUTION: Be sure to warn your students about the fact that DPIP may stain their skin or clothing.
Solutions
To make the chloroplast solution, use 50 g of fresh spinach with 250 ml of a 0.5M cold sucrose solution. Make the sucrose solution by using 171 g of sucrose and bring to a l liter with distilled H2O. Take the sucrose sugar solution and the spinach and put into a blender. You may have to tear the leaves. Blend the spinach with three 5-10 second bursts. Pour through several layers of cheese cloth. Keep on ice. This will last only 1-2 hours, after which new chloroplasts suspensions should be made.
0.1- M Phosphate Buffer is made by taking 174 g K2HPO4 (dibasic) brought to liter of distilled H2O and 136 g KH2PO4 (monobasic) brought to 1 liter with distilled H2O. Mix 685 ml of KH2PO4 (monobasic) with 315 K2HPO4 (dibasic). The pH should be 6.5, if not adjust accordingly. Since this is a 1 M solution it must be diluted to 0.1 M by taking 100 ml of the 1 M phosphate buffer solution and adding 900 ml of distilled water.
DPIP(2-6 Diphosphoindol phenol) solution is made by bringing 0.072 g to 1 liter of water. This solution in its oxidized state is a blue dye.
CAUTION: This may stain clothing and skin. Use care when handling this solution. Light will reduce this solution so it needs to be stored in the dark either in amber bottles or the refrigerator. The effect of light on the DPIP during the lab is negligible. Also, if you are just playing around with this lab and leave the DPIP out in an open beaker, the amount of water that evaporates will effect concentration of DPIP. This will make the DPIP much darker and will effect the results.
