AP Biology Lab 4: Photosynthesis?

Question

What is the source of the electrons that will replace DPIP?What is the effect of darkness on the reduction of DPIP?
What resons can you give for the difference in the percentage of transmittance between the live chloroplasts that were incubated in the light and those that were kept in the dark?

Answer 1

The electrons that reduce DPIP come from chlorophyll in the photosystems; and those electrons came from water molecules. So I guess it depends on how far back you want to go. I would choose to answer "the electrons came from splitting water molecules and were passed to the chlorophyll molecules, eventually being transferred to the DPIP".

Live chloroplasts incubated in the light would carry on photosynthesis and reduce the DPIP, resulting in a color change from blue to clear --> more transmittance. In the dark: no photosynthesis, no reduction of DPIP, no changing of the DPIP from blue to clear, less transmittance.