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Monitoring Photosynthesis with DPIP

APBIO-4TY2DJ

Photosynthesis may be studied in a number of ways. For this protocol, a dye-reduction technique is used. This dye-reduction investigation tests the hypothesis that light and chloroplasts are required for the light reactions to occur. A compound, DPIP (2,6-dichlorophenol-indophenol), will be substituted so that when a reduction reaction has occurred, the DPIP changes from blue to colorless.

In this experiment, chloroplasts are extracted from spinach leaves and incubated with DPIP in the presence of light. As the DPIP is reduced and becomes colorless, the resultant increase in light transmittance (at 605 nm, the $A_{max}$ of ‘blue’ DPIP) is measured over a period of time using a spectrophotometer.

Which of the following molecules does DPIP replace in the light reactions of photosynthesis?

A

Chlorophyll.

B

ATP.

C

Ferredoxin.

D

NADP$^+$.