Instructions for the Photosynthesis Lab Report

Lab 4 of the required labs in AP Biology involves an experimental examination of two aspects of photosynthesis, namely the pigments and the light reaction. In your lab report answer the following questions for each section.

Plant Pigments

1. The relationship of the distance moved by a pigment to the distance moved by the solvent is a constant called Rf . It can be calculated for each of the pigments using the formula:

Rf = distance pigment migrated (mm) / distance solvent front migrated (mm)

Prepare a table of Rf values from the chromatograms provided in the handout section of the web page. There are four primary pigments: beta-carotene, xanthophyll and chlorophyll a & b.

2. What factors are involved in the separation of the pigments?

3. Would you expect the Rf value of a pigment to be the same if a different solvent were used? Explain

4. What type of chlorophyll does the reaction center contain? What are the roles of the other pigments?

Light Reaction of Photosynthesis

1. What is the purpose of DPIP in the experiment?

2. What molecule, found in chloroplasts, does DPIP “replace” in this

experiment?

3.What is the source of electrons that will reduce DPIP?

4. What was measured with the spectrophotometer in this experiment?

5. What is the effect of darkness on the reduction of DPIP? Why did this happen?

6. What is the effect of boiling the chloroplasts on the reduction of DPIP? Why did this happen?

7. Why was there a difference in the absorbance between the live chloroplasts that were incubated in the light and those that were kept in the dark if any?

8. What is the function of each of the tubes in this experiment?