Question

In an experiment, we measured the change in pH in solutions when exposed to light for sixty seconds, dark for thirty, light for thirty and then dark for thirty. We measured the pH every ten seconds. This was done for chloroplasts with no redox cofactor, chloroplasts with a redox cofactor, and chloroplasts with redox cofactor, ADP, and phosphate.

1. Why is the amount of chlorophyll kept constant in all experiments?

2. Explain the effect of the addition of ADP and phosphate on the rate of proton uptake.

3. Why does the pH of the suspension solution decrease during dark intervals?

4. Why is acetone used in the chlorophyll extraction procedure?

Answer 1

2)The addition of ADP and phosphates incrase the concentration of H⁺ clearly by seeing the following reaction.

2 H₂O + 2 NADP⁺ + 3 ADP + 3 P_i + light → 2 NADPH + 2 H⁺ + 3 ATP + O₂

3) For ATP synthesis we need light energy in dark we do not have light source so the concentration of H+ ion decreases.

4) The pigments and the rest of the leave stuff will just stick together in water. acetone is an organic solvent that can separate the aqueous impurities from the pigments in leaves.