Quiz 9: Photoinduced Proton Transport Through Chloroplast Membranes

Chemistry

In this problem, we are asked to draw a flow chart for the chloroplast preparation steps in this experiment. The isolation steps require a series of steps, mostly involving centrifugation at various speeds, and then several chemical isolation steps to select just for the chloroplasts. The flow chart would be as follows: img Thus, chloroplasts can be isolated from leaf extracts.

In this problem, we are asked to explain chlorophyll extraction in terms of chemistry, explaining why acetone is a better solvent for the extraction, and what steps could be taken to improve the yield in the extraction step. Chlorophyll, as an organic molecule, is largely non-polar, and therefore is more soluble in non-polar solvents such as acetone; acetone will disrupt the pigment-protein complex as well. To improve yield, we could combine multiple extractions into a larger starting pool; this would require more starting material (leaves).

In this problem, we are asked to describe another method for determining the rate of adenosine triphosphate (ATP) generation during the photophosporylation process. ATP is creating by recycling adenosine diphosphate (ADP) that is created when ATP is used to power functions in the plant. The reaction involves joining an inorganic phosphate molecule back onto the ADP to create ATP. Thus, we can watch for the uptake of inorganic phosphorus using radioactive 32 P. We could also use a colorimetric measurement to monitor changes in non-radioactive phosphorus concentrations.