Chloroplasts and the light-dependent stageEdexcel A-Level Biology B: Mind map

Exam questions on Chloroplasts and the light-dependent stage

1. Palisade mesophyll cells of a leaf were examined with an electron microscope. Each chloroplast was about 5 µm long, was bounded by two membranes, and contained stacks of flattened membrane sacs joined to one another and surrounded by a fluid.
   Explain how the structure of the grana adapts the chloroplast for the light-dependent stage.2 marks
2. In the thylakoid membranes of a chloroplast, light energy excites electrons in chlorophyll a. The excited electrons pass along a chain of electron carriers. In non-cyclic photophosphorylation the electrons are finally accepted by NADP.
   Explain how the movement of electrons along the chain leads to the production of ATP.2 marks
3. A herbicide binds to the first electron carrier of the electron transport chain in thylakoid membranes, so that electrons can no longer pass from chlorophyll to the carrier. Isolated chloroplasts treated with the herbicide were illuminated in a solution containing ADP, phosphate and NADP.
   Explain why no oxygen is released from the treated chloroplasts.3 marks