Question

Q40.) Assume we add a chemical that blocks the reduction of NADP+ to NADPH at the end of the electron transport chain in the light dependent reactions of photosynthesis. What would happen to the rate of sugar production in the Calvin Cycle. Explain your reasoning.

Answer 1

electron transport chain occurs in the thylakoid membrane, the electron from the PSII is excited by photons and this electron moves through the electron transport chain and finally, it is used to reduce NADP+ to NADPH.

during the electron transport, H+ is pumped to thylakoid lumen which increases the concentration of H+ in the thylakoid lumen, creating an H+ gradient, which is used by ATP synthase to make ATP from ADP and Pi.

If the NADP+ cannot be reduced to NADPH, the electron transport cannot occur, because the proteins in the electrons transport chain will remain reduced. so H+ gradient cannot be generated, so ATP synthesis decreases.

NADPH and ATP are used as energy sources in the Calvin cycle.

if NADP+ cannot be reduced to NADPH, levels of NADPH and ATP decreases so rate ofsugar production in the Calvin cycle decreases.