Question

!!! Three Medal Question !!!

- Summarize what happens during the light reactions of photosynthesis.

- What happens during the carbon fixation step of the Calvin cycle?

- During which stage of photosynthesis is glucose made?

Answer 1

1. light strikes photosystem 2, exciting the electrons. The electron come from a water molecule that has been split into hydrogen and oxygen. That is the first reactant (water), and Oxygen gas is given off as the first product. The excited electrons then travel down a short electron transport chain, and while doing so they pump H+ molecules (hydrogen molecules) into the inner thylakoid space across the thylakoid membrane from the stroma. The electrons are then passed, at the end of the transport chain, to photosystem 1, where they are re-excited by light. The electrons are passed down another short electron transport chain, which pumps a few more H+ into the thylakoid space, then the electrons get passed to a molecule of NADP+, which is reduced to NADPH. NADPH is a product, NADP+ a reactant. The H+ in the thylakoid then diffuse back into the stroma through a molecule of ATP Synthase that is a channel through the memebrane of the thylakoid. As they pass through the ATP synthase, the H+ make the ATP Synthase go into it's active conformation so it is able to turn ADP into ATP. ADP is a reactant, ATP is a product. To sum it all up, H20, NADP+, and ADP are reactants, and oxygen, NADPH, and ATP are products.