Which hypothesis best explains the synthesis of ATP in chloroplast?
a)	Chemosynthetic hypothesis	b)	Chemiosmotic hypothesis
c)	Potential gradient hypothesis	d)	Redox gradient hypothesis

(b)

The chemiosmotic hypothesis explains the ATP synthesis mechanism. Like in respiration, in photosynthesis too, ATP synthesis is linked to the development of proton gradient across the membrane. This time these are the membranes of the thylakoid. There is one difference that in photosynthesis the proton accumulation is towards the inside of membrane, i.e., in the lumen. In respiration, proton accumulate in the intermembrane of the mitochondria when electrons move through the ETS (Electron Transport System)