Question

Differentiate between cyclic and non-cyclic photophosphorylation.

Answer 1

	Cyclic photophosphorylation	Non-cyclic photophosphorylation
1.	Only Photosystem I is involved.	Both photosystems I and II are involved.
2.	The electron given out by PS-I returns.	The electron given out by PS-II does return to it, but is used up by PS-I.
3.	It is not associated with the photolysis of water, and so, oxygen is not liberated.	It is associated with the photolysis of water and the liberation of oxygen.
4.	It involves only ATP synthesis.	It involves ATP synthesis and production of NADPH2.
5.	It takes place under low light intensity, anaerobic conditions, or when CO2 availability is less.	It takes place under optimum light, aerobic conditions and the presence of CO2.
6.	It does not participate in photosynthesis except in some bacteria and C4 plants.	It is concerned with CO2 fixation in all plants.