What is the difference beyween photosystem 1 and photosystem 2?

Answer 1

The structure of photosystem I in a cyanobacterium ("blue-green alga") has been completely worked out. It probably closely resembles that of plants as well. It is a homotrimer with each subunit in the trimer containing: * 12 different protein molecules bound to * 96 molecules of chlorophyll a ** 2 molecules of the reaction center chlorophyll P700 ** 4 accessory molecules closely associated with them ** 90 molecules that serve as antenna pigments * 22 carotenoid molecules * 4 lipid molecules * 3 clusters of Fe4S4 * 2 phylloquinones Photosystem II is also a complex of * > 20 different protein molecules bound to * 50 or more chlorophyll a molecules ** 2 molecules of the reaction center chlorophyll P680 ** 2 accessory molecules close to them ** 2 molecules of pheophytin (chlorophyll without the Mg++) ** the remaining molecules of chlorophyll a serve as antenna pigments. * some half dozen carotenoid molecules. These also serve as antenna pigments. * 2 molecules of plastoquinone

Source: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/LightReactions.html

Answer 2

Photosystem I (PS I) functions in the production of NADPH and plays a role in cyclic photophosphorylation. Photosystem II (PS II) is involved in water splitting and the initiation of linear electron flow in the light-dependent reactions of photosynthesis. In summary, PS I is primarily involved in reducing NADP+ to NADPH, while PS II is involved in generating ATP and the oxygen released during photosynthesis.