OXYGENIC PHOTOSYNTHESIS - ELECTRON-TRANSFER IN PHOTOSYSTEM-I AND PHOTOSYSTEM-II

Photosystems I and II drive oxygenic photosynthesis. This requires bio chemical systems with remarkable properties, allowing these membrane-b ound pigment-protein complexes to oxidise water and produce NAD(P)H. T he protein environment provides a scaffold in the membrane on which co factors are placed at optimum distance and orientation, ensuring a rap id, efficient trapping and conversion of light energy. The polypeptide core also tunes the redox potentials of cofactors and provides for un idirectional progress of various reaction steps. The electron transfer pathways use a variety of inorganic and organic cofactors, including amino acids. This review sets out some of the current ideas and data o n the cofactors and polypeptides of photosystems I and II.