Question

why is water required for PS 2 but not PS 1

Answer 1

Answer:

Deleted profile

To split the water molecule in photosynthesis, you need very special complex, called OEC oxygen evolving complex (of WSC water splitting complex). The process is extremely complex and can not occur elsewhere. OEC is associated ONLY with PSII. For full function of OEC you need functioning PSII and because the electron extracted from water has to "travel" to its terminal acceptor NADPH you need also the PSI as the complex where (or very nearby for the purists) the electron ends up at the NADPH. See the Z scheme.

OEC can function only with PSII