What is the role of water in the light reactions of photosynthesis?

The rol of water in photosynthesis is to supply electrons for said redox reactions, that is, water intervenes as a source of electrons

Explanation:

Since the water molecule is a very weak reducing agent, its electrons must be energized by the photons of sunlight, so that they acquire enough potential to reduce the inorganic molecules mentioned carbon, nitrogen and sulfur. The energetization of water electrons is carried out thanks to chlorophyll, the typical green pigment of the plant world that acts as a receptor and converter of solar energy into chemical energy.

In addition to redox energy, most of the assimilation reactions of C, N and S require the energy input of ATP (adenosine triphosphate), the well-known energy currency of living beings. Therefore, the energy of the photons absorbed by chlorophyll is used not only to energize electrons in water, but also to make ATP from inorganic phosphate. This last reaction is known as photophosphorylation and is catalyzed by the ATP synthetase of the thylakoid membranes. Thus, photosynthesis can be considered to consist of two distinct and sequential phases. In the first place, the photooxidation of chlorophyll-dependent water, with the consequent production of assimilative power (high energy electrons and ATP), and secondly the assimilatory reduction of the primary bioelements thanks to the assimilatory power obtained in the previous phase