Question

Describe the main chemical changes which occur during photosynthesis in a light reaction.

Answer 1

The light reaction occurs in two main steps:

1. Photolysis of water: The presence of light energy causes the water to separate.
   \[\ce{H2O ->[Sunlight][Chlorophyll]H+ + OH-}\]
   The OH⁻ groups combine to generate water, oxygen, and electrons.
   \[\ce{2(OH^-) - 2e -> 2(OH)}\]
   \[\ce{2(OH) -> H2O2}\]
   \[\ce{2H2O2 -> 2H2O + O2↑}\]
2. Reduction of NADP: The reduction of NADP molecules to NADPH₂ occurs through the action of H⁺.
   \[\ce{2NADP + 4e- + 4H- ->[enzyines] NADPH2}\]
3. Formation of ATP: In the presence of light, ADP combines with inorganic phosphate. ATP.
   \[\ce{ADP + iP -> ATP}\]