How do the light-dependent reactions proceed?
The form of photosynthesis with which we are most familiar is non-cyclic photophosphorylation. It consists of two sets of pigments to excite. They are called PS1, or photosystem 1, and PS2, or photosystem 2. PS1 is better excited by light at about 700 nm, and is thus sometimes called P- 700. PS2 cannot use photons of wavelength longer than 680 nm, and is thus sometimes called P- 680. Energy enters the system when PS2 becomes excited by light. Electrons are shed by the excited PS2 (oxidation), which grabs electrons from water, producing a molecule of oxygen gas for every two waters split. PS2 thus returns it to its unexcited state (reduction) . The electrons are passed through a chain of oxidation-reduction reactions.
