question archive These are the two key reactions in the process of converting light into sugars or other compounds
These are the two key reactions in the process of converting light into sugars or other compounds
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These are the two key reactions in the process of converting light into sugars or other compounds.
Plants and algae, as well as cyanobacteria, contain pigment centers that allow for the transfer of energy in the form of electrons. There are many types of pigment molecules found in this cells but the main types are in the form of chlorophylls. PS I is involved in mainly electron transfer and helps build NADPH. This is oxidation-reduction. Light hits the pigment center and causes the electrons to "jump" to the higher state but when they do, NADP picks them up. PSI works at 700nm and builds NADPH which can be used later in Calvin Cycle. PSII is a different reaction set and uses 680 nm. Again, electrons are excited but when they "jump" they enter an electron transfer chain that builds ATP. There is also a side reaction called photolysis. This reaction splits water to provide H+ and electrons that can replace those in PSI. PSII makes ATP while PSI makes NADPH+. See diagram:
