Photovoltaics and Photosynthesis.
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The light reactions of photosynthesis can be compared to the production of electricity by solar cells. This process is called photovoltaics. The electrons in the solar cell capture light energy and are boosted to a high energy level where they are accepted by the wire making up the electrical circuit. The electrons then do work, such as to run an electric motor. Then the electrons lost by the solar cell must be replenished. This is done by completing the electrical circuit. In photosynthesis the electrons lost by the pigments involved are replaced by splitting water.
Comparison between photovoltaics and simplest form of of the light reaction.
1. Low energy electrons in surface of photocell(left) and in photosystem(right)
2. Photons boost electrons to high energy level in photocell and in photosystem.
3. Electrons accepted by wire at photocell-wire junction(left) and by electron acceptor in light reaction)
4. Electrons passed along wire(4 left) to motor(5); Electrons passed (4 right)to hydrogen pump(5).
5. Motor turns producing mechanical energy(work) and heat(left). Hydrogen pump works to send H+ ions to the inside of the thylakoid and these are used to make ATP. Heat is given off as well.
6. The electrons having lost their energy(6) are sent to the photocell(left) and to the photosystem(right).
These replenish those lost by the photocell(left) and the photosystem(right).
pgd revised 2/17/01