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Photosynthesis

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Photosynthesis

Postby PPonte » Thu May 04, 2006 7:45 pm

The removal of electrons from water molecules and their transfer to NADP+ requires energy. The electrons are moving from a redox potential of about +0.82 volt in water to −0.32 volt in NADPH. Thus enough energy must be available to move them against a total potential of 1.14 volts. Where does the needed energy come from? The answer: Light.


Could someone explain me the text in bold, please? Thank you.

~PP
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Postby kiekyon » Fri May 05, 2006 1:15 am

First the energy in the light is captured by special proteins called light harvesting complexes or antennae. These special proteins contain pigments like chlorophyll which can capture the energy of photons (the particles that make up light). The light energy is converted into electrical energy (electrons moving through proteins that act like wires). This energy is funnelled into an important protein complex called the reaction center. Here some chemistry takes place and an electron is given a lot of energy and becomes excited. This special electron comes from water. When water is split into hydrogen and oxygen, an electron can be captured and excited by the electrical energy from the light harvesting complexes. The splitting of water is how photosynthesis produces the oxygen we breath

OK. So now we have an excited electron in the reaction center. This electron can be thought of as water at the top of a waterfall. As the electron becomes less excited, it releases some energy. Just as water loses energy as it falls from the top of a waterfall. The little bits of energy released are captured by another set of proteins. These convert the electrical energy of the excited electron into chemical energy. The chemical energy takes the form of high energy chemical bonds in things like ATP and NADPH.

:roll:
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Postby PPonte » Sat May 06, 2006 9:54 pm

Thank you very much for your explanation. :D

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Postby SilverXIII » Thu May 11, 2006 11:59 am

O wow. Hi :P Im a grade 11 student.. Just recently interested in Biology so i dont know much :P

All i've ever learnt was that the light hits the plant, which activates the chlorophyll. (Is it in this stage that the electron starts getting excited and split the H2O ?)

I've also learnt about the NADP which picks up the 4H and the ATP. Where does the NADP come from, or is it already a carrior molecule which already exists in the plant? (btw what does it stand for?)
... If you think about it.
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Postby kiekyon » Fri May 12, 2006 8:56 am

SilverXIII wrote:
Where does the NADP come from, or is it already a carrior molecule which already exists in the plant? (btw what does it stand for?)


NADP=nicotinamide adenine dinucleotide phosphate :wink:
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Postby SilverXIII » Sat May 13, 2006 4:39 am

oh my god... its so long and hard to remember..

Hope they dont ask us that in the HSC <,<
... If you think about it.
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