The Light Reaction Created by Caitlynn Lied 2008 NADPH NADP+ ATP NADPH NADP+ ADP H O H H O H H O H ATP.

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The Light Reaction Created by Caitlynn Lied 2008 NADPHNADP+ATPNADPHNADP+photosynthesisADPHOHADPADPHOHHOHATPATP

HHHHPhotosystem IPhotosystem IISunlight filled with photons shines onto the plantThe photons excite the electrons in the chlorophyll moleculesStromaThylakoid SpaceThe electrons move to the outer energy levelsAs the electron moves from an excited state (high energy) to ground state (low energy), the difference in energy is passed to a neighboring chlorophyll molecule.HHH2

HHHHPhotosystem IPhotosystem IIThylakoid SpaceStromaThe last chlorophyll molecule that the energy reaches is called the reaction center (also called P680 chlorophyll)The molecule becomes so energized that it throws off its electron, which is accepted by the Primary Electron Acceptor (PEA)

The energy continues to move to every chlorophyll molecule in the photosystemHHH

HHHHPhotosystem IPhotosystem IIThylakoid SpaceStromaWhile energy was being passed in Photosystem II, the same was happening in Photosystem IThe PEA moves along a pathway known as an Electron Transport Chain to Photosystem I. Passing along a H pump. NOTE: The reaction center in Photosystem II is called P680, but its called P700 in Photosystem I- the difference is in what type of wavelength the molecule absorbsHHHThe electron from the first PEA then replaces the one lost in Photosystem I

Photosystem IIHHHHThe O2 molecule leaves the plant, and the H+ moves off to a latter part of the cyclePhotosystem IStromaThylakoid Space2H2O molecules split to produce 4 hydrogen ions, 1 oxygen gas molecule, and 4 electrons. These electrons replaces the ones lost in the reaction center in Photosystem IIAs the PEA traveled along the E.T.C, energy from the electron was used to actively transport a hydrogen ion from the stroma into the thylakoid spaceHHHHHHOHO

At this point, the reaction no longer needs Photosystem IIHOHHOHPhotosystem IIPhotosystem IHHHHHStromaThylakoid SpaceHHHHHH

HPhotosystem IStromaThylakoid SpaceHOHHOHHHHHHHHNADPHNADP+Now, NADP+ enters the NADP Reductase from the dark reactionThe electron from the PEA and a Hydrogen Ion from the stroma combine with the NADP+ to form one NADPHThen the NADPH leaves to go back to the dark reactionH

HOHHOHPhotosystem IHHStromaThylakoid SpaceHHADPAfter that, ADP and a phosphate (also from the dark reaction) enters the ATP SynthaseThe ATP Synthase pumps the H+ (originally from H2O) to the stroma through passive transport As H+ passes through the membrane, enough energy is supplied to combine an ADP + P to form one ATP molecule. HHHHATPThen the ATP moves back to the dark reactionAnd thats the light reaction!

Photosystem IPhotosystem IIHOHNADPHNADP+ADPATP

Molecule template9


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