Question

you are a plant with water molecule that has just undergone photolysis. what happens to one of thr H atoms if used for the P680 pathway and winds up as part of a sugar molecule. Include: the location of each part of the process, and where the ATP is produced and needed within each pricess to build 1 sugar molecule

Answer 1

Special chlorophyll molecule P680 is used in photosystem II as photon is best absorbed at 680 nm. Photosystem II also contains chlorophyll b and other accessory pigments. P 700 is used in photosystem I

After PS I, electron is transferred thylakoid thereby creating an unstable P700+. This electron is provided by chlorophyll P680. During PS II, light hits P680, an electron is released and it reaches chlorophyll a P700. Chlorophyll a P700 accepts the electron and produce ATP through noncyclic phosphorylation

Ultimately chlorophyll a P680 becomes electron deficient. It thus oxidizes water to regain lost electrons.

2H2O→4H++4e−+O2

All the above proves takes place on the site of stroma.

Now, water oxidation takes place in the thylakoid lumen where cofactor OEC with 4 manganese (Mn) ions oxidizes and transfers the water electrons to P680+

[Mn4]4++2H2O→[Mn4]0+4H++O2

At the end of this reaction, 2 ATP and 9 NADPH and photolysis of water. 2 ATP and 9 NADPH will be used in the dark reactions.