When sunlight bathes the chloroplast, and photons are absorbed
The energys transduced so fast that food is quickly stored,
Photosynthetic greenery traps light the spectrum through
Then dark pathway machinery fixes the CO2
Two chlorophyll;s (a,b to you) are cleverly deployed
In photosystems I and II, within the thylakoid
System I takes energy, at 700 (red)
While system II (with pigment b ) takes 680 instead.
At manganese on center II, see oxygen displace
As waters split, and protons too, leave membrane inner face
Electrons that we thus produce, cross, photo-fortified
Plastoquinone then to reduce, upon the other side.
Meanwhile at I, chlorophyll a is photo-oxidized
(At positive holes, formed that way, electrons are much prized),
Electrons that we thus eject reduce NADP
With ferredoxin we suspect, as intermediary.
The hole in I we now negate, plastoquinol moves in
With b and f to mediate, and plastocyanin,
That redox loop, potential large, runs exergonically
With membrane-separated charge, and thence to ATP
That Z track by electron pair, reduced NADP,
Plucked oxygen from waters care, and made some ATP.
Now weve got power to reduce, and ATP to spare,
Food in the dark we can produce, from CO2 in air.
Ribulose bisphosphate takes, a mole of CO2
Gives two 3-phosphoglycerates, (if Calvins storys true)
NADPH now provides, reducing power to make
Two phosphoglyceraldehydes (as ATP we break)
There now occurs a jolly jig (the details well ignore)
With carbon chains both small and big, to ribulose once more,
Each time round, as CO2, is fixed weve chains to spare
And we can make hexoses new, from triose phosphate pair.
Other routes involve C4, or pyruvate to fat,
NADPH as before, is vital still for that,
ATP still provides the drive, the moral still is this &emdash;
The one thing that keeps life alive is photosynthesis.