So this is a reducing agent. I find it amazing that somehow photons of sunlight are used to create these sugar molecules or these carbohydrates. You are probably aware that plants need sunlight, water, and a home like soil to grow, but where do they get their food? While plants take in carbon dioxide through tiny pores located on their leaves, stems and flowers, they need specialized structures to gather water and move it up through their stems.
So this requires sunlight.
In the reduction of CO 2 , six carbon-carbon and six carbon-hydrogen bonds are 'made' thus accounting for the requirement of 12 reducing equivalents. But when you dig a little deeper, you'll see that this doesn't happen directly, that this happens through a bunch of steps that eventually gets us to the carbohydrate.
These pigments are arranged in the thylakoid membranes in clusters, along with proteins and electron carriers, to form light-harvesting complexes referred to as photosystems. Frey , P. Footnotes In the 'real world' of green-plant photosynthesis, the oxygen is 'lost' as phosphate, not water, in the glyceraldehyde-3-phosphate dehydrogenase reaction see here , a key step in photosynthesis where reducing equivalents enter the carbon skeleton see here.
Most plants use roots to pull water from the earth. The most important pigments are the green chlorophylls, but accessory pigments called carotenoids are also present, which are yellow or orange.
The short answer is the the six water molecules on the left-hand side come from CO 2 , as a by-product of reduction. And the second hugely important part is getting the oxygen. Plants, however, take in and use carbon dioxide gas for photosynthesis. Do you have source of that equation?
You just have this P there. The reaction shown in Eqn 7 is neither an oxidation nor a reduction, but a dehydration the dehydration of ethanol to ethylene. And if you remember from glycolysis, you might remember that this PGAL molecule, or this G3P-- same thing-- this was actually the first product when we split glucose in two when we performed the glycolysis.
Let me write that down. Thank you for your interest in this question. It gets oxidized by losing the hydrogen and the electron with it.