Photosynthesis--The Photo Part

Your book is really quite good in this half of photosynthesis. It covers the history of discovery and the photo-electronic-chemi-osmotic processes involved in the so-called "light reactions." You should read it closely.

I think the parallelisms between respiration and photosynthesis were worthy of emphasis, so here is an over-simplified diagram... (you might have to widen your Netscape window to see this correctly).

RESPIRATION:
        ____________                _____________            _______________
       | glycolysis |              | Krebs cycle |--> CO2   | ETS & Ox Phos |
sugar -|------------|--> pyruvate -|-------------|--> NADH -|---------------|--> H2O
       |  cytosol   |              | mito matrix |          | mito inner mem|<-- O2
       |____________|              |_____________|          |_______________|==> ATP!!                                                 \-->ATP

PHOTOSYNTHESIS:
          _____________              ______________             __________________
         | sucrose syn |            | Calvin cycle |           | Light React & PP |<=== LIGHT!!
sugar <--|-------------|- triose <--|--------------|- NADPH <--|------------------|<--H2O
         |  cytosol    |            |chloro stroma |<-- ATP <--| chloro inner mem |\-->O2
         |_____________|            |______________|<-- CO2    |__________________|

You should be able to reproduce those basic relationships between these two processes. You should be aware of the fundamental arrow-direction differences, and the three distinct phases shared by the two reaction pathways.

Glycolysis and sucrose synthesis are both enzymatic processes occuring in the cytosol. They involve the structural relationship between a half-sugar and a whole sugar.
The Krebs and Calvin cycles are a cyclic set of enzymatic reactions occuring in the cytoplasm of an endosymbiont (organelle internal liquid) and process carbon as carbon dioxide.
The light reactions and electron transport chain are electronic in function, using a set of membrane-bound carriers. These carriers are heme-iron and quinone/polyphenol electron/proton handlers. They pump protons across the inner membrane to conserve energy. That energy is trapped in ATP as the protons are leaked back into the cytosol of the endosymbiont.

This comparative diagram shows grossly simplified comparisons:

Respiration:
CH₂O + O₂ --> CO₂ + H₂O + ATP

Photosynthesis:
CO₂ + H₂O + light --> CH₂O + O₂

The two reaction systems are basically the reverse of each other. One undoes the other in plants. Since plants do not eat to supply their energy needs, the plant must do enough photosynthesis to meet its needs for maintenance, growth, and reproduction while compensating for losses due to respiration both night and day.

The light reactions

We went on to talk about the light reactions in more detail. As your book covers this well here, I mostly used book diagrams, except for this one:

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