Major Points
1. Photosynthesis converts light energy to carbohydrates
2. Two photosystems:
light => ATP + NADPH
3. ATP and NADPH used to convert CO2 to glucose
An Oxygen Atmosphere?
* The atmosphere of early Earth was very reducing
* Molecular oxygen (O2) was absent
* Evolution of photosynthetic bacteria introduced oxygen to the atmosphere
Photosynthetic Balance Sheet
12H2O + 6 CO2 ---> 6O2 + C6H12O6 + 6 H2O
The "Light Reaction"
* Occurs on the thylakoid membrane
* Generates ATP and NADPH
* What is NADPH?
* ATP is generated by transporting protons down a concentration gradient
Two Photosystems
* Used for distinct steps in photosynthesis
* Consist of 200 to 300 pigment molecules and one "reaction center"
chlorophyll
* Photons excite an electron in the chlorophyll
* The electron passes down an electron transport chain generating the proton
gradient and NADPH
Formation of ATP & NADPH
After Figure 7.2(g) of Starr & Taggart
Calvin-Benson Cycle
After Figure 7.9 of Starr & Taggart