A. Photosystem I & II = harvest light energy

• 1. Thousands of pigment molecules in thylakoid membranes
• 2. Absorption of photons raises energy level of pigment molecules

3. Pigment molecule returns to ground state when energy is released in the form of heat and electrons.
V. The "Z" Scheme
          B. Electron transport system
               1. Coupled with PS I & II
               2. Releases energy in steps 1. Photolysis = Water molecule is split to release 2 H+ + O- + e-
               2. e- => PSII + light energy => higher energy state
               3. electron transport => lower energy state + H+ pumped
               4. e- => PSI + light energy => higher energy state
               5. electron transport energy reduces NADP- to NADPH
               6. ATP synthesized via ATPsynthetase as H+ diffuses down gradient
II. Calvin Benson Cycle (C3 Photosynthesis)
• A. Chloroplast stroma
• B. 6 CO2 + 12 NADPH +18 ATP -> 1 C6H2O6 + 12 NADP + 18 ADP + 18 Pi + 6 H2O
• C. One complete cycle fixes one molecule of CO2
• 1. Six complete cycles fixes enough CO2 to make one molecule of glucose
• 2. RuBP = Ribulose Bisphosphate
• 3. PGA = Phosphoglycerate
• 3. PGAL = Glyceraldehyde phosphate

4. RuMP = Ribulose Monophosphate
II. Calvin Benson Cycle (C3 Photosynthesis)
          D. Ribulose bisphosphate Carboxylase (RuBP Carboxylase) "Rubisco"
               1. High CO2 -> 2 PGA
2. Photorespiration
                    a. High O2 -> 1 PGA + phosphoglycolate
                    b. phosphoglycolate -> PGA + CO2
                    c. 20-30 % of Carbon fixed is lost
III. Hatch & Slack (C4) Photosynthesis
          A. Spatial separation of initial CO2 fixation and C3 cycle
          B. Mesophyll Cells
               1. "normal" looking chloroplasts
               2. CO2 + pyruvate + NADPH + H+ + 2 ATP -> malate + NADP+  2 ADP + 2 Pi
               3. PEP carboxylate is insensitive to O2
          C. Malate transported to