1. Classification of Photosynthetic Organisms by:

• cell structure: Eucaryotic (plants and algae) vs Prokaryotic (cyanobacteria, the purple and green photosynthetic bacteria, and the phototrophic heliobacteria).
• evolution of O₂:
  • oxygenic photosynthesis (eucaryotes, cyanobacteria).
  • anoxygenic photosynthesis (purple and green photosynthetic bacteria, and heliobacteria).

2. Two Phases of Photosynthesis:

• light reactions:
  • In oxygenic photosynthesis ATP and NAD(P)H synthesized.
  • In anoxygenic photosynthesis: In purple ATP is primary product, while in green-sulfur and eliobacteria can generate both ATP and NDH directly
• dark reactions:
  • fixation of CO₂ into cellular carbon. The majority of autotrophs (photoautotrophs, and chemoautotrophs) use the Calvin Benson Cycle (also known as the C₃ pathway or the reductive pentose cycle). Two other ways that CO₂ fixation can occur is by the reverse TCA cycle and the carbon monoxide pathway.

3. Light Phase.

• light harvesting pigments: two structual types
  • isoprenoids- used primarily to prevent photooxidation of photosynthetic system. Example being carotenoids found in most photosynthetic and some non-photosynthetic organisms Fig. 17.8
  • tetrapyrroles (primary light harvesting pigments). Two classes
    • bile pigments (phycobiliproteins). Fig. 17.10
    • porphyrins (heme group of cytochromes, chlorophyll and bacteriochlorophyll).
• Chlorophyll/bacteriochlorophyll: Fig. 17.3
  • Structure.
  • absorption spectrum of different chlorophylls/bacteriochlorophylls.
  • reaction center chlorophyll/bacteriochlorophyll.
  • How do the purple and green photosynthetic bacteria differ from the cyanobacteria with respect to their light harvesting pigments?
• Location of photosynthetic apparatus:
  • eucaryotes-
    • chloroplast (thylakoids, grana). Fig. 17.5
    • organization of light harvesting pigments.
  • procaryotes-
    • cyanobacteria- special unit membrane bound sacs called thylakoids. What is the role of the phycobilisomes on surface of thylakoid?
    • purple- invaginations of the cytoplasmic membrane. Fig. 17.12
    • green-sulfur- chlorosomes. What is role of baseplate component? Fig. 17.7
    • Heliobacteria- photosythetic apparatus is integral to the cytoplasmic membrane .
  • What is the relationship of the light harvesting pigments with reaction center bacterio/chlorophyll in each of these bacteria?
• Light Reactions:
  • anoxygenic photosynthesis- Fig. 17.14 and 17.15
    • components of photosystem.
    • cyclic photophosphorylation.
    • generation of reducing power.
  • oxygenic photosynthesis- Fig. 17.19
    • components of photosystem I. Used primarily to generate reducing power, but can be used to generate ATP by cyclic photophosphorylation.
    • components of photosystem II. Used to generate ATP by noncyclic photophosphorylation (also known as the "Z" scheme of photosynthesis).

4. Dark Phase.

• CO₂ fixation by Calvin Benson Cycle. Fig. 17.21 and 17.22
  • Amount of ATP and NADPH required.
  • Key enzymes of pathway- ribulose bisphosphate carboxylase and phosphoribulokinase.

revised 10/10/07