Download 1. Background and overview of photosynthesis: cell structure

1. Background and overview of photosynthesis:


cell structure: Eucaryotic (plants and algae) vs Procaryotic (cyanobacteria, and the purple
and green photosynthetic bacteria).
evolution of O2:
o oxygenic photosynthesis (eucaryotes, cyanobacteria).
o anoxygenic photosynthesis (purple and green photosynthetic bacteria, and
heliobacteria).
Two Phases of Photosynthesis: Fig. 20.2


light reactions:
o In oxygenic photosynthesis ATP and NADPH synthesized.
o In anoxygenic photosynthesis ATP is primary product.
dark reactions:
o 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.
2. Light Harvesting pigments and their organization



Chlorophyll/bacteriochlorophyll: Fig. 20.3
o Structure.
o adsorption spectrum of different chlorophylls/bacteriochlorophylls.
o How do the purple and green photosynthetic bacteria differ from the
cyanobacteria with respect to their light harvesting pigments?
light harvesting pigments: two structual types
o isoprenoids- used primarily to prevent photooxidation of photosynthetic system.
Fig. 20.8 and 20.9
o tetrapyrroles (primary light harvesting pigments). Two classes
 bile pigments (phycobiliproteins). Fig. 20.10
 porphyrins (heme group of cytochromes, chlorophyll and
bacteriochlorophyll).
Location and organization of photosynthetic apparatus:
o Arrangment of light harvesting pigments Reaction center. Fig. 20.6
 Phycobilisomes. Fig. 20.10
o Organization of photosynthetic apparatus Eukaryotes: The chloroplast Fig. 20.5
 cyanobacteria- special unit membrane bound sacs called thykaloids. What
is the role of the phycobilisomes on surface of thylakoid?
 purple- invaginations of the cytoplasmic membrane.
 green- chlorosomes. Fig. 20.7 What is role of baseplate component?
 heliobacteria- photosythetic apparatus is integral to the cytoplasmic
membrane.
3. Anoxygenic Photosynthesis: Fig. 20.14, 20.15, 20.18
o
o
o
components of photosystem.
cyclic photophosphorylation.
generation of reducing power.
4. Oxygenic photosynthesis- Fig. 20.19
o
o
components of photosystem I. Used primary to generate reducing power, but can
be use to generate ATP by cyclic phosphosphorylation.
components of photosystem II. Used to generate ATP by noncyclic
photophosphorylation (also known as the "Z" scheme of photosynthesis).
5. Dark Reactions: CO2 fixation.
o
o
CO2 fixation by Calvin Benson Cycle. Fig. 20.22
 Amount of ATP and NADPH required.
 Key enzymes of pathway- ribulose bisphosphate carboxylase and
phosphoribulokinase.
CO2 fixation by Reverse TCA cycle and Hydroxypropionate pathway Fig. 20.24