Photosynthesis and Artificial Photosynthesis

Photosynthesis and
Artificial Photosynthesis
Qi Huijie
Institute of Precision Engineering
The Chinese University of Hong Kong
26/06/2007
http://www.ipe.cuhk.edu.hk/
Natural Photosynthesis
Photosynthesis is the process whereby green plants
fix gaseous carbon to form carbohydrates using light
Energy.
Light
6H2O + 6CO2 ----------> C6H12O6+ 6O2
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Photosynthesis almanac
1648 : Van Helmont
1771: Priestley
1818: Pierre Joseph Pelletier and Joseph Bienaimé Caventou name the
green pigment in plants chlorophyll
1864: von Sachs and Pfeffer show that starch is a by product of photosynthesis
1880: Theodor Wilhelm Engelmann recognises that photosynthesis takes
place inside the chloroplasts.
1897: Photosynthesis
…
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Nobel Prize on Photosynthesis
The Nobel Prize in Chemistry 1961: "for his research
on the carbon dioxide assimilation in plants"
Melvin Calvin
The Nobel Prize in Chemistry 1988:
"for the determination of the three-dimensional
structure of a photosynthetic reaction centre“
Hartmut Michel, Johann Deisenhofer and
Robert Huber
The Nobel Prize in Chemistry 1997: “for their elucidation of
the enzymatic mechanism underlying the synthesis of
adenosine triphosphate (ATP)"
Paul D. Boyer and John E. Walker
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Mechanism of photosynthesis
?
Does light is needed in all processes of photosynthesis?
Photosynthesis consists of two processes:
1. Light Reactions (require light)
2. Dark Reactions or the "Calvin Cycle" (do not require light)
H2O
Light
Light
Reaction
O2
ADP
ATP
NADPH
NADP
CO2
Dark
Reaction
organic
compound
H2O
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Chloroplast and Pigments
NADP
+
ADP
P
+
Calvin
Cycle
LightReaction
ATP
NADPH
Chloroplast
Pigments:
Chlorophyll-a, -b
Carotenoids
Xanthophylls
Phycobilins (cyanobacteria)
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The Light Reactions
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The Light Reactions
photosynthetic chain
(Z scheme)
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The Light Reactions
Photophosphorylation (ATP)
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The Dark Reactions-- Calvin Cycle
CO2+C5→2C3（fix CO2）
2C3→（CH2O）+ C5
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Photosynthesis (Review)
hv
6H2O + 6CO2 ----> C6H12O6+ 6O2
H20→H+ O2（split of water）
NADP+ + 2e- + H+ → NADPH（transfer H+）
ADP→ATP （energy transfer）
CO2+C5→C3（fix CO2）
C3→（CH2O）+ C5（organic compound)
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Artificial Photosynthesis – Deriving Energy from
Sunlight and Water
Sources of Energy on the Earth
Rates of Energy Flux
•
•
•
Solar Radiation
Geothermal energy
Gravitational energy
120,000 units/yr
30 units/yr
3 units/yr
Solar radiation-- 99.97% of energy on Earth
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Artificial Photosynthesis – Deriving
Energy from Sunlight and Water
Photosystem II (PSII)
Three basic parts of photosynthetic water
splitting:
1. light-harvesting molecule- chlorophyll (P).
2. tyrosine- mediates electron transport and
catalyses the reaction.
3. Mn complex - sends electrons to chlorophyll,
forming an active surface for water splitting.
Artificial Photosynthesis: Deriving energy from
sunlight and water
THE SWEDISH ENERGY AGENCY. 2003.
www.stem.se
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Model of Artificial Photosynthesis
Photosensitizer
Simulation:
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Great expectations:
life-giving oxygen in one end, and powerful
hydrogen fuel in the other.
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