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Jim Bidlack - BIO 1304
GENERAL BOTANY
Lecture 10 -
Photosynthesis (Part II)
IV.
(Continued from last time) Dark reactions
A.
Major purpose - use energy from light reactions to fix CO
2
into organic molecules
B.
Reagents of dark reactions
1.
ATP and NADPH
2.
CO
2
3.
Ribulose bisphosphate
4.
Enzymes (especially RUBISCO - Ribulose bisphosphate carboxylase / oxygenase)
C.
Why fix CO
2
?
1.
Store and use chemical energy in the form of organic compounds
D.
Steps of CO
2
fixation:
1.
CO
2
and H
2
O (1 carbon) are added to ribulose bisphosphate (5 carbons) to form two
molecules of 3-phosphoglyceric acid (3-PGA) (total of 6 carbons)
2.
Catalysis of this reaction by RUBISCO
3.
3-PGA is reduced to 3-PGAL with the help of NADPH and ATP
4.
3-PGAL is converted to either fructose diphosphate or, eventually ribulose bisphosphate
5.
Fructose diphosphate goes to other aspects of metabolism and ribulose bisphosphate goes
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- Fall '10
- Bidlack
- Botany, Photosynthesis, Organic Molecules, Ribulose Bisphosphate Carboxylase, CO2 fixation
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