Transcript CO 2 - OpenWetWare

C4, PUMP IT UP!
Dr. Weise
C3, History of Discovery
• Andrew Benson
James Bassham
Melvin Calvin UC Berkley
• 1949 Discovered radioactive CO2
fed to algae first goes into PGA a
3 Carbon Compound
• Calvin solely won the Nobel Prize in Chemistry 1961
C4, History of Discovery
• Hugo Kortschak – Hawaiian
Sugar Planters Research Lab
• 1965 Radioactive CO2
fed to sugar cane first goes
into malate a 4 carbon
compound
• Got scooped by Hal Hatch and Rodger Slack
C4, History of Discovery
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•
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Hal Hatch and Rodger Slack Colonial Sugar Refining Co,
Brisbane
By 1969 had elucidated complete
pathway we know today
Was initially called the Hatch Slack
Pathway
C4, Only an Addition to the Calvin Cycle
C4 “Front End”
Calvin Cycle C3
ATP
PEP (3C)
CO2
AMP + PP
Pyruvate
PEP
carboxylase
CO2
OAA (4C)
Malate (4C)
Mesophyll Cell
Pyruvate (3C)
RuBP (5C)
rubisco
2 PGA (3C)
Malate(4C)
Bundle Sheath Cell
Kranz Anatomy
Definitely
This!!
Not
Grey’sNot
Anatomy
C4 Isn’t about CO2 (sorta)
• Its all about water and temperature
Calvin Cycle
• At high temperatures
rubsico gets sloppy
RuBP
• Catalyzes more
rubisco
oxygenations
PGA
PGO
• Plant looses carbon and
energy
CO2
O2
What About the Water?
• Plants have pores too, we call them stomata
• To let in CO2 plant must let out Water
C4
• C4 acts as a CO2 pump for the Calvin cycle
• C4 can be twice as efficient at conserving
water at higher temperatures
• PEP Carboxylase has a much higher
affinity for CO2 than rubisco allowing those
stomates to stay closed conserving water
• But there is a price……..High ATP usage