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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 • • • 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
