C4, PUMP IT UP! Dr. Weise

C 3, History of Discovery Andrew Benson James Bassham Melvin Calvin UC Berkley 1949 Discovered radioactive CO 2 fed to algae first goes into PGA a 3 Carbon Compound Calvin solely won the Nobel Prize in Chemistry 1961

C 4, History of Discovery Hugo Kortschak – Hawaiian Sugar Planters Research Lab 1965 Radioactive CO 2 fed to sugar cane first goes into malate a 4 carbon compound Got scooped by Hal Hatch and Rodger Slack

C 4, 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

CO 2 Calvin Cycle C 3 2 PGA (3C) RuBP (5C) rubisco Bundle Sheath Cell C 4, Only an Addition to the Calvin Cycle CO 2 Pyruvate C 4 “Front End” PEP carboxylase Malate (4C) PEP (3C) Mesophyll Cell Malate(4C) Pyruvate (3C) OAA (4C) ATP AMP + PP

Kranz Anatomy Not Grey’s Anatomy Definitely Not This!!

C 4 Isn’t about CO 2 (sorta) Its all about water and temperature CO 2 Calvin Cycle RuBP rubisco PGA PGO O2O2 At high temperatures rubsico gets sloppy Catalyzes more oxygenations Plant looses carbon and energy

What About the Water? Plants have pores too, we call them stomata To let in CO 2 plant must let out Water

C4C4 C 4 acts as a CO 2 pump for the Calvin cycle C 4 can be twice as efficient at conserving water at higher temperatures PEP Carboxylase has a much higher affinity for CO 2 than rubisco allowing those stomates to stay closed conserving water But there is a price……..High ATP usage