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

CO2

Calvin Cycle C3

2 PGA (3C)

RuBP (5C)

rubisco

Bundle Sheath Cell

C4, Only an Addition to the Calvin Cycle

CO2

Pyruvate

C4 “Front End”

PEPcarboxylase

Malate (4C)

PEP (3C)

Mesophyll Cell

Malate(4C)

Pyruvate (3C)

OAA (4C)

ATP AMP + PP

Kranz AnatomyNot Grey’s AnatomyDefinitely Not This!!

C4 Isn’t about CO2 (sorta)

• Its all about water and temperature

CO2

Calvin Cycle

RuBP

rubisco

PGAPGO

O2

• 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 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