Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway)

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway)

Processes affected by pCO2 Calvin cycle (Carbon reduction pathway) RuBP binds CO2 2) rapidly splits into two 3-Phosphoglycerate therefore called C3 photosynthesis

Processes affected by pCO2 Calvin cycle (Carbon reduction pathway) RuBP binds CO2 2) rapidly splits into two 3-Phosphoglycerate 3) catalyzed by Rubisco (ribulose 1,5 bisphosphate carboxylase/oxygenase) the most important & abundant protein on earth Lousy Km Rotten Vmax!

Processes affected by pCO2 Calvin cycle (Carbon reduction pathway) Reversing glycolysis converts 3-Phosphoglycerate to G3P consumes 12 ATP & 12 NADPH/glucose

Processes affected by pCO2 Calvin cycle (Carbon reduction pathway) Reversing glycolysis G3P has 2 possible fates 1) 1 in 6 becomes (CH2O)n 2) 5 in 6 regenerate RuBP

Processes affected by pCO2 5 in 6 G3P regenerate RuBP Basic problem: converting a 3C to a 5C compound feed in five 3C sugars, recover three 5C sugars

Regenerating RuBP Basic problem: converting a 3C to a 5C compound must assemble intermediates that can be broken into 5 C sugars after adding 3C subunit

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway) Rubisco must be carbamylated & bind Mg2+ to be active!

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway) Rubisco must be carbamylated & bind Mg2+ to be active! RuBP binds & inactivates uncarbamylated rubisco

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway) Rubisco must be carbamylated & bind Mg2+ to be active! RuBP binds & inactivates uncarbamylated rubisco Rubisco activase removes this RuBP (also CA1P)

Processes affected by pCO2 rubisco usually limits C3 -> limited by demand for CO2 Supply is limited by resistance to CO2 diffusion Boundary layer Stomatal: only one that can be adjusted Liquid phase

Processes affected by pCO2 rubisco usually limits C3 -> limited by demand for CO2 Supply is limited by resistance to CO2 diffusion Boundary layer Stomatal: only one that can be adjusted Liquid phase Demand is set by mesophyll, Stomata control supply

Processes affected by pCO2 Demand is set by mesophyll, stomata control supply Ci is usually much lower than Ca A vs Ci plots tattle on the Calvin cycle

Processes affected by pCO2 A vs Ci plots tattle on the Calvin cycle In linear phase rubisco is limiting When curves RuBP or Pi regeneration is limiting

Processes affected by pCO2 Currently Rubisco usually limits C3 plants Will increase plant growth until hit new limiting factor

Processes affected by pCO2 Currently Rubisco usually limits C3 plants Will increase plant growth until hit new limiting factor Free-Air CO2 Enrichment Experiments show initial gains, but taper off w/in a few years Now are limited by nutrients or water

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway) Carbonic anhydrase: used to increase Cp CO2

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway) Carbonic anhydrase: used to increase Cp CO2 First step in C4 photosynthesis: PEPcase fixes HCO3- also serves as CO2 sensor (mech unknown)

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway) Fatty acid synthesis

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway) Fatty acid synthesis Phosphoenolpyruvate carboxylase

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway) Fatty acid synthesis Phosphoenolpyruvate carboxylase: plants often form malate cf pyr from glycolysis Get more ATP/NADH

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle Fatty acid synthesis Phosphoenolpyruvate carboxylase: plants often form malate cf pyr from glycolysis Get more ATP/NADH lets cells replace Krebs intermediates used for synthesis First step in C4

Processes affected by pCO2 Pathways that use CO2 as substrate Calvin cycle (Carbon reduction pathway) Fatty acid synthesis PEP carboxylase Pyruvate carboxylase (&/or malic enzyme) gluconeogenesis

Processes affected by pCO2 Pathways that use CO2 as substrate Pyruvate carboxylase PEPcarboxykinase carbamoyl phosphate synthetase: pyrimidine synthesis & ornithine/urea cycle

Processes affected by pCO2 Pathways that use CO2 as substrate 2) Pathways that release CO2 photorespiration: glycine decarboxylase

Processes affected by pCO2 Pathways that use CO2 as substrate 2) Pathways that release CO2 photorespiration: glycine decarboxylase Respiration (+ malic enzyme)

Processes affected by pCO2 Pathways that use CO2 as substrate 2) Pathways that release CO2 Photorespiration Respiration (+ malic enzyme) CO2 Inhibits respiration at 3% No obvious effects at 700 ppm, yet biomass reduced

pathways that release CO2 Photorespiration Respiration Pentose phosphate shunt in cytosol or cp

pathways that release CO2 Photorespiration Respiration Pentose phosphate shunt in cytosol or cp Pyruvate decarboxylase in fermentation

Pathways that release CO2 Serine or Phosphatidylserine decarboxylase for ethanolamine, choline, etc synthesis

Pathways that release CO2 Serine or Phosphatidylserine decarboxylase for ethanolamine, choline, etc synthesis Aromatic Acid Decarboxylase for many precursors

Pathways that release CO2 Serine or Phosphatidylserine decarboxylase for ethanolamine, choline, etc synthesis Aromatic Acid Decarboxylase for many precursors Many more AA Decarboxylases

Processes affected by CO2 2) pathways that release CO2 3) transpiration & stomatal number