Carbon Fixation Flashcards
Carbon fixation is a ___ reaction.
Dark
Function of Carbon Fixation
Use NADPH and ATP to fix carbon dioxide and make glyceraldehyde-3-phosphate
Stage 1
Carbon fixation
CO2 fixation catalyzed by the enzyme Rubsico
Product of Stage 1
3-phosphoglycerate
Most abundant protein in humans
Collagen
Most abundant protein in plants
Rubisco
Rubisco
Ribulose 1,5-bisphosphate carboxylase-oxygenase
Has 16 subunits (8 large & 8 small)
Less efficient enzyme
kcat (turnover #) ≈ 3 s-1
Stage 2
Reduction
Glyceraldehyde-3-phosphate (G-3-P) is the main product of Calvin cycle
Stage 3
Regeneration of acceptor
What enzymes are regulatory enzymes?
Phosphoribulokinase
Ribulose bisphosphate carboxylase
Fructose bisphosphatase
Sedoheptulose bisphosphatase
High Km
Can take more substrate
Low Km
Saturated at low levels of substrate
The Calvin Cycle occurs in the ____
Stroma
Conditions that increase activity of Rubisco
Light
Higher Mg2+ concentration
Higher pH
What enzyme activates Rubsico?
Rubisco activase
Rubsico is ____ at night
Inactive
Rubisco is inhibited by:
CA1P (2-carboxyarabinitol-1-phosphate), which is produced in the dark
Four Calvin cycle enzymes and Rubsico activate are regulated by _____
Light-dependent reduced ferredoxin
Rubisco, which fixes CO2, also reacts with ____ to produce a metabolically useless product
O2
What is the product of a reaction between Rubsico and O2?
2-phosphoglycolate
Salvaging 2-phosphoglycolate is costly. This pathway is called _____
Photorespiration
In C4 plants (corn), CO2 fixation and Rubisco activity are _____
Spatially separated
CAM (Crassulacean Acid Metabolism) plants are adopted to drought
Acidity of vacuole builds up at night as reaction proceeds
Dark: Stomata open
Light: Stomata closed
