1. Light Independent Reactions
Occurs in the stroma and converts carbon dioxide to carbohydrates using energy from ATP and NADPH
CO2 must be converted to organic compounds (this is called CO2 assimilation) – this is done in the
light independent reaction
Carbon Fixation
Regeneration of
RuBP
Reduction
Ribulose 1,5-bisphosphate

2. 1. Carbon Fixation CO2 + RuBP  unstable C6  2 PGA
CO2 bonds to a pre-existing molecule in the stroma (Ribulose 1,5-bisphosphate… aka RuBP)
The resulting 6 carbon intermediate quickly changes to 2 three-carbon molecules of 3-phosphoglycerate (PGA)
This is catalyzed by Ribulose bisphosphate carboxylase (Rubisco) - possibly the most abundant protein on earth

3. 2. Reduction
The new PGA is phosphorlated by ATP and then reduced by NADPH creating Glyceraldehyde-3-phosphate
Some G3P goes on to make glucose and other carbohydrates
Most G3P goes on to replenish RuBP

4. 3. Regenerating RuBP
Energy, supplied by ATP is required to break and reform bonds to make the 5 carbon RuBP
The Calvin cycle must be completed 6 times in order to synthesize one molecule of glucose.
Of 12 G3P molecules that are produced in 6 cycles 10 are used for regeneration of RuBP, and 2 are used to produce one glucose molecule.
Net equation is :
6 CO ATP NADPH + water  3 G3P Pi + 18 ADP + 12 NADP+

5. Glyceraldehyde-3-phosphate
Is used to produce:
Glucose
Sucrose
Cellulose
Oils
AAs (along with nitrogen)