.png){kind=link}
The light-independent stage does not require sunlight and thus takes place at all times, given there is enough ATP.
Carbon Fixation...
The process of converting inorganic carbon (CO2) to organic compounds (Glucose, C6H12O6). This takes place during photosynthesis in the fluid, or the stroma of chloroplasts. This is a cyclical process, called the Calvin Cycle. 6 turns of the cycle are required to produce one molecule of glucose.
Stages of the Calvin Cycle...
The carbon from a molecule of CO2, marked as 1C at the top left of the cycle, goes through the process to exit at the bottom left of the cycle as a free, organic carbon molecule. (Process described below.)
Underlined things you need to memorize, the rest you need to understand.
1. Carbon Fixation...
Carbon dioxide (1C) combines with the 5C sugar Ribulose bisphosphate (RuBP) to give two 3C molecules, glycerate 3 phosphate (GP).
Equation:...
Carbon dioxide (1C) + Ribulose bisphosphate (5C) = 2 x Glycerate 3 phosphate (3C)
CO2 + RuBP = 2GP
This reaction is catalyzed by the enzyme ribulose bisphosphate carboxylase (rubisco), which is the most common enzyme found in green plants.
2. Reduction...
GP, in the presence of ATP and NADPH, is reduced (loses electrons) to TP (a less stable molecule.)
Equation:...
2xGlycerate 3 phosphate (3C) + ATP/NADPH = 2xTriose phosphate (3C) (+ADP/NADP)
2GP + ATP/NADPH = 2TP
3. Synthesis of Glucose...
From the two TP molecules (6C), one carbon is released to form glucose. The other five carbons are needed to produce Ribulose biphosphate.
The remaining two TP molecules (one no longer a tp molecule as it has lost a carbon), join together to form RuBP, converting 3 ATP to ADP.
Glucose has 6 carbons, thus 6 instances of the cycle must complete to for a glucose molecule.
Final Equation...
| 3 | CO2 | \ | |
|---|---|---|---|
| 12 | NADPH | = | 1 Glucose |
| 18 | ATP | / |