Light-independent reaction detail: carbon dioxide reacts with ribulose bisphosphate (RuBP) to form two molecules of glycerate 3-phosphate (GP) catalysed by rubisco; ATP and reduced NADP reduce GP to triose phosphate; some triose phosphate regenerates RuBP in the Calvin cycle; some triose phosphate is converted to useful organic substances
The Calvin cycle uses carbon dioxide, ATP, and reduced NADP to build a small sugar molecule called triose phosphate. The plant then uses triose phosphate to make glucose, fats, and other organic compounds.
Formula
CO₂ + RuBP → 2GP (catalysed by rubisco)
Real World
Rubisco is the most abundant protein on Earth — every leaf on every plant contains it, and collectively it fixes roughly 100 billion tonnes of CO₂ per year, which is why deforestation directly reduces global carbon fixation.
Exam Focus
Learn the carbon accounting: RuBP is 5C, GP is 3C, triose phosphate is 3C — examiners frequently ask you to explain where the carbon atoms go.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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