If the Calvin cycle stopped working, the concentrations of ATP, NADPH, and sugars would be affected as follows:
- ATP and NADPH concentrations would increase: The Calvin cycle consumes ATP and NADPH produced by the light-dependent reactions to fix carbon dioxide and synthesize sugars. If the Calvin cycle stops, ATP and NADPH would no longer be used in the reduction and regeneration steps, causing their concentrations to build up since they are still produced by the light reactions but not consumed
- Sugar concentrations would decrease: The Calvin cycle is responsible for converting carbon dioxide into glyceraldehyde-3-phosphate (G3P), a three-carbon sugar that is the precursor for glucose and other carbohydrates. Without the Calvin cycle functioning, sugar synthesis would halt, leading to a drop in sugar levels in the plant cells
In summary, a halted Calvin cycle leads to accumulation of ATP and NADPH due to lack of consumption, and a decline in sugar production because carbon fixation and sugar synthesis cease.
