Final answer:
The Calvin Cycle's main function is to create glucose and other sugars from CO2 using the energy in ATP and NADPH produced in the light-dependent reactions of photosynthesis.
Step-by-step explanation:
The overall purpose of the Calvin Cycle is to convert atmospheric carbon dioxide into glucose and other sugars, which plants can use as an energy source. This process is a light-independent reaction of photosynthesis and occurs after the light-dependent reactions have captured sunlight and stored its energy in the form of ATP and NADPH. During the Calvin Cycle, the enzyme ribulose biphosphate carboxylase (RuBisCO) facilitates the fixation of CO2 into organic molecules. The cycle uses the energy from ATP and the reducing power of NADPH to produce Glyceraldehyde-3-phosphate (GA3P) molecules, which accumulate to form sugars like glucose.
In summary, it requires six turns of the Calvin Cycle to fix six carbon atoms from CO2. These turns use energy inputs from 18 ATP molecules (12 in the reduction phase and 6 in the regeneration phase) and 12 NADPH molecules in the reduction phase only. Once fixed, the carbon atoms are assembled into sugars, providing energy storage for the plant and contributing to the global carbon cycle.