How do ATP and NADPH function in the Calvin cycle?

• A. They provide energy and reducing power to convert CO2 into glucose
• B. They are wastes produced during photosynthesis
• C. They store genetic information
• D. They break down glucose

Answer: (A)

ATP and NADPH provide the energy and reducing power needed to turn inorganic carbon from CO2 into organic carbohydrate in the Calvin cycle. CO2 is fixed to form 3-phosphoglycerate, which is then phosphorylated by ATP and reduced by NADPH to glyceraldehyde-3-phosphate. The energy from ATP drives the phosphorylation steps and helps regenerate the CO2-accepting molecule RuBP, while NADPH supplies the electrons to reduce the carbon intermediates toward carbohydrate formation. This is how CO2 is ultimately built into sugar rather than wasted, stored, or broken down in this part of photosynthesis.