Which set of reactions uses ATP and NADPH to synthesize sugars?

• A. Calvin cycle
• B. Chloroplast
• C. Chlorophyll
• D. Light dependent reactions

Answer: (A)

The set of reactions that uses ATP as energy and NADPH as reducing power to build sugars is the Calvin cycle. In this cycle, carbon dioxide is fixed into a sugar precursor through a series of steps that require ATP to drive transformations and NADPH to provide the high-energy electrons needed to reduce carbon compounds. The carbon skeleton is ultimately assembled into glyceraldehyde-3-phosphate, which can be used to synthesize glucose and other carbohydrates. This process occurs in the stroma of the chloroplast, using energy and reducing power supplied by the light-dependent reactions. The other options describe parts of the photosynthetic apparatus or stages that generate ATP and NADPH rather than using them to make sugars.