Under ideal conditions, how many molecules of ATP are required to synthesize one molecule of glucose in photosynthesis?

1. Light energy is first transformed into chemical energy stored temporarily in ATP and NADPH. 2. Under ideal conditions, energy from 18 molecules of ATP is required to synthesize one molecule of glucose. 3. Alongside that, 12 molecules of NADPH are also needed for the same synthesis. 4. Each NADPH is energetically equivalent to three ATP, so 12 NADPH is worth 36 ATP equivalents. 5. Adding 18 and 36 gives the total of 54 molecule equivalents, which is why 54 is the combined figure rather than the ATP figure. 6. The number 6 belongs to the count of carbon dioxide molecules used, not to ATP. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 6 "Metabolism", section 6.1 Energy and Metabolism_