Twelve NADPH molecules are used to build one glucose. Since each is worth three ATP, what is the total molecule equivalent cost of that glucose?

1. Building one glucose from six carbon dioxide needs 18 molecules of ATP and 12 molecules of NADPH. 2. Each NADPH is energetically equivalent to three molecules of ATP. 3. So 12 NADPH multiplied by 3 gives 36 ATP equivalents. 4. Adding the 18 ATP gives 18 plus 36, which is 54 molecule equivalents in total. 5. Answering 36 counts only the NADPH contribution and forgets the ATP itself. 6. Answering 30 or 48 comes from mis-multiplying the NADPH, since only a factor of three fits the stated equivalence. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 6 "Metabolism", section 6.1 Energy and Metabolism_