Question

Why are ATP and NADPH both necessary for carbon fixation?

a) ATP provides energy for the conversion of carbon dioxide into organic molecules.
b) NADPH provides reducing power needed to convert carbon dioxide into organic molecules.
c) ATP and NADPH are involved in the synthesis of glucose during carbon fixation.
d) Both ATP and NADPH are essential for the overall process of photosynthesis.

Answer 1

ATP provides energy and NADPH provides reducing power necessary for the Calvin cycle in photosynthesis, which converts CO₂ into glucose. Together, these molecules facilitate the carbon fixation process, investing a total equivalent of 54 ATP molecules to synthesize one glucose molecule.

Step-by-step explanation:

ATP and NADPH are both necessary for carbon fixation during the process of photosynthesis due to the different roles they play. ATP provides the energy necessary for the conversion of carbon dioxide into organic molecules while NADPH donates electrons (reducing power) needed to convert the inorganic carbon dioxide into organic molecules during the Calvin cycle, which is the light-independent set of reactions in photosynthesis. The energy and reducing power from these molecules are used to convert carbon dioxide and ribulose bisphosphate (RuBP) into glyceraldehyde 3-phosphate (G3P), which can then be used to form glucose and other carbohydrates.

Solar energy captured during the light-dependent reactions is temporarily stored in ATP and NADPH. This energy is later used to synthesize one glucose molecule from six molecules of CO₂, in a series of reactions that consume 18 molecules of ATP and 12 molecules of NADPH. This reflects a significant energy investment, representing a total of 54 molecule equivalents of ATP for the full synthesis of one glucose molecule.