In plants, it can be assumed that NADPH like NADH is energetically equivalent to 2.5 ATP. Calculate the number of ATP and ATP equivalents that are needed to synthesize one molecule 0f glucose-6-phosphate from CO2 and photosynthetically produced ATP and NADPH.
To calculate the number of ATP and ATP equivalents needed to synthesize one molecule of glucose-6-phosphate, we first need to understand the steps involved in the synthesis process.
1. First, let's identify the major steps involved in the synthesis of glucose-6-phosphate:
a) Fixation of CO2 in the Calvin cycle
b) Reduction of PGA (3-phosphoglycerate) to G3P (glyceraldehyde-3-phosphate)
c) Regeneration of RuBP (ribulose 1,5-bisphosphate) in the Calvin cycle
d) Conversion of G3P to glucose-6-phosphate
2. Next, let's determine the number of ATP and NADPH required in each step:
a) Fixation of CO2: In this step, 3 molecules of ATP and 2 molecules of NADPH are consumed per 3 molecules of CO2 fixed.
b) Reduction of PGA to G3P: 3 molecules of ATP and 2 molecules of NADPH are consumed per 1 molecule of PGA reduced to G3P.
c) Regeneration of RuBP: 5 molecules of ATP are consumed per 3 molecules of CO2 fixed (this step occurs three times to regenerate 3 molecules of RuBP).
d) Conversion of G3P to glucose-6-phosphate: 1 molecule of ATP is consumed per 1 molecule of G3P converted to glucose-6-phosphate.
3. Now, let's calculate the total number of ATP and ATP equivalents required:
a) Fixation of CO2: (3 ATP + 2 NADPH) x (1 CO2) = 3 ATP + 2 NADPH equivalents
b) Reduction of PGA to G3P: (3 ATP + 2 NADPH) x (1/3 PGA) = 1 ATP + (2/3) NADPH equivalents
c) Regeneration of RuBP: 5 ATP x (1 CO2) = 5 ATP equivalents
d) Conversion of G3P to glucose-6-phosphate: 1 ATP x (1 G3P) = 1 ATP equivalent
4. Finally, let's sum up the ATP and ATP equivalents required in each step to get the total number:
Total = (3 ATP + 2 NADPH equivalents) + (1 ATP + (2/3) NADPH equivalents) + 5 ATP equivalents + 1 ATP equivalent
Therefore, the total number of ATP and ATP equivalents needed to synthesize one molecule of glucose-6-phosphate is equal to:
Total = 4 ATP + (8/3) NADPH equivalents
Please note that the conversion of NADPH to ATP equivalents depends on the specific energy transfer mechanisms and metabolic pathways within the plant.