Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 8

Backward or Forward The interconversion of dihydroxyacetone phosphate (DHAP)and glyceraldehyde-3-phosphate (G3P)is a part of both the glycolytic pathway and the Calvin cycle for photosynthetic carbon fixation:
(1)
The value of G°' for this reaction is +1.8 kcal/mol at 25°C. In the glycolytic pathway, this reaction goes to the right, converting DHAP to G3P. In the Calvin cycle, this reaction proceeds to the left, converting G3P to DHAP.
(a)In which direction does the equilibrium lie What is the equilibrium constant at 25°C
(b)In which direction does this reaction tend to proceed under standard conditions What is G' for the reaction in that direction
(c)In the glycolytic pathway, this reaction is driven to the right because G3P is consumed by the next reaction in the sequence, thereby maintaining a low G3P concentration. What will G' be (at 25°C)if the concentration of G3P is maintained at 1% of the DHAP concentration (i.e., if [G3P]/[DHAP] = 0.01)
(d)In the Calvin cycle, this reaction proceeds to the left. How high must the [G3P]/[DHAP] ratio be to ensure that the reaction is exergonic by at least 3.0 kcal/mol (at 25°C)