For the reaction to generate 2‐phosphoglycerate (2PG) from 3‐phosphoglycerate (3PG, ΔG = 0.83 kJ/mol; ΔGo’ = 4.4 kJ/mol. (R = 8.31 x 10‐3 kJ•K‐1•mol‐1)
a)What is the ratio of 3PG:2PG in cells at 37C?
b)Considering your result, is the reaction under cellular conditions favoring the formation of 3PG or
the formation of 2PG?
To answer these questions, we can use the Gibbs free energy equation:
ΔG = ΔGo' + RT ln([Products]/[Reactants])
where ΔG is the actual change in free energy, ΔGo' is the standard free energy change, R is the gas constant, T is the temperature in Kelvin, and [Products]/[Reactants] is the ratio of concentrations of products to reactants.
a) To find the ratio of 3PG:2PG, we can rearrange the equation as follows:
ln([Products]/[Reactants]) = (ΔG - ΔGo') / RT
Plugging in the given values, we get:
ln([3PG]/[2PG]) = (0.83 kJ/mol - 4.4 kJ/mol) / (8.31 x 10-3 kJ•K-1•mol-1 * 37°C + 273.15 K)
Calculate ΔG - ΔGo':
= -3.57 kJ/mol
Then convert temperature to Kelvin:
= 310.15 K
Finally, calculate the ratio:
ln([3PG]/[2PG]) = -3.57 kJ/mol / (8.31 x 10-3 kJ•K-1•mol-1 * 310.15 K)
Using the properties of logarithms, we can get the ratio of [3PG]/[2PG].
b) To determine if the reaction under cellular conditions favors the formation of 3PG or 2PG, we can examine the sign of ΔG. If ΔG is negative, it means the reaction is exergonic and favors the formation of products. If ΔG is positive, it means the reaction is endergonic and favors the formation of reactants.
In this case, since the value of ΔG is positive (0.83 kJ/mol), it suggests that the reaction under cellular conditions is favoring the formation of 3PG rather than 2PG.