Glycolysis and Gibbs Free Energy

[Sylvia Zhang 2L]

I'm taking LS 7A right now, and a couple weeks ago in class we mentioned that even though some steps of glycolysis were technically nonspontaneous under standard conditions, in cellular conditions, they become spontaneous. Why does this occur?

[Joah Lee]

Delta G and standard delta G are two different things. Standard delta G is under certain conditions (1 bar, 298K, 1 mole of gas, 1M solute). However, changing temperature and the concentrations of the products and reactants can influence the real delta G of a reaction. Glycolysis occurs at a certain temperature or concentration that could delta G positive or negative depending on the conditions the cell is in.

delta G = standard delta G + RT ln Q

[Rakshaa Venkatraman 2F]

Conditions like concentrations of reactants and products can affect delta G at nonstandard conditions and make the reaction spontaneous - this is likely what happens. This relates to the equation ΔG = ΔG° + RT ln Q. Another way a non-spontaneous reaction could be made spontaneous is by coupling the non-spontaneous reaction with a spontaneous one.