Two different proteins X and Y are dissolved in aqueous solution at 37 ∘C. The proteins bind in a 1:1 ratio to form XY. A solution that is initially 1.00 mM in each protein is allowed to reach equilibrium. At equilibrium, 0.23 mM of free X and 0.23 mM of free Y remain. What is Kc for the reaction?

Kc = 1.4556 * 104

Explanation:

Two different proteins X and Y will bind in a 1:1 ratio to form XY

X + Y ⇔ XY

This means that for 1 mole X consumed, there will be 1 mole of Y consumed and 1 mole of XY produced

Both proteins X and Y have initially 1mM ( = 0.001M)

if there is consumed x moles of protein X then there will also be consumed x moles of protein Y. As given the remaining concentration of both proteins X and Y is 0.23 mM ( = 0.23 * 10^-3 M).

This means also that here will be produced x of the protein XY

x = 10^-3 - 0.23*10-3 = 7.7 * 10^-4 M

Kc = [XY] / [X][Y]

Kc = 7.7 * 10^-4 / ((0.23 * 10^-3) * (0.23 * 10^-3))

Kc = 1.4556 * 104