This lecture covers the calculation of reaction quotient in the context of an enzyme reaction, using the example of the L-glutamate pyruvate transphérase enzyme converting L-glutamate to alpha-ketoglutarate and L-alanine. By determining the reaction direction based on the calculated quotient, the equilibrium concentrations of the involved species are found through a quadratic equation solution, resulting in specific concentration values for alpha-ketoglutarate, L-alanine, glutamates, and pyruvates.