Question

In systemic tissue fluids, the enzyme carbonic anhydrase catalyzes the reaction CO2 + H2O → H2CO3 (which then can dissociate into H+ and HCO3-). In fact, CO2 released from cells is converted to HCO3- ions and travels in that form in the bloodstream. HCO3- is reconverted to CO2 + H2O in the pulmonary capillaries by the same enzyme, and there the CO2 is exhaled. How is it possible for the same enzyme to catalyze reverse reactions?

A. there must be two forms of carbonic anhydrase. One form catalyzes the forward reaction CO2 + H2O → H2CO3 and the other catalyzes the reverse reaction H2CO3 → CO2 + H2O
B. the direction of a reversible reaction is influenced by the concentrations of reactants and products. In pulmonary circulation, the low CO2 concentration favors the formation of CO2 and H2O
C. the lungs contain an allosteric inhibitor that prevents the formation of carbonic acid

Answer 1

B. the direction of a reversible reaction is influenced by the concentrations of reactants and products. In pulmonary circulation, the low CO2 concentration favors the formation of CO2 and H2O