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?