(6.1) The pk of the following acid-base reactions, HA A + H+, is approximately 7. HPO4 HPO + H+ HADP ADP + H+ HATP3 ATP+H+ On the assumption that, at pH 7, we may ignore other charged species of these compounds, show that the average charge of P, ADP, and ATP is -1.5, -2.5, and -3.5, respectively, by expressing the probability, A, of the deprotonated state, A-, in terms of pH and pKa, and the average charge in terms of the probabilities of protonated and unprotonated state, A and HA. 5