If a small amount of atp labeled with radioactive phosphorus in the terminal position, [γ-32p]atp, is added to a yeast extract, about half of the 32p activity is found in pi within a few minutes, but the concentration of atp remains unchanged. explain. if the same experiment is carried out using atp labeled with 32p in the central position, [β-32p]atp, the 32p does not appear in pi within such a short time. why?