Question

The cleavage of ATP (adenosine triphosphate) to ADP (adenosine diphosphate) and \(\mathrm{H}_{3} \mathrm{PO}_{4}\) may be written as follows: It is interesting to determine which bond (the \(\mathrm{P}-\mathrm{O}\) bond marked a or the \(\mathrm{O}-\mathrm{P}\) bond marked \(\mathbf{b}\) ) is cleaved by hydrolysis (reaction with water). (a) Outline an experiment (using radioactivity) that can be used to determine where the cleavage results. (b) Describe the results that would lead you to conclude that cleavage results at a. (c) Describe the results that would lead you to conclude that cleavage results at \(b\). Results show that the cleavage occurs at b.

Short answer

Short Answer: Based on the experimental results using radioactive 32P atoms, the cleavage primarily occurs at bond b.

Step-by-step solution

(a) Design an experiment using radioactivity

In this experiment, two different ATP molecules, one with a radioactive 32P (phosphorus) atom at position a and the other with a radioactive 32P atom at position b, will be prepared. Use separate enzymes to catalyze the hydrolysis reaction for each type of ATP molecule. After providing a sufficiently large number of such reactions, analyze the resulting products, ADP and \(\mathrm{H}_{3}\mathrm{PO}_{4}\) using a radioactive detector to check for the presence of radioactive isotopes.

(b) Results indicating cleavage at bond a

If cleavage occurs at bond a, radioactive \(\mathrm{H}_{3}\mathrm{PO}_{4}\) will be detected primarily in the reactions using ATP with a radioactive 32P atom at position a, while radioactive ADP will be found mainly in the reactions using ATP with a radioactive 32P atom at position b. This would suggest bond a is primarily cleaved during hydrolysis.

(c) Results indicating cleavage at bond b

Conversely, if cleavage occurs at bond b, radioactive \(\mathrm{H}_{3}\mathrm{PO}_{4}\) will be detected primarily in the reactions using ATP with a radioactive 32P atom at position b, while radioactive ADP will be found mainly in the reactions using ATP with a radioactive 32P atom at position a. These results would indicate that bond b is primarily cleaved during hydrolysis. As the results show that the cleavage occurs at bond b, the experiment would have detected radioactive \(\mathrm{H}_{3}\mathrm{PO}_{4}\) mainly in the reactions using ATP with a radioactive 32P atom at position b, and radioactive ADP mostly in the reactions using ATP with a radioactive 32P atom at position a.