Question

1. Cellular ATP hydrolysis does not always release exactly the same amount of energy. Provide a thermodynamic explanation for this observation. (hint, do your reading in Cell Bio by the numbers!)

In the conditions of a muscle cell recovering from severe exercise, would you expect the hydrolysis of one mole of ATP molecule to produce MORE or LESS energy? Circle one and explain your reasoning.

Answer 1

A. ∆G for the hydrolysis of one mole of ATP into ADP and Pi​ is −7.3 kcal/mol) under standard conditions (1 M concentration of all molecules, 25°C and pH = 7.0). That’s not bad, but things get more impressive under non-standard conditions: ∆G for the hydrolysis of one mole of ATP in a living cell is almost double the value at standard conditions, around −14 kcal/mol (−57kJ/mol).

B. More energy, because all muscle cells contain a high-energy compound called creatine phosphate which is broken down to make more ATP quickly. Creatine phosphate can supply the energy needs of a working muscle at a very high rate, but only for about 8–10 seconds.