Question

The amount of energy given by one ATP molecule is
A. 67 Kcal
B. 6.7 Kcal
C. 7.6 Kcal
D. 76 Kcal

Answer 1

Hint: Adenosine triphosphate is an organic compound that provides energy to drive many processes in living cells. ATP captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular processes.

Complete answer: The calculated $∆G$ for the hydrolysis of one mole of ATP into ADP and Pi is $−7.3 kcal/mole$ (approximately $8 kcal/mole$). Since this calculation is true under standard conditions, it would be expected that a different value exists under cellular conditions. In fact, the $∆G$ for the hydrolysis of one mole of ATP in a living cell is almost double the value at standard conditions: $14 kcal/mol (−57 kJ/mol)$.
So, the answer is C, i.e., 7.6 Kcal
Additional information:
ATP consists of adenine attached by the 9-nitrogen atom to the 1′ carbon atom of a sugar (ribose), which in turn is attached at the 5' carbon atom of the sugar to a triphosphate group. In its many reactions related to metabolism, the adenine and sugar groups remain unchanged, but the triphosphate is converted to di- and monophosphate, giving respectively the derivatives ADP and AMP. The three phosphoryl groups are referred to as the alpha (α), beta (β), and, for the terminal phosphate, gamma (γ).

Note: ATP is also a precursor to DNA and RNA, and is used as a coenzyme. ATP is classified as a nucleoside triphosphate, which indicates that it consists of three components: a nitrogenous base (adenine), the sugar ribose, and the triphosphate.