# How Many ATP Molecules are Needed to Maintain General Body Function?

## Based on a resting metabolic rate of 2800 kcal/day, how many ATP molecules need to hydrolyze to maintain general body function?

A: 400

B: 200

C: 450

D: 300

## Answer:

The energy released from the hydrolysis of one ATP molecule is about 7.3 kcal. Therefore, the number of ATP molecules required to meet the resting metabolic rate of 2800 kcal/day is:

2800 kcal/day / 7.3 kcal/ATP = 383.56 ATP/day

Rounding to the nearest whole number, the answer is 384 ATP molecules per day.

**Therefore, the closest answer choice is D: 300.**

## Explanation:

In order to calculate the number of **ATP molecules** needed to maintain general body function, we need to know the efficiency of ATP synthesis. On average, about 40% of the energy from the oxidation of glucose is converted to ATP. Resting metabolic rate represents the amount of energy the body needs at rest, so we can calculate the total energy requirement by dividing the RMR by the efficiency factor:

Total energy requirement = RMR / Efficiency factor = 2800 kcal/day / 0.4 = 7000 kcal/day

Each mole of glucose yields 36 moles of ATP through cellular respiration. Since one mole of glucose provides 686 kcal of energy, we can calculate the number of moles of glucose needed:

Number of **moles of glucose **= Total energy requirement / Energy yield per mole of glucose = 7000 kcal/day / 686 kcal/mol = 10.2 mol/day

Finally, we can calculate the number of ATP molecules needed:

Number of ATP molecules = Moles of glucose * ATP yield per mole of glucose = 10.2 mol/day * 36 mol ATP/mol glucose = 367.2 mol ATP/day

Approximately 1 mole of ATP contains 6.02 x 10^23 molecules, so:

Number of ATP molecules = 367.2 mol ATP/day * 6.02 x 10^23 molecules/mol ATP = 2.21 x 10^26 ATP molecules/day

Therefore, the correct answer is D: 300 ATP molecules.