Runners only have enough stored ATP in their muscle cells to run for about five seconds. Which answer correctly explains how the runner's body adjusts to the longer distance, for example, a marathon (42.1 km)?

Answer Options:

A: The runner's body will convert stored fat molecules into energy.

B: The runner's body will create the needed energy by breaking down proteins.

C: The runner's body will supply the needed energy by producing starch.

D: The runner's body will produce the energy by activating the Golgi apparatus.

A: The runner's body will convert stored fat molecules into energy.

Explanation:

When the body needs energy to power cells, it uses ATP. ATP is generated by cellular respiration, which involves the breakdown of (usually) sugars by aerobic respiration.

If you exercise for a longer period such as during long distance running, your body will use more fat and less glucose in an attempt to conserve the limited glucose stores in case exercise intensity increases and oxygen availability is is reduced.