Final answer:
ATP is vital for numerous cellular functions and is continuously synthesized due to its rapid consumption in biological processes. Excess ATP, along with glucose, can be stored as glycogen in the liver and muscles, allowing for an energy reserve that can be mobilized when needed.
Step-by-step explanation:
Adenosine triphosphate (ATP) is the fundamental energy currency of the cell, required for a range of cellular functions, including building organic molecules, enabling muscle contractions, and facilitating electrical signal transmission in the nervous system. It is not that humans synthesize ATP for fun or because it is required for heating the body, nor is excess ATP excreted.
The synthesis of ATP is a continuous process because existing ATP molecules are rapidly consumed by various biological processes, and their energy is quickly expended. Thus, a copious amount of ATP is perpetually required to sustain necessary functions. In periods when ATP and glucose are in excess, the liver can convert and store them as glycogen, which provides a reserve of energy that is available during intense exercise or when the blood sugar level drops.