What is the primary energy source for cellular functions?

The primary energy source for cellular functions is Adenosine Triphosphate (ATP). ATP serves as the energy currency of the cell, facilitating various biochemical reactions necessary for life. It is produced during cellular respiration and is used immediately for energy transfer processes, allowing cells to perform essential functions such as muscle contraction, nerve impulse transmission, and biosynthesis.

While glucose and glycogen are important for energy production, as glucose can be metabolized to generate ATP and glycogen serves as a stored form of glucose, neither directly fulfills the role of energy currency in the way ATP does. Protein, on the other hand, serves primarily as a building block for tissues and is not the primary source of energy for cellular functions. Instead, in a state of energy deficit, the body may break down proteins for energy, but this is not its primary function or source under normal conditions. By focusing on ATP, we emphasize its role as the immediate and essential energy molecule that powers cellular activities.