What is the primary source of energy for the body's cells?

The primary source of energy for the body's cells is glucose. Glucose, a simple sugar, is a key player in cellular respiration, the metabolic process that cells use to convert nutrients into energy. When carbohydrates are consumed, they are broken down into glucose, which then enters the bloodstream and can be utilized by cells for energy production.

In addition to providing energy, glucose is critical for the functioning of the brain, which relies heavily on it as a fuel source. Although other macronutrients like fats and proteins can also provide energy, glucose is the preferred and most efficient source, particularly for high-intensity activities and in circumstances where a quick energy release is necessary.

Fatty acids can be utilized for energy as well, particularly by muscles during lower-intensity exercises, but they require a more complex process to convert into usable energy. Proteins primarily serve as building blocks for tissues and are not typically used for energy unless carbohydrates are scarce. Vitamins, on the other hand, do not serve as energy sources themselves but play supportive roles in various biochemical reactions that help the body utilize energy from macronutrients.