Final answer:
The principal carbohydrate used in the body is glucose, which serves as a critical energy source and can be converted into ATP, stored as glycogen, or transformed into fat.
Step-by-step explanation:
The principal form of carbohydrate used in the body is glucose. This simple sugar is a critical source of energy for the body, with all body cells capable of utilizing glucose for fuel. It is involved in energy production by being converted into adenosine triphosphate (ATP) through oxidation-reduction reactions. Glucose is not only a direct fuel source but also serves as the building block for the storage form of carbohydrates, namely glycogen. When not needed immediately for energy, glucose can be stored as glycogen in the liver and skeletal muscles or, alternatively, converted into fat for long-term energy storage in adipose cells.