Final answer:
Glucose is the specific carbohydrate used as the main energy source by the human body. It comes from dietary sugars and the breakdown of complex carbohydrates, with excess stored as glycogen or fat.
Step-by-step explanation:
The specific carbohydrate that serves as the main fuel or energy source for the human body is glucose. This monosaccharide is a critical component in the energy supply for cells and is derived either directly from dietary sugars or from the breakdown of complex carbohydrates. When immediate energy needs are met, any excess glucose is converted into glycogen and stored in the liver and muscles, or it can be transformed into fat for long-term energy storage.
The body prioritizes carbohydrates as a source of energy, and despite not being technically necessary in the diet, carbohydrates are widely consumed because they are a cost-effective and readily available energy source. During the digestion process, carbohydrates are broken down into their simpler forms, like glucose, to provide energy for cellular function and activities.