Final answer:
The primary source of energy in mammals is glucose derived from carbohydrates. Cells extract energy from ATP rather than from the bonds of carbohydrates directly, as ATP is a readily available and immediately usable form of energy. Carbohydrates are metabolized more efficiently than fats or proteins because they can be easily converted to ATP.
Step-by-step explanation:
The primary source of energy in mammals is carbohydrates, mainly glucose. Glucose is converted from digestible carbohydrates through a series of catabolic chemical reactions. It is more efficient for cells to extract energy from ATP rather than from the bonds of carbohydrates directly because ATP is a readily available and immediately usable form of energy.
When glucose or other carbohydrates are broken down, ATP molecules are synthesized through the process of cellular respiration. This conversion of glucose to ATP occurs in the mitochondria of cells. ATP is then used as a source of energy for various cellular activities.
Fats and proteins are also sources of energy in mammals, but carbohydrates are metabolized more efficiently because they can be easily converted to ATP. Fats and proteins require more complex processes to be converted into ATP, making them less efficient sources of energy.