Which nutrients are crucial for energy metabolism?

The correct choice highlights the significance of both carbohydrates and vitamins in the context of energy metabolism. Carbohydrates are particularly essential as they serve as the body's primary source of energy. When consumed, carbohydrates are broken down into glucose, which is utilized by cells for fuel. This process is vital for sustaining bodily functions and physical activities.

Vitamins, while not a direct source of energy, play crucial roles as coenzymes in metabolic processes. Certain vitamins, such as B vitamins, aid in converting carbohydrates, fats, and proteins into usable energy. They support various biochemical reactions that are integral to energy production, making them important contributors to the metabolism of energy.

In contrast, while proteins have a role in providing energy, they primarily serve as building blocks for growth and repair. Their conversion into energy is not the body's preferred pathway unless carbohydrates and fats are insufficient. Thus, the combined functions of carbohydrates as energy sources and vitamins as essential facilitators of metabolic reactions underscore why both nutrients are critically important for energy metabolism.