What is an example of catabolism?

Catabolism refers to the metabolic process that breaks down larger molecules into smaller units, often leading to the release of energy. When considering the choices, breaking down food into energy is a prime example of catabolism. During digestion, complex molecules such as carbohydrates, proteins, and fats are hydrolyzed into simpler forms like glucose, amino acids, and fatty acids. This breakdown process not only helps in obtaining energy but also provides the necessary substrates for various metabolic pathways in the body.

In contrast, the other options represent different metabolic processes. Building muscle through exercise primarily involves anabolic processes where small units, such as amino acids, are used to create larger muscle proteins. The synthesis of cholesterol is also an anabolic process, as it involves assembling smaller molecules into larger, more complex structures. Absorbing vitamins from the diet, while essential for metabolism, refers to the uptake of nutrients rather than their breakdown. Thus, the correct identification of breaking down food into energy encapsulates the essence of catabolism effectively.