Which of the following describes catabolism?

Catabolism refers to the metabolic process that involves breaking down larger molecules into smaller units, often resulting in the release of energy. This process is essential for various functions in the body, including the maintenance of energy balance, the recycling of cellular components, and providing the building blocks for other biological molecules.

During catabolic reactions, complex substances such as carbohydrates, fats, and proteins are broken down into simpler forms. This breakdown is crucial not only for energy production but also for the removal of waste products from the body. By generating energy in the form of ATP, catabolism supports various physiological functions, such as muscle contraction, nerve impulse transmission, and maintaining body temperature.

In contrast, the other options describe processes that do not align with the definition of catabolism. For instance, building molecules is characteristic of anabolism, while creating new substrates for energy and stimulating muscle growth pertain to processes that involve energy utilization and biosynthesis rather than breakdown. Thus, the correct answer is directly aligned with the fundamental concept of catabolism as the breakdown of larger molecules into smaller, more manageable units.