Final answer:
Catabolism is the metabolic phase where complex substances are broken down into simpler molecules, releasing energy necessary for biological functions. It balances with anabolism, the phase of metabolism that builds complex molecules from simpler ones using cellular energy.
Step-by-step explanation:
In the phase of metabolism called catabolism, complex substances are broken down into simpler substances and converted into energy. This essential process releases energy as large, complex molecules found in food such as carbohydrates, fats, and proteins are degraded. Specifically, carbohydrates are broken down into simple sugars, fats into fatty acids and glycerol, and proteins into amino acids. This breakdown occurs through metabolic pathways, where catabolic reactions release the molecular energy stored in the bonds of these complex molecules.
Catabolism can be regarded as occurring in stages, including digestion in the mouth, stomach, and small intestine, where food molecules are hydrolyzed into monomer units. This catabolic phase balances with anabolism, the opposite metabolic phase where energy is used to synthesize larger molecules from smaller ones, sustaining the cell's energy balance.