The breakdown of large complex molecules into smaller simpler ones is called catabolism.

Here's why:

* Catabolism is one of the two main types of metabolic reactions. The other is anabolism, which builds complex molecules from simpler ones.

* Metabolic reactions are the chemical processes that occur within living organisms to maintain life.

* Catabolic reactions generally release energy, which can be used by the organism for other processes.

Examples of catabolic reactions:

* Digestion: Breaking down food molecules (carbohydrates, proteins, fats) into smaller units.

* Cellular respiration: Breaking down glucose (a sugar) to produce energy in the form of ATP.

* Breakdown of glycogen (stored energy) into glucose.

Let me know if you have any other questions!