The processes that break down complex molecules into simpler ones are called catabolic reactions.

Here's why:

* Catabolism is the breakdown of complex molecules into simpler ones, often releasing energy in the process.

* Anabolism is the building up of complex molecules from simpler ones, requiring energy.

Together, catabolism and anabolism make up metabolism, the sum of all chemical processes in a living organism.

Examples of catabolic reactions:

* Digestion: Breaking down food into smaller molecules like glucose, amino acids, and fatty acids.

* Cellular respiration: Breaking down glucose to release energy in the form of ATP.

* Breakdown of proteins: Proteins are broken down into amino acids.

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