* Catabolic reactions break down complex molecules into simpler ones. Glycolysis breaks down glucose (a complex sugar) into two molecules of pyruvate (a simpler molecule).

* Catabolic reactions release energy. Glycolysis generates a net gain of 2 ATP molecules (energy currency of the cell).

In contrast, anabolic reactions build up complex molecules from simpler ones and require energy.

Let me know if you have any other questions!