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Catabolic reactions give out energy. They are exergonic. In a catabolic reaction large molecules are broken down into smaller ones. For example, the reverse of the condensation reactions described above, i.e. hydrolysis reactions, are catabolic.
Catabolic pathways are metabolic pathways that release energy, or ATP, by breaking down complex molecules into simpler ones (cellular respiration). Anabolic pathways are metabolic pathways that consume energy, ATP, to build complicated molecules from simpler ones (photosynthesis). Metabolic reactions are coupled so that the energy released from a catabolic reaction can be used to drive an anabolic one.