Catabolism

Catabolism (from Greek katabole—downward throw, destruction), a term for designating the processes of substance breakdown in the organism in general, i.e., the processes of dissimilation (see), and in this sense opposed to anabolism (see). Thus, anabolism and Catabolism together cover the whole sum of substance transformations in the organism, its entire metabolism, which in its generality is designated by the term "metabolism." Some authors, however, understand Catabolism as the breakdown in the organism of external substances without their prior assimilation by cells, i.e., without their introduction into the composition of the complex chemical system of living matter. In this case, Catabolism is usually opposed to metabolism as the transformation of substances proceeding with the direct participation of the body's cellular elements. The concept of the catabolic (in the sense just indicated) course of substance breakdown in the organism became especially clear in Liebig's teaching on the "respiratory" function of food carbohydrates and fats, which according to this teaching serve only as fuel, oxidizing in the blood under the direct influence of inhaled O₂. After the works of Voit and especially Pfluger, which showed that the site of oxidative processes is the tissues, Liebig's teaching lost its significance, and at present there are no sufficient grounds for a dual understanding of the term "catabolism."