Catabolism is the series of chemical reactions that breakdown larger molecules. Energy is released this way, some of it can be utilized for anabolism. Products of catabolism can be reassembled by anabolic processes into new anabolic molecules. Enzymes function as organic catalysts. A catalyst is a chemical involved in, but not changed by, a chemical reaction.
Many enzymes function by lowering the activation energy of reactions.
By bringing the reactants closer together, chemical bonds may be weakened and reactions will proceed faster than without the catalyst. Image from W.H. Freeman and Sinauer Associates, used by permission. Carbonic anhydrase speeds up the transfer of carbon dioxide from cells to the blood. There are over 2000 known enzymes, each of which is involved with one specific chemical reaction. Enzymes are substrate specific.