The term catabolism covers all metabolic processes of the body in the course of which the complex and sometimes high-molecular proteins, carbohydrates (polysaccharides), and fats are broken down into their simpler building blocks, usually with the generation of energy. The individual building blocks are then available for the synthesis of new required substances or are further broken down and excreted.
What is catabolism?
Catabolism is the term used to describe all metabolic processes in the body during which proteins, carbohydrates, and fats are broken down into their simpler building blocks. Metabolic processes that involve the breakdown of higher molecular weight substances into lower molecular weight substances are subsumed under the term catabolism. These are usually multistage to multistep processes that are mostly exothermic. The exothermic processes are biocatalytically controlled by enzymes, vitamins and hormones in order to be able to use the released energy for the body in the form of heat or chemical energy for the endothermic build-up of substances and to protect the immediate reaction environment from burns. The body depends on energy production through catabolic metabolic processes because, unlike green plants, it cannot perform photosynthesis, on whose energy production and conversion into storable chemical energy all aerobic life is based. Carbohydrates are broken down by the use of enzymes such as amylases and saccharases to simple sugars to glucose. Glucose, in turn, can be metabolized to build new substances or further metabolized for energy to carbon dioxide and water and excreted. Similar degradation processes include protein and fat catabolism. High-molecular-weight proteins are degraded into low-molecular-weight peptides to yield single amino acids, which are further metabolized or used to build new proteins. Fats are degraded to fatty acids and subsequently metabolized in a manner similar to carbohydrates.
Function and task
Catabolism or catabolic metabolic processes perform four different main tasks and functions. The first main task is for energy production in the form of usable heat or in the form of chemical energy for subsequent heat utilization or for the endothermic buildup of new needed substances. In case of need, for example, the starch formed and stored via anabolic processes is converted back into glucose via catabolic turnover and made available to the cell. Another task is to make the degradation products of proteins, carbohydrates and fats, which are needed for anabolism (building metabolism), available for building new substances. This is a kind of recycling process, also known as the salvage pathway. A major advantage is that it is energetically less costly to assemble proteins, enzymes and hormones from recycled larger pieces than it is to synthesize them from scratch from the required molecules, with appropriate energy input. The third task, while also very important, could also be considered a useful side effect. The importance of many complex substances such as enzymes, hormones and vitamins lies in their bioactivity and catalytic action. If a particular enzyme or hormone has served its purpose, it must be rendered inactive or replaced by its counterpart. This is where catabolism plays a significant role. As soon as a hormone, enzyme or vitamin is metabolized, i.e. catabolized, its bioactivity is abruptly interrupted. A similar process can occur with certain toxins, which lose their toxic effect through catabolism and can be further metabolized as degradation products of the toxin to be excreted as residues, e.g. via the kidneys. In the fourth task of catabolism, the body is able to use metabolic processes to break down the body’s own proteins, fats and carbohydrates for the purpose of energy production or to use them to obtain certain amino acids or other urgently needed compounds. This enables the body to survive several days without food intake and to break down body tissue as needed and build it up elsewhere. To prevent conflicts within a cell, catabolic and anabolic metabolic processes do not run simultaneously, but always temporally separated from each other.Enzymes of catabolic processes inhibit enzymes of anabolic processes and vice versa. Certain phosphatases can reverse the direction of metabolism into anabolic or catabolic, respectively.
Diseases and disorders
Catabolism encompasses a variety of enzymatically catalytic, biochemical metabolic processes that are always interrelated with their counterpart, anabolism. Complaints and problems therefore arise not so much from an overall dysfunction, but as a rule from the absence of certain enzymes or from their biochemical ineffectiveness due to a genetic defect leading to faulty synthesis of the enzyme. Basically, however, there are situations that lead to mainly catabolic metabolism, since body substances have to be broken down more frequently in order to prevent poisoning or flooding with substances that are harmful to the body. Such situations arise, for example, in muscle paralysis, myocardial infarction, stroke and other types of atrophy. Disorders of catabolic metabolism can be present in carbohydrate metabolism, protein metabolism, and fat metabolism, and can lead to mild to severe symptoms and diseases. The metabolic disease diabetes is caused by a lack of insulin or resistance to the effectiveness of insulin and can lead to serious acute conditions. As a result of malnutrition, which, for example, contains too little protein and does not provide an adequate supply of essential amino acids, the body increasingly switches to catabolic metabolism, mobilizes all available energy reserves and gradually breaks down body substance in order to be able to provide the body with energy. In order to use as few of the body’s own reserves as possible, the body simultaneously switches to a kind of energy-saving mode. Brain performance slows down and physical performance becomes much more difficult.
