Dissimilation represents one of the most central processes in the organism of any breathing creature. It ensures the maintenance and intact functioning of the entire metabolism, cardiovascular system, and central nervous system. However, this importance results in the presence of many serious consequences and symptoms of disease in the event of a disturbed process at the same time.
What is dissimilation?
Dissimilation takes place in the cells of the human body. The term “dissimilation” is derived from the Latin term ‘dissimilis’ (= dissimilar) or ‘dissimilatio’ (= making dissimilar). Dissimilation is based on the enzymatic breakdown of endogenous substances that are initially absorbed through food. These include fats and carbohydrates as well as glucose. Following their degradation, the excretion of the foreign substances now present occurs in the form of water and carbon (dioxide). Furthermore, during the entire dissimilation process, large amounts of energy are obtained, which the cells store and process in the form of the universal energy transmitter adenosine triphosphate (ATP). Per molecule of glucose, the number of ATP molecules obtained is 38. There is also a differentiation between oxidative energy gain (= reaction process with oxygen), also called aerobic respiration, and anaerobic respiration (= without the influence of oxygen). The latter is known in everyday language mainly as fermentation.
Function and task
Dissimilation takes place in the cells of the human body. It includes the four substeps of glycolysis, oxidative decarboxylation, citrate cycle, and the final respiratory chain, also known as end oxidation. Apart from glycolysis, which takes place in the cytoplasm, all other subprocesses take place in the mitochondria or at their inner membrane. Mitochondria are small cell organelles that are enclosed by a double membrane and thus isolated from the cell plasma. If a human ingests glucose via food, an energy application phase first begins in which a phosphate group attaches to the sixth carbon atom of the glucose molecule. This comes from a previous cleavage of a molecule of ATP into ADP (= adenosine diphosphate). After the same process has been repeated, the glucose with its six carbon atoms breaks down into two molecules with three carbon atoms each. The energy release phase then begins. The phosphates detach from the carbon atoms and combine with ADP to form ATP. Water molecules are split off and a high-energy reduction of the substance NAD to NADH+H+ takes place. The latter products are called “reduction equivalents” and serve to transfer and store electrons. This is followed by oxidative decarboxylation. Here, too, a comparable reduction takes place first; however, the original glucose molecule subsequently links with a coenzyme in order to be able to enter the citrate cycle. Fats first pass through the fatty acid cycle and are then introduced into the citrate cycle at a suitable point. Here, the molecule undergoes a series of different, new compounds and splitting off of atoms. All these processes contribute primarily to providing sufficient further electron carriers for final oxidation and to disposing of carbon dioxide, which is toxic to humans. At the inner mitochondrial membrane as well as in the gap between inner and outer membrane (= intermembrane space) the reduction equivalents arrive and oxidize. This causes electrons to pass through various protein complexes at the inner membrane and at the same time hydrogen protons are pumped into the intermembrane space. These combine with oxygen atoms and leave the cell as a water molecule. The respiratory chain represents, energetically, the most important part of the entire dissimilation. The formed forces and concentration differences between the inner and outer environments of the mitochondrion result in the formation of 34 molecules of ATP.
Diseases and disorders
For the generation of such a high number of ATP to occur, sufficient oxygen must be available. However, under anaerobic conditions, that is, during fermentation, this is lacking, so that end oxidation cannot occur. This in turn has the consequence that with the same energy input, only a ten percent energy production takes place, since ultimately only four of the actual 38 molecules of ATP can be produced.Such (lactic acid) fermentation occurs, for example, during sports or comparable physical exertion. This is noticeable by a painful burning of the muscles, since these overacidify due to the excess and not completely degraded products. A permanently disturbed energy production, caused for example by the lack of corresponding coenzymes, an insufficient oxygen supply from the outside or by the intake of water rich in harmful substances, can lead to cancer in the case of hardship. Such a disorder can be recognized at an early stage by the reduced body temperature of the affected person. After all, the release of heat goes hand in hand with the production of energy. But less drastic complaints can also be the result of a briefly reduced oxygen supply to the cells. For example, a deficiency in the cells of the brain leads to concentration problems and fatigue. At the same time, the deficiency in the heart, lungs and arteries can cause extreme fatigue and circulatory problems, even collapse. In addition, the entire immune system is weakened by the lack of oxygen in the cells, so that an increased susceptibility to all diseases must be assumed. Likewise, the central nervous system consists of dissimilation-operating cells, the neurons. Since these also do not work correctly when dissimilation is incomplete and may become over-acidic, the nervous system becomes overexcitable. This manifests itself in the form of nervousness, irritability, and even muscle tremors and muscle pain. Stress and overstimulation can also be the cause of disturbed dissimilation. To counteract a chronic disturbance of dissimilation in the entire organism, it is recommended to pay attention to a healthy, balanced diet as well as to sufficient exercise, ideally in the fresh air. It is also important to avoid unnecessary physical and mental stress.
