Nitrogen balance
In medicine, the nitrogen balance is a laboratory value that can be used to assess the protein metabolism quite meaningfully . It indicates the relationship between nitrogen uptake and release in the organism.
Basics
Proteins essentially consist of many amino acids strung together . Each of these amino acids contains at least one nitrogen atom. If proteins are broken down from the muscles, for example, individual amino acids are created. When they are metabolized, nitrogen is produced, which has to be excreted via the kidneys . To do this, it is first converted to urea in the liver . The nitrogen balance is the difference between the amount of nitrogen absorbed and excreted.
If more proteins are broken down by the body than built up in the balance, especially in the muscles , which is the case, for example, in times of hunger (catabolic metabolism), the nitrogen balance is negative . The body loses so nitrogen compounds by the protein and amino acids degradation.
If, on the other hand, a person takes in 10 grams of nitrogen, for example, but only gives off 5 grams, there is a positive nitrogen balance. This is the case, for example, during growth or regeneration times for strength athletes. More nitrogen is absorbed than released, and thus more protein is built up than broken down.
This also shows whether the body is going through a metabolic crisis (e.g. due to long fasting or illness). Towards the end of the crisis, it swings back into the anabolic (anabolic) metabolism, in which proteins are built up again.
Protein catabolism is of particular importance to humans. He cannot build up glucose from stored fat (the other way around), but he always needs glucose for the high-energy fat breakdown, otherwise the energy balance deteriorates. The brain and red blood cells also depend on glucose. In a hypoglycemia may even lead to acidification of the blood. However, liver cells are able to carry out gluconeogenesis , i.e. to produce glucose. In particular, the protein components, the amino acids, are converted into glucose.
In detail, the liver cells split off the amino (nitrogen) ends of the simple amino acids . The remaining carbon structure then gives rise to intermediates of the citric acid cycle and "feeders" of gluconeogenesis and fatty acid synthesis. The above-mentioned nitrogen is produced in the form of ammonia, which is packed in urea and excreted via the kidneys.
swell
- Nutritional medicine: According to the nutritional medicine curriculum of the German Medical Association; ISBN 978-3-13-100293-8 .
- Hermann Hager, Hubert Schneemann, Gisela Wurm; Pharmaceutical Practice Manual; ISBN 978-3-540-58958-7 .
- Werner Müller-Esterl: Biochemistry: An Introduction.
See also
Other meanings
The term nitrogen balance also means the relationship between the build- up and breakdown of nitrogen compounds in the nitrogen cycle in the atmosphere, in water, in soils and in biomass in general.