Tasks for detoxification
The liver is one of the most important tissues for biotransformation. This is the transformation of substances that cannot be excreted into excretable substances. This is particularly important for substances that are harmful to the body, so that they do not accumulate in the body.
Many such substances are converted in the liver. These include alcohol, medicines, harmful substances and toxic metabolic waste products. They reach the liver via the blood vessels and are converted or excreted there.
The conversion reaction involves two steps. In the first step, a functional group, for example -OH or -SH, is attached to the substance (conversion reaction) and in the second step the molecules are attached to water-soluble substances via the functional group (conjugation reaction). Important enzymes for these reactions are the cytochrome 450 oxygenases.
They are responsible for a phase 1 reaction and are only slightly substrate specific. This means that they can convert many different substances. Once the substances have been converted into water-soluble substances in the liver, they can be released into the blood and excreted via the kidneys (for example, ammonia to urea).
Other substances cannot be released into the blood, but are excreted through the bile. These include the blood pigment haemoglobin, for example. It is broken down in the liver to bilirubin.
This is then conjugated (coupled) and transported in the bile bound to bile salts to be excreted through the intestines. This also applies to many drugs. Alcohol is also broken down in the liver.
However, there are specific enzymes for this purpose. In the first step, alcohol is converted by alcohol dehydrogenase into a harmful intermediate product, aldehyde. This must now be converted into acetic acid by another enzyme, aldehyde dehydrogenase.
People who do not have enough of this second enzyme are more likely to suffer from nausea and severe headaches. The liver is therefore the central organ for the detoxification of various substances through biotransformation. If the reactions of biotransformation no longer work or if the liver is no longer functional, serious damage to the body can occur due to accumulation of these harmful substances (drugs, alcohol, waste products).
Resorption phase
In the resorption phase (directly after food intake), the nutrients are absorbed from the intestine into the liver, where they are converted into storage products and energy suppliers. The energy suppliers are then transported to the various organs, where they are available for the metabolic processes of the individual organs. As soon as all organs are supplied, the excess glucose is converted into glycogen and stored in the liver, or, in the case of high quantities, converted into fat.
The fatty acids are converted into triacylglycerides (fats) and stored in the fatty tissue and the amino acids are converted into proteins and enzymes and made available for the corresponding functions. Some of them can also be stored at various end organs in storage vesicles (small roundish vesicles) (e.g. insulin, thyroid hormones). In this way, the liver builds up a supply when there is an abundance, which then serves to supply all vital organs and functions during periods of hunger. It is only through these storage possibilities that we can do intense sport and sometimes not eat for hours without our body having to restrict its functions.
