Cholesterol classification

 

Cholesterol  classification

Cholesterol is polycyclic alcohol. Traditionally it is counted as a steroid belonging to the sterols' group (sterols) to the lipids. However, contrary to popular confusion, it is not fat. The steroids belong to the group of isoprenoids, which, unlike the fats, are not esters of fatty acids and alcohol but can have hydrophilic poles as diverse patterns in their basic hydrophobic structure.  Globalmarketingbusiness

 

Like many substances, cholesterol is sensitive to oxidants. Autoxidation processes can lead to many reaction products. To date, more than eighty such substances are known, which often have considerable physiological effects. The oxidation products are isolated and purified by chromatographic methods. Your secure identification takes place at z. B. by spectroscopic or spectrometric techniques such as mass spectrometry. A comprehensive description of these cholesterol oxidation products is given in Leland L. Smith's work: Cholesterol Autoxidation. Nanobiztech

Physiology

Cholesterol is a zoosterol that is essential for humans and animals. In humans, cholesterol is mostly (90%) produced ( synthesized ) in the body, in adults in an amount of 1 to 2 g per day, and only a small part of it can be ingested with food. The cholesterol absorption is on average 0.1 to 0.3 g per day and maybe at most 0.5 g to be increased per day. Techcrunchblog

 

All animals synthesize cholesterol. Starting from "activated acetic acid," acetyl-CoA, isopentenyl diphosphate is produced in four steps via mevalonic acid. Another three reaction steps lead to squalene. After the ring closure to lanosterol, around a dozen enzymatic reactions follow, running in parallel until cholesterol is finally formed. This last section is not known in full, but the enzymes involved have been identified. Divinebeautytips

 

Cholesterol is excreted in the liver by being secreted into the intestines in the form of bile acids via the biliary tract (around 500 mg per day). Bile acids are necessary to absorb water-insoluble food components, including cholesterol. Cholesterol is emulsified by bile acids and interested in the small intestine. Since around 90% of the bile acids are reabsorbed, cholesterol's excretion is correspondingly ineffective. Through drugs like colestyramine, which binds bile acids and makes their re-absorption more difficult, cholesterol excretion can be increased. However, the lowering of the cholesterol level is compensated for by an increase in the density of LDL receptors on liver cells and the increased absorption of cholesterol from the blood into the liver, partly also by increased new synthesis.

 

Biosynthesis

The biosynthesis of cholesterol, which was elucidated in particular by Konrad Bloch's work, Feodor Lynen, George Joseph Popják, and John W. Cornforth, starts the end products of the mevalonate biosynthetic pathway, from dimethylallyl pyrophosphate and isopentenyl pyrophosphate, and requires 13 further reactions. In humans, the liver and the intestinal lining are the main cholesterol synthesis sites.

 

Regulation

The balance between required, self-produced, and cholesterol ingested through food is maintained through various mechanisms. The inhibition of HMG-CoA reductase, the most critical enzyme in cholesterol biosynthesis, by cholesterol (HMG-CoA reductase is even more strongly inhibited by lanosterol, a precursor of cholesterol) can be considered necessary. This metabolic pathway (cholesterol synthesis) inhibits "their" enzyme; this is a typical example of negative feedback. Also, HMG-CoA reductase's half-life is significantly shortened when the lanosterol level is increased. It then increasingly binds to the proteins Insig-1 and Insig-2binds, leading to their breakdown in the proteasome.  There are many other, less direct regulatory mechanisms that operate at the transcriptional level. The proteins SCAP, Insig-1, and Insig-2, are essential here. In the presence of cholesterol, for which they have a binding site, they regulate the activity of a large number of genes via the proteolytic activation of SREBPs. Also, insulin plays a role here, as it u. A. increases the transcription of SREBP1c. Marketingmediaweb

 

HMG-CoA reductase, the key enzyme in cholesterol biosynthesis, can be precisely and effectively inhibited by various substances (for example, statins, which, as HMG-CoA reductase inhibitors, represent a particular class of drugs). Uptake into the cell is activated via the LDL receptor.

 

The cholesterol level depends primarily on the body's production and only secondarily on food intake. There are also a large number of genetic hypercholesterolemia. The cholesterol level can also be increased due to other diseases (for example, due to hypothyroidism, renal insufficiency, or metabolic syndrome ).