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Synthesizes Cholesterol And Fat – How Cholesterol is Synthesized
Cholesterol is an organic fatty substance that belongs to the steroid family and is present in every cell of the human body. This waxy substance is extremely important for human existence because it serves as a precursor to synthesize many of the body’s compounds, such as steroids hormones, vitamin D, and bile acids.
The body has the capacity to produce cholesterol, this process is conducted in the liver to be more precise.
However, this is not the only source of cholesterol for the body, as it is also found in animal foods, like egg yolks, milk, cheese, and meat. In other words, the cholesterol of the blood can come from two sources, liver production or food.
This article is focused on how the body synthesizes cholesterol in the liver’s cells and provides it to all the body’s parts as needed. Interested to learn? Keep on reading to understand how this process works.
Synthesizes Cholesterol And Fat – Synthesis of Cholesterol
The liver is responsible for the major endogenous production of cholesterol. It is important to mention that the whole process of synthesizing cholesterol is very “expensive” for the organism in terms of energy cost, for this reason the organism has built in methods to avoid waste such as being capable of recycling cholesterol that was used to form bile acid, for example.
Another interesting fact is that cholesterol endogenous production is decreased when blood cholesterol is adequate, in other words, cholesterol production is based on a supply-demand basis.
As for the production itself, cholesterol synthesis is a multistep process that takes place in the cytoplasm and in the reticulum endoplasmatic. The two precursor of cholesterol productions are Acetyl CoA and Acetoacetyl CoA, these two substances come together and are converted into 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA). This substance can be posteriorly used for a couple of different pathways, but here we will focus only in the cholesterol pathway.
In the cytosol, HMG-CoA is reduced to mevalonate (melavonic acid) by an enzyme called HMG-CoA reductase, this enzyme is critical in the cholesterol pathway as this is the rate limiting step in cholesterol production.
Once melavonic acid is produced, it goes through a pathway called the mevalonate pathway where it produces a substance called Isopentenylpyrophosphate, this substance is subsequently converted into Squalene. Afterwards Squalene is processed through a few reaction steps, converting into Lanosterol.
Finally, Lanosterol is processed via many different reactions in order to be converted into Cholesterol. It is important to mention that this is a simplified pathway regarding cholesterol production, however, it should give you an idea about how this complicated process evolves.
Furthermore, it is worth noting that cholesterol synthesis yields a number of molecules that are necessary for other important biological pathways.
How Cholesterol is Transported
As you have read, cholesterol is produced in the endoplasmatic reticulum and posteriorly delivered by the secretory pathway to a variety of intracellular organelles, some of this cholesterol ends up in the cell membrane, in which cholesterol plays an important role, mainly in structure and permeability.
In order to get into the bloodstream, cholesterol needs the help of a spherical particle called lipoprotein. Such particles have two parts, the protein fraction and the lipid fraction, and they are classified according to the content of each fraction.
The two most common lipoproteins are low-density lipoprotein (LDL), which has a higher lipid content, and high-density lipoprotein (HDL), which has a lower lipid content.
As for the cholesterol that comes from food consumption, the first step is breaking it down into smaller molecules from all the fat that was consumed in order for it to be absorbed, this process is carried out by the lipase enzymes with the help of bile acids in the small intestine.
Once absorbed, enterocytes (small intestine cells) package cholesterol into chylomicrons, and then release it into the bloodstream. Such chylomicrons possess a great number of triglycerides, which are used by adipocyte tissue and muscle as the chylomicron passes by them.
The remaining chylomicrons travel to the liver and there the liver cells repackage them into a lipoprotein called VLDL (very low-density lipoprotein), this lipoprotein contains a mix of triglycerides and cholesterol. VLDL is posteriorly released into the bloodstream and again adipocyte tissue and muscle remove the triglycerides turning the VLDL into LDL.
Function of Cholesterol
When it comes to functionality, cholesterol plays a huge role in many areas. Here are some key areas where cholesterol is vital:
Chemical precursor: Cholesterol is the precursor of many biological pathways, for instance, it is needed to synthesize vitamin D, sex hormones such as progesterone, testosterone, and estrogen as well as helping in the production of important hormones like cortisol and aldosterone.
Production of bile acids: bile acids are vital for the digestion of dietary fats. This substance acts like a biological detergent facilitating the absorption of fat and fat-soluble vitamins.
The bile acid production takes place in the liver, once ready it is deposited in the gallbladder in order for it to become more concentrated, finally, it is released in the duodenum, a part of the small intestine, whenever fat is consumed.
Cell membrane: cholesterol is present in every cell membrane and it helps with permeability and also regulates membrane fluidity.
Synthesizes Cholesterol And Fat Conclusion
Cholesterol is an essential fat substance present in the body as it is crucial for many biological pathways, the body has the capacity to produce all the cholesterol needed from two precursors, these are Acetyl CoA and Acetoacetyl CoA.
As for the production, cholesterol is synthesized in the liver cells (hepatocytes) by a complex and multistep process, which yields several substances that are later used in other important biological pathways.
The whole cholesterol production process is extremely costly to the organism, it uses a large amount of energy, and for this reason, this process is only requested when cholesterol plasma level is low.
Another source of cholesterol for the body is the dietary intake, cholesterol can also be found in animal food sources. After absorption, dietary cholesterol travels through the bloodstream via lipoproteins, which are classified according to the amount of lipid that it carries. Thank you for reading this Synthesizes Cholesterol And Fat article.