Lipoproteins are known as a set of macromolecular elements, which are made up of both lipids and proteins, which are responsible for the transfer of large amounts of fat throughout the body. Regarding their structure, they are wrapped in a polar cortex, which is composed of phospholipids, apoproteins and free cholesterol, within said cortex the nucleus of this macromolecule is located, consisting of triglycerides and esterified cholesterol. Lipoproteins are characterized by being water soluble and having a spherical shape. Some examples of lipoproteins are antigens, enzymes, and certain toxins.
The main function of lipoproteins is the transport of fat through the bloodstream to the different tissues of the body, as well as in the opposite direction, that is, from the tissues to the liver. It should be noted that lipids cannot circulate in the bloodstream due to their hydrophobic characteristics, for this reason it is necessary for these molecules to fuse with proteins in the blood. Proteins can be classified in order from largest to smallest by size and are as follows; Chylomicrons are located first, VLDLs are next, LDLs are third, and HDLs last.
This means that chylomicrons are the molecules with the largest size, however in terms of density they are the lowest level, while the densest but smallest are HDL. This level of density is measured according to the percentage of proteins that compose it, which means that if they have a high protein content and a lower amount of fat, the density will be much higher.
Each of the lipoproteins fulfills a specific function, on the one hand the chylomicrons are responsible for transferring phospholipids, triglycerides and cholesterol from the intestine to the tissues, which are acquired through food intake. For their part, VLDL are synthesized by the liver and are responsible for transporting triglycerides to extrahepatic tissues. IDLs are compounds that are located in the blood in very small amounts, not to mention the fact that their duration is very short. LDLs are molecules made up of cholesterol bound to protein. Finally, HDLs are in charge of transferring cholesterol from body tissues to the liver.
