Lipoproteins and Apolipoproteins - Structure , function and metabolism : Usmle step 1 Biochemistry
Lipoproteins and Apolipoproteins - Structure and function Animation : Usmle step 1 Biochemistry
A group of proteins synthesized in the small intestine and liver that transport hydrophobic lipids such as cholesterol, triglycerides, and phospholipids throughout the body. Types are named based on the density of their contents and include very-low- (VLDL), low- (LDL), intermediate- (IDL), and high-density lipoproteins (HDL).
Apolipoproteins are proteins that bind lipids (oil-soluble substances such as fat and cholesterol) to form lipoproteins. They transport lipids (and fat soluble vitamins) in blood, cerebrospinal fluid and lymph.
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The lipid components of lipoproteins are insoluble in water. However, because of their detergent-like (amphipathic) properties, apolipoproteins and other amphipathic molecules (such as phospholipids) can surround the lipids, creating a lipoprotein particle that is itself water-soluble, and can thus be carried through water-based circulation (i.e., blood, lymph).
In addition to stabilizing lipoprotein structure and solubilizing the lipid component, apolipoproteins interact with lipoprotein receptors and lipid transport proteins, thereby participating in lipoprotein uptake and clearance. They also serve as enzyme cofactors for specific enzymes involved in the metabolism of lipoproteins.
Apolipoproteins are also exploited by hepatitis C virus (HCV) to enable virus entry, assembly, and transmission. They play a role in viral pathogenesis and viral evasion from neutralizing antibodies
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