Which of the following statements about High Density Lipoprotein (HDL) is false –
Correct Answer: HDL increases oxidation of LDL
Description: Ans. A. HDL increases oxidation of LDL The reverse cholesterol transport system:-a. HDL serves as a chemical shuttle that transports excess cholesterol from peripheral tissues to the liver. This pathway is called the reverse cholesterol transport system. In this system, plasma HDL takes up cholesterol from the peripheral tissues, such as fibroblasts and macrophages.b. This may occur by passive diffusion or may be mediated by the adenosine triphosphate (ATP) - binding cassette transporter 1. The latter interacts directly with free Apo A-1, generating nascent, or so-called discoidal, HDL. Cholesterol undergoes esterification by lecithin-cholesterol acyltransferase (LCAT) to produce cholesteryl ester, which results in the production of the mature spherical HDL.c. Cholesterol is also taken up from triglyceride-rich lipoproteins in a process mediated by a phospholipid transfer protein (ie, CETP).d. Cholesterol is then returned to the liver by multiple routes. In the first route, cholesterol esters may be transferred from HDL to the Apo B-containing lipoproteins, such as very low-density lipoprotein (VLDL) or intermediate-density lipoprotein (IDL), by CETP. These lipoproteins undergo metabolism and subsequent uptake by the liver, primarily by a process mediated by the B, E receptor.e. In the second route, HDL particles may be taken up directly by the liver. In the third, free cholesterol may be taken up directly by the liver. Finally, HDL cholesterol esters may be selectively taken up via the scavenger receptor SR-B1.
Category:
Biochemistry
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