How is cholesterol transported?
Cholesterol is transported by complex particles, called lipoproteins, which have specific proteins on their surface. These proteins, called apolipoproteins, have an essential function in the metabolism of lipoproteins.
What is the primary transport of cholesterol?
LDLs
LDLs are the primary plasma carriers of cholesterol for delivery to all tissues. LDL can be absorbed by the liver and other tissues via receptor mediated endocytosis.
Does LDL transport cholesterol?
Plasma low density lipoprotein (LDL) transports cholesterol from liver to peripheral tissues including the adrenal glands and gonads.
How is cholesterol transported from the liver to peripheral tissues?
Chylomicrons. These are large triglyceride rich particles made by the intestine, which are involved in the transport of dietary triglycerides and cholesterol to peripheral tissues and liver.
How is cholesterol transported across cell membranes?
Most cholesterol is transported in the blood as cholesteryl esters in the form of lipid-protein particles known as low-density lipoproteins (LDL) (Figure 13-43). When a cell needs cholesterol for membrane synthesis, it makes transmembrane receptor proteins for LDL and inserts them into its plasma membrane.
Does cholesterol use active transport?
Cholesterol turnover is normally balanced by cholesteryl ester formation at cholesterol excess and cellular cholesterol efflux by both passive and active transport.
What is responsible for transporting cholesterol to organs?
HDL plays an important role in transporting cholesterol from the peripheral tissues to the liver, where it can be excreted; this process is known as reverse cholesterol transport (RCT). (The liver is the main organ for excretion of cholesterol, doing so either directly or by converting cholesterol into bile acids.)
What protein transports cholesterol?
Cholesterol is dynamically transported among membrane-bound organelles primarily by nonvesicular mechanisms. Sterol transfer proteins (STPs) bind cholesterol in their hydrophobic pockets and facilitate its transfer across the aqueous cytosol.
What helps reverse cholesterol transport?
Reverse cholesterol transport is a multi-step process resulting in the net movement of cholesterol from peripheral tissues back to the liver via the plasma compartment. Cellular cholesterol efflux is mediated by HDL, acting in conjunction with the cholesterol esterifying enzyme, lecithin: cholesterol acyltransferase.
What role does cholesterol play in the cell membrane?
Cholesterol is essential for making the cell membrane and cell structures and is vital for synthesis of hormones, vitamin D and other substances. Cell membrane synthesis – Cholesterol helps to regulate membrane fluidity over the range of physiological temperatures.
Is cholesterol passive or active transport?
Only “active” cholesterol molecules outside of cholesterol-rich regions and partially exposed in water phase are able to fast transfer. The dissociation of partially exposed cholesterol molecules in water determines the rate of passive aqueous diffusion of cholesterol out of plasma membrane.