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Updated August 12, 2014

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A low density lipoprotein (LDL) particle

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Definition: Lipoproteins are complex particles consisting of proteins and fats that circulate in the bloodstream. The chief purpose of lipoproteins is to transport fats -- mainly cholesterol and triglycerides - from place to place through the bloodstream.

Fats are insoluble (they do not dissolve in water) so they have to be "packaged" in such a way that they can flow through the bloodstream. Lipoproteins form a container, made of specialized proteins called apolipoproteins, which enclose the fats, allowing them to be transported to their appropriate destinations.

Examples of Lipoproteins:

Chylomicrons are lipoproteins that deliver triglycerides from the intestines to the liver, muscle, and adipose (fat) tissue. The main apolipoprotein of chylomicrons is APO B-48.

LDL (low density lipoproteins) carry cholesterol from the liver to tissues in the body.  The main apolipoprotein of LDL is APO B-100

HDL (high density lipoproteins) carry excess cholesterol from the body's tissues back to the liver. The main apolipoprotein of HDL is APO-A.


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