This excerpt is from an animation explaining the functions of lipoproteins.

A lipoprotein (as displayed above in simple/stylised form) is a biochemical assembly that contains both proteins and lipids whose function is to transport water-insoluble lipids in the water-based bloodstream. The lipids or their derivatives may be covalently or non-covalently bound to the proteins. Many enzymes, transporters, structural proteins, antigens, adhesins and toxins are lipoproteins. Examples include the high density (HDL) and low density (LDL) lipoproteins which enable fats to be carried in the blood stream, the transmembrane proteins of the mitochondrion and the chloroplast, and bacterial lipoproteins.