Lipids cannot dissolve in plasma unless the body first renders them
water-soluble by combining them with specific proteins. The resultant
particles are called lipoproteins. These come in several sizes and vary in the
amounts of cholesterol and triglyceride they contain. Cholesterol is carried
mainly in low density lipoprotein (LDL) and to lesser extent in high density
lipoprotein (HDL), whereas triglycerides are carried mainly in very low
density lipoprotein (VLDL). Special methods are used to separate these
different lipoproteins so that it is possible to say, for example, whether a
raised plasma cholesterol is due to an increased number of LDL particles or
HDL particles. This distinction is important, as will soon be apparent.