Lipid-carrying particles are collectively known as lipoproteins. Lipoproteins are classified according to their densities. The names of these particles, from least to most dense, are: chylomicrons, very-low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). Most laboratorians are familiar with these particles as many, especially LDL and HDL, are routinely measured in clinical labs. In this course we will not focus on the physiology of all of these particles or the differences between them all. However it is important to understand the basic structure and function of a lipoprotein particle.