How does the concentration of lipids in a lipoprotein relate to its density?

The relationship between the concentration of lipids in a lipoprotein and its density is inversely proportional. As the concentration of lipids increases, the density of the lipoprotein decreases. This is primarily due to the structural composition of lipoproteins, which are made up of varying proportions of lipids (fats) and proteins.

Lipoproteins can be thought of as spherical complexes that transport lipids through the bloodstream. They consist of a core of triglycerides and cholesterol esters, surrounded by a shell of phospholipids and apoproteins. When the lipid concentration increases—meaning there is a higher ratio of lipids to proteins—the overall density of the lipoprotein decreases, resulting in a lighter particle.

For example, chylomicrons, which are high in triglycerides, have a low density compared to high-density lipoproteins (HDL), which have higher protein content and thus are denser. This dynamic is why the concentration of lipids directly correlates to the density of the lipoprotein, leading to the conclusion that a greater concentration of lipids results in lower density.