Low-density lipoprotein degradation. Computer illustration showing the degradation of a low-density lipoprotein molecule (LDL). When there are high levels of LDL cholesterol in the blood it builds up on the sides of blood vessels hardening them, a condition named atherosclerosis. This narrows the blood vessels and may block them. LDL receptors in cell membranes recognise and bind to LDL molecules to remove them from the bloodstream. The LDL and receptor are absorbed by the cell and destroyed.