Illustration of the structure of a low-density lipoprotein (LDL) particle, a form of cholesterol found in the blood. Chemically mainly made up of lipids, this complex structure includes carrier proteins (pink) known as apo-B proteins, which assist LDL transport in the blood. Also found in the outer coat are phospholipids (green) and free cholesterol molecules (yellow). Within the core, cholesterol molecules (yellow) are bound into long esters by fatty acid chains (red). Cardio-vascular research points to LDL particles, in high levels in the blood, leading to an increased risk of narrowing of the arteries (atherosclerosis), coronary heart disease and stroke.