Cholesterol and atherosclerosis. Illustration of a molecular model of cholesterol (yellow), with a human figure and a cutaway view of a coronary artery with a build up of fatty deposits (atheroma, yellow) on its wall in a case of atherosclerosis. Cholesterol is a sterol, a type of lipid, a class of biochemical compounds that includes fats. Cholesterol is an essential component of the cell membranes in mammals, and levels of cholesterol in the blood is an important health indicator. Blocked or narrowed arteries in coronary artery disease can cause heart attacks.