Cholesterol is essential for the functioning of plasma membranes where it plays two main roles. Firstly it limits the uncontrolled leakages of small molecules [water and ions] in and out of plasma membrane. The cell can thus control the passage of solutes and ions using specialized membrane proteins and without wasting energy to counteracts their leakage. Cholesterol is an important constituent of myelin and helps to prevent the outward flow of ions which would ‘short circuit’ the movement of nerve impulses along axon.
Cholesterol is also used by the liver for making bile salts which plays part in digestive system and, in small quantities, is used to make steroid hormones in ovaries, testes and adrenal glands.
However, cholesterol is insoluble in water but can be carried in the blood plasma in the form of lipoproteins. The balance of these lipoproteins is usually maintained by special receptors in the liver cells but saturated fats like ones in ‘mutura’ decrease their activity and hence lead to a rise in plasma cholesterol. This can lead to heart attacks [from blocking of coronary arteries], strokes [brain arteries blocked] or blockages of arteries in the legs.