Cholesterol is found in many foods and can also be made by the liver through a series of enzyme-catalysed reactions. To avoid increased risks of heart disease, cholesterol levels must be tightly regulated. In healthy individuals, cholesterol is only produced by the liver when blood cholesterol levels are low. In certain individuals, the body fails to regulate cholesterol production because of a mutation in one of the enzymes involved in the biochemical pathway responsible for synthesizing cholesterol, resulting in an overproduction of cholesterol. Explain a mechanism for how this mutation might result in excess cholesterol production.
A mutation of the LDLR gene (a gene that encodes low-density lipoproteins receptors) changes the way the receptors develop, either in number or structure. As a result, cholesterol does not penetrate cells and circulates in the blood. Therefore, blood cholesterol is high while intracellular cholesterol is low. Since the production of cholesterol in cells is not inhibited by the exogenous cholesterol, cells produce endogenous cholesterol increasing the normal levels of cholesterol in the blood. Such mutations are associated with the genetic diseases referred to as familial hypercholesterolaemia.
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