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Cholesterol

Higher Human Biology. Cholesterol. Lipids Group of organic compounds Simple – fats (saturated and unsaturated) Complex (steroids). Cholesterol. Needed by the body for various reasons Component of cell membranes Produced in the liver from saturated fats from normal diet.

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Cholesterol

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  1. Higher Human Biology Cholesterol

  2. Lipids • Group of organic compounds • Simple – fats (saturated and unsaturated) • Complex (steroids)

  3. Cholesterol • Needed by the body for various reasons • Component of cell membranes • Produced in the liver from saturated fats from normal diet

  4. Transport of Cholesterol • Lipoproteins • Found in blood plasma • Molecules containing a combination of lipids and protein • Transport lipids from one part of the body to another

  5. Low-density lipoprotein (LDL) • Cholesterol transported to body cells by LDLs produced in the liver • Most body cells synthesis LDL receptors which are found in their cell membranes • After attachment to a receptor • cell engulfs LDL-Cholesterol • Cholesterol released for use by the cell

  6. Atherosclerosis • Negative feedback plays a role • Inhibits production of new LDL-receptors when the cell has enough cholesterol • Less of LDL-cholesterol circulating in bloodstream is absorbed by body cells • Can become absorbed by endothelium of artery • Atheroma

  7. More likely to occur if; • Person eats a diet rich in saturated fat • Suffers from familial hypercholesterolaemia

  8. High-density lipoprotein (HDL) • Some excess cholesterol is transported by HDL from body cells to liver for elimination • Prevents high level of cholesterol accumulating in bloodstream • Is not taken into artery walls • Does not contribute to atheroma

  9. A higher ratio of HDL to LDL will result in lower blood cholesterol and a reduced chance of atherosclerosis.

  10. Regular physical activity tends to raise HDL levels • Dietary changes aim to reduce the levels of total fat in the diet and to replace saturated with unsaturated fats. • Drugs such as statins reduce blood cholesterol by inhibiting the synthesis of cholesterol by liver cells.

  11. Familial Hypocholesterolaemia • Familial hypercholesterolaemia is an inherited condition • The level of low-density lipoprotein (LDL) cholesterol in the blood is higher than normal from birth • It is caused by a defect in a gene which controls the way cholesterol is handled in the body • As a result of the defect, LDL receptor number is reduced or the structure altered. This stops the LDL from unloading its cholesterol into the cell. LDL cholesterol is not broken down properly and builds up in the bloodstream.

  12. In most cases the defective gene is inherited from one parent (heterozygous inheritance, autosomal) • Results in the development of heart disease at a young age. • This is caused by plaques of atheroma developing within the walls of the coronary (heart) arteries

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