Download 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
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
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
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
 More likely to occur if;
 Person eats a diet rich in saturated fat
 Suffers from familial hypercholesterolaemia
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
 A higher ratio of HDL to LDL will result in
lower blood cholesterol and a reduced
chance of atherosclerosis.
 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.
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.
 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