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23 Cards in this Set
- Front
- Back
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Is cholesterol responsible for CHD?
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increase cholesterol leads to icncreased CHD (4 fold if up by 4mg)
- Some claim the country has high serum concentrations and increased saturated fats but they are at no greater risk of CHD - however science largely opposes this |
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What is one of the leading causes of heart disease?
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- Cholesterol
- Children as young as 9 can have hypercholesterolaemia leading to heart diseaese. - However 90% of cholesterol is sysnthesised in the body and there has been no reduction in deaths due to it since the intro of statins |
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What is the structure of cholesterol?
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- Aliphatic side chain
- Rings A& B are hydrophillic - Rings C& D are hydrophobic - A and B are the outward parts of he membrane and C&D are towards the centre of the plasma membrane |
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How is Cholesterol measured?
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Cholesterol esterase Bound cholesterol --------------------------- Free cholesterol Cholesterol esterase frees the bound cholesterol Cholesterol oxidase Cholesterol ------------------------------- cholest-4-ene-3-one + H2O2 Cholesterol oxidase normally generates H2O2 which is used to measure colour change (to give a value for total cholesterol) |
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What are the issues with measuring only total cholesterol?
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Total cholesterol levels dont tell you anything - it is just a number - it would be much more helpful to know the values of LDLs and HDLs.
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What are normal plasma cholesterol concentrations?
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Total cholesterol: >= 5 mmol/L
Cholesterol: HDL ratio: >= 4 mmol/L HDL cholesterol: >= 1 mmol/L
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What are the properties of cholesterol?
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White fat like substance only found in animals
Not essential nutrient in the body as we can synthesise our own mainly in the liver and intestinal mucosa - thus must be important for the endocrine system - particularly steroid hormone formation - bile salts acid formation, vitamin D and cell membrane regulation. |
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What steriod hormones are derived from cholesterol?
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1) Aldosterone: Important in kidney functioning, fat and protein degratation
2) Cortisol: Activates gluconeogenesis, fat and protein degradation 3) Androsterone: Important in the synthesis of male and female sex hormones, androgens and oestrogen. |
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Explain bile acid synthesis
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Hydrophillic derivatives of cholesterol - synthesised in the liver and stored in the galbladder
- It is secreted during digestion into the upper small intestine increasing the surface area of fats so the intestinal fluids can work on them - Reabsorbed in the lower intestine following this it is returned to the enteric circulation - Detergents are used to emulsify the fats in the galbladder. |
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What amount of bile acids are synthesised per day?
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400 mg
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What are some examples of bile acids?
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Lithocholate, deoxycholate, cholae ad chenodeoxycholate of which the later two are usually bound to taurine / glycine
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What is used if you cant tollerate statins?
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Drugs which prevent the re-uptake of bile acids.
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What is vitamin D?
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A group of vitamins found in liver and fish oils, essential for the absorption of calcium and the prevention of rickets in children and osteomalacia in adults. The greatest source is from sunlight
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What is the relationship between vitamin D and cholesterol?
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Cholesterol is a precursor of vitamin D
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What action does sunlight have in terms of vitamin D?
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The action of sunlight opens up the rings C and B in the structure which is thought to increase the permeability of the plasma membrane to calcium leading to increased intestinal absorbance of calcium and increased PTH mediated bone resorption and decreased renal calcium and phosphate reabsorption.
Also used for blood pressure regulation and regulation of cell growth and immunoduration. |
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What is the role of cholesterol in membranes?
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Essential component of cell membranes.
Fits awkwardly into the lipid bilayer causing membrane disruption leading to ridgidity and less deformity. It immobilises in first few hydrocarbon groups of phospholipid bilayer molecules making it less deformable and decreases permeability to small water soluble molecules |
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What percentage of choleserol constitutes to lipid content and what does this enable?
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Constitutes up to 25% of lipid content in some membranes. This means that erythrocytes can move through capillaries and return to their original shape, without cholesterol this wouldnt be possible
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What would be needed in human cells if they didnt have cholesterol?
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Would require a cell wall to regulate cellular processes - the whole biochemistry of the cell would change
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What happens to cells when there is increased levels of cholesterol?
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Islands of cholesterol bilayers form - the membrane becomes more ridgid meaning there is a decrease in the mobility of polar lipids into cells.
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How is cholesterol synthesised?
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Acetate to mevalonate to isophrenoid to squalene to cyestine
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What cholesterol lowering treatments are available?
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-Statins
- Simvastatin - Provastatin |
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How do statins work?
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Act to inhibit HMG coA reductase to increase the action of LDL receptors on the cell surface to increase LDL clearance. The medicines actually act to replace the HMG-CoA that exists in the liver, thereby slowing down the cholesterol production process.
Liver cells either synthesis or remove cholesterol from the circulation. Of which stains block synthesis thus liver cells add receptors to their surface thus circulating levels of cholesterol will reduce. |
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What are the side effects of Statins?
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- Flactulance
- Sleep disorders - Diarrhoea - Can effect liver functioning by interfering with cell signalling - Plyotrophic effects e.g. Prevent atherosclerosis - Increased nitric oxide impairs blood flow thus decreases platelet activity inhibiting coag pathway. |
