HDL practical Flashcards
What does the content of high density lipoproteins (HDL) look like?
High protein content
What does the content of light density lipoproteins (LDL) look like?
High cholesterol content
What does HDL do?
Picks up cholesterol from along the arteries, returns it to the liver for excretion
What does LDL do?
Deposits cholesterol as plaques
What is the formation of arterial plaque (LDL) associated with?
Cornoary heart disease and stroke
What do high levels of HDL and LDL mean?
High HDL = protective
High LDL = requires treatment (dietary, lifestyle, drug)
How is cholesterol estimated?
A coupled enzyme reaction
What does the first enzyme do?
Releases all the cholesterol so it can be measured
What does the second enzyme do?
Oxidases cholesterol, forming hydrogen peroxide (H²O²). Each cholesterol molecule produces one molecule of H²O²
What does the third enzyme do?
Releases atomic oxygen from the H²O² reacting with phenol + 4-aminoantipyrine and produces a red quinoneimine dye
What does the amount of red colour produced equal to?
The amount of cholesterol, when measured at 500nm
What are the products and reactants of enzyme one?
Reactants = Cholesterol-ester, H²O
Products = Cholesterol, fatty acids
What are the products and reactants of enzyme two?
Reactants = Cholesterol, O²
Products = Cholestene-3-one, H²O²
What are the products and reactants of enzyme three?
Reactants = 2H²O², Phenol, Animoantipyrine
Products = Quinoneimine, H²O
What are the three enzymes used?
1 = Cholesterol esterase
2 = Cholesterol oxidase
3 = Peroxidase
What solution is added to determine how much of the cholesterol is HDL?
A phosphotungstic acid/MgCl
How does the solution separate HDL and LDL cholesterol?
It causes LDL and VLDL lipoproteins to precipitate, so when centrifuged they go to the bottom of the test tube, leaving HDL dissolved in supernatent
How to work out the concentration of an unknown sample?
concentration of standard x absorbance of unknown/absorbance of standard
What are the desirable and high cholesterol parameters?
Desirable = < 5.17 mmol/L
Borderline high = 5.17 - 6.19 mmol/L
High = > 6.20 mmol/L (inc. 6.20)
What are high and low risks of CHD in HDL levels?
High = < 1.04 mmol/L
Low = > 1.55 mmol/L (inc. 1.55)
What other tests can be used to test for cornorary heart disease?
ECG
X-rays
MRI scans
CT scans
What level does LDL have to be over to suggest statin treatment?
4.92 mmol/L
What does lipanemia mean?
Excess of lipoproteins in bloo, causes increased absorbance of light when measuring absorbance
