HDL practical

Question 1

What does the content of high density lipoproteins (HDL) look like?

Answer 1

High protein content

Question 2

What does the content of light density lipoproteins (LDL) look like?

Answer 2

High cholesterol content

Question 3

What does HDL do?

Answer 3

Picks up cholesterol from along the arteries, returns it to the liver for excretion

Question 4

What does LDL do?

Answer 4

Deposits cholesterol as plaques

Question 5

What is the formation of arterial plaque (LDL) associated with?

Answer 5

Cornoary heart disease and stroke

Question 6

What do high levels of HDL and LDL mean?

Answer 6

High HDL = protective
High LDL = requires treatment (dietary, lifestyle, drug)

Question 7

How is cholesterol estimated?

Answer 7

A coupled enzyme reaction

Question 8

What does the first enzyme do?

Answer 8

Releases all the cholesterol so it can be measured

Question 9

What does the second enzyme do?

Answer 9

Oxidases cholesterol, forming hydrogen peroxide (H²O²). Each cholesterol molecule produces one molecule of H²O²

Question 10

What does the third enzyme do?

Answer 10

Releases atomic oxygen from the H²O² reacting with phenol + 4-aminoantipyrine and produces a red quinoneimine dye

Question 11

What does the amount of red colour produced equal to?

Answer 11

The amount of cholesterol, when measured at 500nm

Question 12

What are the products and reactants of enzyme one?

Answer 12

Reactants = Cholesterol-ester, H²O
Products = Cholesterol, fatty acids

Question 13

What are the products and reactants of enzyme two?

Answer 13

Reactants = Cholesterol, O²
Products = Cholestene-3-one, H²O²

Question 14

What are the products and reactants of enzyme three?

Answer 14

Reactants = 2H²O², Phenol, Animoantipyrine
Products = Quinoneimine, H²O

Question 15

What are the three enzymes used?

Answer 15

1 = Cholesterol esterase
2 = Cholesterol oxidase
3 = Peroxidase

Question 16

What solution is added to determine how much of the cholesterol is HDL?

Answer 16

A phosphotungstic acid/MgCl

Question 17

How does the solution separate HDL and LDL cholesterol?

Answer 17

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

Question 18

How to work out the concentration of an unknown sample?

Answer 18

concentration of standard x absorbance of unknown/absorbance of standard

Question 19

What are the desirable and high cholesterol parameters?

Answer 19

Desirable = < 5.17 mmol/L
Borderline high = 5.17 - 6.19 mmol/L
High = > 6.20 mmol/L (inc. 6.20)

Question 20

What are high and low risks of CHD in HDL levels?

Answer 20

High = < 1.04 mmol/L
Low = > 1.55 mmol/L (inc. 1.55)

Question 21

What other tests can be used to test for cornorary heart disease?

Answer 21

ECG
X-rays
MRI scans
CT scans

Question 22

What level does LDL have to be over to suggest statin treatment?

Answer 22

4.92 mmol/L

Question 23

What does lipanemia mean?

Answer 23

Excess of lipoproteins in bloo, causes increased absorbance of light when measuring absorbance