Lipids 3.

Question 1

mention the general specimen requirements for lipid analysis

Answer 1

1. Serum or plasma is collected after at least 12 hour fast for total cholesterol testing
   (if analysis is delayed, the serum or plasma can be refregerated at 4 degrees celciuos for several days.

Question 2

Explain the cholesterol enzymatic method abell-kendell cholesterol analysis.

Answer 2

1.The enzyme cholesteryl ester hydrolase cleaves the fatty acid residue from cholesteryl esters
2. Cholesterol is reacted by the second enzyme, cholesterol oxidase, producing hydrogen peroxide (H_2 O_2)
3. Hydrogen peroxide reacts with a colorless compounds into colored compound
4. Absorbance is measured at about 500 nm wavelength

Question 3

what are the compounds that interferes with abell-kendell cholesterol analysis.

Answer 3

1. Bilirubin
2. Ascorbic acid
3. Hemoglobin

Question 4

What role does lipase play in the enzymatic method for measuring serum triglycerides?

Answer 4

Lipase catalyzes the hydrolysis of triglycerides to glycerol and fatty acids. This initial step breaks down the triglycerides into their constituent components.

Question 5

How is glycerol phosphorylated in this enzymatic method, and which compounds are involved?

Answer 5

The freed glycerol resulting from triglyceride hydrolysis is phosphorylated by ATP (adenosine triphosphate). This reaction is catalyzed by an enzyme called glycerokinase. The product of this phosphorylation is glycerophosphate.

Question 6

What is the purpose of glycerokinase in this process?

Answer 6

Glycerokinase is responsible for phosphorylating glycerol using ATP. This conversion to glycerophosphate allows further processing of glycerol in subsequent steps.

Question 7

Describe how glycerophosphate is oxidized and what enzymes catalyze this reaction.

Answer 7

Glycerophosphate is oxidized to dihydroxyacetone and hydrogen peroxide. The enzyme glycerophosphate oxidase facilitates this oxidation process.

Question 8

Explain the significance of hydrogen peroxide’s reaction with a compound producing color in this context

Answer 8

Hydrogen peroxide reacts with a specific compound, resulting in a color change. The intensity of this color change is proportional to the concentration of triglycerides in the sample. By measuring the absorbance of this colored product spectrophotometrically (usually around 500 nm wavelength), we can quantify the triglyceride levels.

Question 9

Why is absorbance measured at about 500 nm wavelength, and what does it indicate?

Answer 9

Absorbance is measured at approximately 500 nm because that wavelength corresponds to the maximum absorbance of the colored product formed during the enzymatic reaction. The higher the absorbance, the greater the concentration of triglycerides in the sample.

Question 10

How can endogenous glycerol affect enzymatic methods for measuring serum triglycerides?

Answer 10

Endogenous glycerol (glycerol naturally present in the sample) can lead to overestimation of serum triglyceride levels. This is because the enzymatic method cannot distinguish between exogenous (from triglycerides) and endogenous glycerol. To correct for this effect, most enzymatic triglyceride assays are “sample blanked,” meaning they subtract the contribution of endogenous glycerol from the total glycerol measurement.

Question 11

What does “sample blanked” mean, and why is it necessary in most enzymatic triglyceride assays?

Answer 11

“Sample blanked” refers to subtracting the background signal (endogenous glycerol) from the total signal obtained in the assay. By doing so, we eliminate the interference caused by endogenous glycerol and obtain a more accurate measurement of triglyceride levels.

Question 12

All no HDL-lipoproteins are first precipitated out by which chemicals

Answer 12

1. Magnesium
2. Soldium phosphotugstate
3. Dextran sulfate
4. Heparin sulfate
5. Phosphotungsten

Question 13

How are precipitates sedimented

Answer 13

1. By centrifugation at 1,500g for 10-30 mins

Question 14

How is LDL cholestelol calculated

Answer 14

LDL chol=(total cholesterol) - (HDL chol)-(Trigelyceride)/5

Question 15

explain the factor trigericeride/5

Answer 15

5 is an estimate of VLDL cholesterol concentration that is based on the average ratio of triglyceride to cholesterol in VLDL

Question 16

When should the friedewald equation not be used

Answer 16

1. Samples contain triglyceride concentrations above 400mg/dl
2. Samples with significant amounts of chylomicrons
3. Patients have dysbetalipoproteinemia

Question 17

what is the high sensitive C reactive protein

Answer 17

Is a test first described in bacterial infections and routinely monitored as an indication of infection and autoimmune disease

Question 18

what does increased serum C reactive protein (CRP) indicate

Answer 18

1. Risk of coronary artery disease
2. Cerebrovascular disease
3. Peripheral arterial disease

Question 19

What does CRP depend on

Answer 19

It depends on the amplification of the light scattering properties of the antigen-antibody complex coupled to a latex particle