Medical Lab Techniques: Clinical Biochemistry Lab 4

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Questions and Answers

What is included in a typical lipid profile?

HDL cholesterol, triglycerides, vitamin D, and LDL cholesterol

Total cholesterol, HDL cholesterol, triglycerides, and LDL cholesterol (correct)

Total cholesterol, triglycerides, vitamin K, and HDL cholesterol

Total cholesterol, HDL cholesterol, triglycerides, and blood glucose

What role does cholesterol play in the body?

It helps in the absorption of vitamins exclusively

It supports the production of hormones and aids in digestion (correct)

It is used solely for cell membrane structure

It mainly acts as an energy source for cells

What percentage of cholesterol in the body is synthesized by the liver?

70% (correct)

50%

30%

100%

What is LDL cholesterol known as?

Bad cholesterol Signup and view all the answers

Which of the following is true regarding HDL cholesterol?

It transports cholesterol away from the arteries to the liver Signup and view all the answers

What health condition is associated with high levels of LDL cholesterol?

Atherosclerosis Signup and view all the answers

Which of the following foods is likely to contribute to higher cholesterol levels?

Meat and dairy products Signup and view all the answers

What is the primary target for cholesterol-lowering medications?

Reducing LDL levels Signup and view all the answers

What is the incubation time at 37 oC for the sample and standard?

5 minutes Signup and view all the answers

At what wavelength should the absorbance be measured?

505 nm Signup and view all the answers

What is the appropriate procedure after mixing the precipitant and sample?

Centrifuge for 10 minutes Signup and view all the answers

Which lipoproteins are targeted for precipitation in the HDL cholesterol estimation?

VLDL, LDL, and lipoprotein(a) Signup and view all the answers

What is the total volume of the standard used in the HDL estimation procedure?

200 μl Signup and view all the answers

What is the temperature condition for incubation at room temperature?

10 minutes Signup and view all the answers

What is the main enzyme used to hydrolyze cholesterol esters in serum?

Cholesterol esterase Signup and view all the answers

What is produced when cholesterol is oxidized by cholesterol oxidase?

Cholest-4-en-3-one Signup and view all the answers

What substance is used for the precipitation of lipoproteins?

Phosphotungstic acid/MgCl2 Signup and view all the answers

What is done with the supernatant after centrifuging?

It is analyzed for cholesterol Signup and view all the answers

What is the final product of the reaction that involves hydrogen peroxide, phenol, and 4-aminoantipyrine?

Quinoneimine dye Signup and view all the answers

How is the concentration of cholesterol in serum measured in this method?

By the intensity of the red color formed Signup and view all the answers

Which component is not part of the enzymatic assay for cholesterol measurement?

VLDL Signup and view all the answers

What is the purpose of labeling test tubes as test (T), standard (S), and blank (B)?

To differentiate sample types for measurement Signup and view all the answers

What is the purpose of the cholesterol reagent in the experiment?

To measure the absorbance of HDL cholesterol Signup and view all the answers

What volume of monoreagent is added to each of the test tubes?

1000 μl Signup and view all the answers

At what temperature can the tubes be left to stand for the colorimetric measurement?

Room temperature for 10 minutes or 37°C for 5 minutes Signup and view all the answers

What should be measured at a wavelength of 500 nm?

The absorbance of the supernatant and standard Signup and view all the answers

What does the calculation for HDL Cholesterol involve?

The absorbance of the supernatant divided by the absorbance of the standard Signup and view all the answers

Which component is not included in the blank tube during the experiment?

Standard Signup and view all the answers

What total cholesterol level is categorized as 'High'?

240mg/dL and above Signup and view all the answers

Which LDL cholesterol level is considered 'Optimal'?

Less than 100mg/dL Signup and view all the answers

What is the implication of an HDL cholesterol level less than 40 mg/dL?

A major risk factor for heart disease Signup and view all the answers

When are direct LDL measures typically used?

When triglycerides exceed 400 mg/dL Signup and view all the answers

How is VLDL typically estimated?

By dividing total triglycerides by five Signup and view all the answers

What LDL cholesterol level is categorized as 'High'?

160-189 mg/dL Signup and view all the answers

What is the estimated VLDL error margin when triglycerides are above 400 mg/dL?

High error margin Signup and view all the answers

Which total cholesterol level is categorized as 'Borderline high'?

200-239 mg/dL Signup and view all the answers

Study Notes

Lipid Profile and Cholesterol Overview

Lipid profile assesses levels of total cholesterol, HDL, triglycerides, and LDL.
Cholesterol is a vital fatty substance present in every cell, contributing to hormone production and digestion.
Around 70% of body cholesterol is synthesized in the liver while 30% comes from dietary sources (meat, eggs, dairy).
High dietary fat intake can increase liver cholesterol production.

Types of Cholesterol

LDL (Low-Density Lipoprotein):
- Known as "bad" cholesterol; carries cholesterol from the liver to the bloodstream.
- Lower protein content with higher cholesterol levels, prone to sticking to blood vessel walls.
- High LDL levels are linked to atherosclerosis and heart disease, making its reduction a treatment target.
HDL (High-Density Lipoprotein):
- Considered "good" cholesterol, helps protect against heart disease.
- Higher levels are desirable; below 40 mg/dL is a major heart disease risk factor.

Normal Cholesterol Values

Total Cholesterol:
- Desirable: Less than 200 mg/dL.
- Borderline high: 200-239 mg/dL.
- High: 240 mg/dL and above.
LDL Cholesterol:
- Optimal: Less than 100 mg/dL.
- Near optimal: 100-129 mg/dL.
- High: 160-189 mg/dL.
- Very High: 190 mg/dL and above.
HDL Cholesterol:
- Protective: 60 mg/dL and higher.
- The higher, the better: 40-59 mg/dL.
- Major risk factor: Less than 40 mg/dL.

LDL Measurement and Calculation

Total cholesterol is the sum of HDL, LDL, and VLDL.
VLDL is estimated as one-fifth of triglycerides; Direct LDL measures are used for triglyceride levels over 400 mg/dL.
Friedewald formula:
- Estimated LDL = Total cholesterol - (HDL + TG/5)

Estimation of Serum Cholesterol

Method: Enzymatic colorimetric method.
Principle: Cholesterol esterase hydrolyzes cholesterol esters into free cholesterol and fatty acids, followed by oxidation by cholesterol oxidase.
The resultant hydrogen peroxide forms a red dye, which is quantitatively measured.

Steps for Cholesterol Estimation

Utilize labeled test tubes for test, standard, and blank.
Add reagents accordingly, incubate, then measure absorbance at 505 nm.
Calculation formula:
- Cholesterol (mg/dL) = (A_sample / A_standard) x (standard concentration)

Estimation of HDL Cholesterol

Method: Combination of separation and enzymatic colorimetric method.
Principle: VLDL and LDL are precipitated with phosphotungstic acid/MgCl2, leaving HDL in the supernatant for analysis.

Steps for HDL Estimation

Prepare test tubes for precipitation and colorimetric analysis.
Incubate and centrifuge to obtain clear supernatant.
Measure absorbance at 500 nm and calculate using:
- HDL Cholesterol (mg/dL) = (A_supernatant / A_standard) x (standard concentration)

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Description

This quiz focuses on Normal Values for Total Cholesterol Levels in Clinical Biochemistry. Students will evaluate different cholesterol categories based on specified thresholds. Ideal for second-stage medical laboratory technique students.