Medical Laboratory Technician Exam Medical Laboratory Technician Clinical Chemistry Procedures 1

Question 1

Which colorimetric method is the standard clinical laboratory procedure for measuring total protein in serum, based on the reaction of peptide bonds with copper ions in alkaline solution?

Accepted Answer

Biuret method

Answer

The biuret method is the standard clinical chemistry procedure for total serum protein. Copper(II) ions in alkaline solution form a violet complex with peptide bonds (two or more), producing a color proportional to protein concentration measured at 540 nm.

Question 2

The van den Bergh reaction used in clinical chemistry laboratories distinguishes between which two fractions of bilirubin?

Accepted Answer

Direct (conjugated) and indirect (unconjugated) bilirubin

Answer

The van den Bergh reaction uses diazonium salts that react directly with conjugated (direct) bilirubin in aqueous solution. Unconjugated (indirect) bilirubin requires addition of an accelerator such as methanol or caffeine to react, allowing differentiation of the two fractions.

Question 3

Ion-selective electrodes (ISE), the most widely used technology for measuring serum electrolytes such as sodium and potassium in clinical chemistry analyzers, operate on which electrochemical principle?

Accepted Answer

Potentiometry — measuring the electrical potential difference across an ion-selective membrane

Answer

ISEs are potentiometric devices; they measure the voltage (potential) that develops across a selective membrane permeable only to the target ion. This potential is proportional to the logarithm of ion activity per the Nernst equation, allowing accurate electrolyte quantification.

Question 4

Hemoglobin A1c (HbA1c) is used in clinical chemistry to assess long-term glycemic control because it reflects average blood glucose over approximately what time period?

Accepted Answer

2 to 3 months

Answer

HbA1c results from non-enzymatic glycation of the beta-chain N-terminal valine of hemoglobin. Because red blood cells survive approximately 120 days, HbA1c reflects the mean blood glucose concentration over the preceding 2–3 months, making it the standard marker for long-term glycemic monitoring.

Question 5

In the uricase (enzymatic) method for measuring uric acid in clinical chemistry, what is the direct product detected to quantify uric acid concentration?

Accepted Answer

Hydrogen peroxide, which reacts with a chromogen via peroxidase to produce a colored product

Answer

Uricase oxidizes uric acid to allantoin and hydrogen peroxide. The H2O2 produced then reacts with a chromogenic oxygen acceptor in the presence of peroxidase (Trinder reaction) to generate a colored compound measured photometrically, providing a specific and sensitive assay.

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Exam Medical Laboratory Technician Clinical Chemistry Procedures 1