MLPAO Clinical Chemistry Fundamentals 1 — Questions and Answers
Question 1: Which enzyme is considered the most specific marker for myocardial infarction when measured in serum?
- Creatine kinase-MB (CK-MB)
- Troponin I (Correct answer)
- Lactate dehydrogenase (LD)
- Aspartate aminotransferase (AST)
Correct answer: Troponin I
Troponin I is the most specific cardiac biomarker for myocardial infarction. While CK-MB was historically used, troponin I is found almost exclusively in cardiac muscle and remains elevated for a longer period, making it the gold standard for MI diagnosis.
Question 2: What is the primary buffer system in human blood plasma?
- Phosphate buffer system
- Bicarbonate-carbonic acid buffer system (Correct answer)
- Protein buffer system
- Hemoglobin buffer system
Correct answer: Bicarbonate-carbonic acid buffer system
The bicarbonate-carbonic acid buffer system is the primary buffer in blood plasma, maintaining pH between 7.35 and 7.45. This system is regulated by both the lungs (CO2 excretion) and kidneys (bicarbonate reabsorption), making it highly effective at maintaining acid-base balance.
Question 3: A patient presents with a serum sodium of 128 mmol/L. Which condition is this most consistent with?
- Hypernatremia
- Hyponatremia (Correct answer)
- Hyperkalemia
- Metabolic alkalosis
Correct answer: Hyponatremia
A serum sodium of 128 mmol/L is below the normal reference range of 136-145 mmol/L, indicating hyponatremia. This condition can result from excessive water retention, sodium loss, or conditions such as SIADH, and may present with neurological symptoms.
Question 4: Which method is most commonly used for measuring serum glucose in clinical chemistry analyzers?
- Hexokinase method (Correct answer)
- Folin-Wu method
- Ortho-toluidine method
- Somogyi-Nelson method
Correct answer: Hexokinase method
The hexokinase method is the reference method for glucose measurement. It uses hexokinase to phosphorylate glucose to glucose-6-phosphate, which is then oxidized by glucose-6-phosphate dehydrogenase with production of NADPH, measured spectrophotometrically.
Question 5: What does an elevated serum creatinine level primarily indicate?
- Liver dysfunction
- Decreased glomerular filtration rate (Correct answer)
- Muscle inflammation
- Dehydration only
Correct answer: Decreased glomerular filtration rate
Elevated serum creatinine primarily indicates decreased glomerular filtration rate (GFR) and impaired kidney function. Creatinine is a byproduct of muscle metabolism that is freely filtered by the glomerulus and not significantly reabsorbed, making it a useful marker for renal function.
Question 6: Which lipoprotein is considered 'good cholesterol' due to its role in reverse cholesterol transport?
- Low-density lipoprotein (LDL)
- Very low-density lipoprotein (VLDL)
- High-density lipoprotein (HDL) (Correct answer)
- Chylomicrons
Correct answer: High-density lipoprotein (HDL)
HDL is considered 'good cholesterol' because it participates in reverse cholesterol transport, carrying cholesterol from peripheral tissues back to the liver for excretion. Higher HDL levels are associated with reduced cardiovascular risk.
MLPAO Clinical Chemistry Fundamentals 1
Which enzyme is considered the most specific marker for myocardial infarction when measured in serum?