BCSE BCSE - Basic and Clinical Sciences Examination Clinical Nutrition and Metabolism Questions and Answers 5 — Questions and Answers
Question 1: Which lipoprotein particle is primarily responsible for reverse cholesterol transport from peripheral tissues to the liver?
- Chylomicron
- VLDL
- LDL
- HDL (Correct answer)
Correct answer: HDL
HDL mediates reverse cholesterol transport by accepting free cholesterol from peripheral cells and delivering it to the liver for excretion or recycling.
Question 2: Carnitine is essential for fatty acid beta-oxidation because it is required for which specific transport step?
- Fatty acid activation to acyl-CoA in the cytoplasm
- Transfer of long-chain acyl groups across the inner mitochondrial membrane (Correct answer)
- Electron transfer in the respiratory chain
- NADH regeneration in the matrix
Correct answer: Transfer of long-chain acyl groups across the inner mitochondrial membrane
Carnitine shuttles long-chain fatty acyl groups across the inner mitochondrial membrane via the carnitine shuttle system so beta-oxidation can occur in the matrix.
Question 3: A newborn presents with cataracts, jaundice, and E. coli sepsis within the first week of life. Which metabolic disorder is most likely?
- Galactosemia (Correct answer)
- Fructosemia
- Maple syrup urine disease
- Glycogen storage disease type I
Correct answer: Galactosemia
Classic galactosemia (GALT deficiency) causes accumulation of galactose-1-phosphate leading to cataracts, liver disease, and predisposition to E. coli neonatal sepsis.
Question 4: Which amino acid is considered conditionally essential during critical illness or injury due to its role in immune function and intestinal integrity?
- Alanine
- Glutamine (Correct answer)
- Glycine
- Serine
Correct answer: Glutamine
Glutamine becomes conditionally essential during critical illness as it is rapidly depleted; it fuels enterocytes, lymphocytes, and macrophages and helps maintain gut barrier integrity.
Question 5: In Wilson's disease, which mineral accumulates pathologically in the liver, brain, and cornea due to impaired biliary excretion?
- Iron
- Zinc
- Copper (Correct answer)
- Manganese
Correct answer: Copper
Wilson's disease results from mutations in ATP7B, impairing hepatic copper export into bile and causing toxic copper accumulation in the liver, basal ganglia, and cornea (Kayser-Fleischer rings).
Question 6: A critically ill ICU patient on enteral nutrition develops diarrhea, hyponatremia, and muscle cramps. Serum levels reveal the likely cause. Which electrolyte is most likely depleted?
- Magnesium (Correct answer)
- Potassium
- Zinc
- Selenium
Correct answer: Magnesium
Hypomagnesemia in ICU patients causes refractory hypokalemia and hyponatremia, muscle cramps, and arrhythmias, and is common with diarrhea-associated losses.
Question 7: Which enzyme is the rate-limiting step in de novo fatty acid synthesis and is allosterically activated by citrate?
- Fatty acid synthase (FAS)
- Acetyl-CoA carboxylase (ACC) (Correct answer)
- HMG-CoA reductase
- ATP-citrate lyase
Correct answer: Acetyl-CoA carboxylase (ACC)
Acetyl-CoA carboxylase (ACC) is the rate-limiting enzyme of fatty acid synthesis; citrate signals energy abundance and activates ACC to convert acetyl-CoA to malonyl-CoA.
BCSE BCSE - Basic and Clinical Sciences Examination Clinical Nutrition and Metabolism Questions and Answers 5
Which lipoprotein particle is primarily responsible for reverse cholesterol transport from peripheral tissues to the liver?