FMGE Biochemistry questions with answers

1. Q1. Phase II hepatic metabolism renders lipophilic drugs water-soluble for excretion. Which conjugation reaction handles the greatest share of this load, catalysed by UDP-glucuronosyltransferase?

   • A. Sulfation
   • B. Acetylation
   • C. Glutathione conjugation
   • D. Glucuronidation

   Answer: D. Glucuronidation

2. Q2. A child of short stature has sun-sensitive facial erythema, recurrent infections and cultured cells showing a striking increase in sister chromatid exchange. A defect in which class of enzyme underlies this disorder?

   • A. Nucleotide excision repair endonuclease
   • B. DNA helicase
   • C. Mismatch repair protein
   • D. DNA polymerase III

   Answer: B. DNA helicase

1. Q1. A neonate has profound hypotonia, a high forehead, hepatomegaly and markedly raised plasma very-long-chain fatty acids. Failure of which organelle explains the biochemical finding?

   • A. Lysosome
   • B. Smooth endoplasmic reticulum
   • C. Peroxisome
   • D. Golgi apparatus

   Answer: C. Peroxisome

2. Q2. A breastfed neonate develops vomiting, jaundice, hepatomegaly and bilateral cataracts in the first weeks of life. Urine is positive for a reducing substance but negative on a glucose oxidase strip. Which enzyme is deficient?

   • A. Galactokinase
   • B. UDP-galactose-4-epimerase
   • C. Galactose-1-phosphate uridyltransferase
   • D. Fructose-1-phosphate aldolase

   Answer: C. Galactose-1-phosphate uridyltransferase

1. Q1. A child has white hair, very pale skin and nystagmus from birth, with a normal plasma phenylalanine. The defect lies in the enzyme that converts tyrosine to DOPA. Which enzyme, and what is the condition?

   • A. Phenylalanine hydroxylase, causing phenylketonuria
   • B. Homogentisate oxidase, causing alkaptonuria
   • C. Tyrosinase, causing oculocutaneous albinism
   • D. Dopamine beta-hydroxylase, causing orthostatic hypotension

   Answer: C. Tyrosinase, causing oculocutaneous albinism

2. Q2. A mature erythrocyte has no mitochondria yet still generates ATP. Which pathway allows this, and where does it run?

   • A. The citric acid cycle, in the cytosol
   • B. Glycolysis, entirely in the cytosol
   • C. Beta oxidation, in the cytosol
   • D. Oxidative phosphorylation, on the plasma membrane

   Answer: B. Glycolysis, entirely in the cytosol

1. Q1. A man whose diet has been almost entirely maize for months has diarrhoea, a symmetrical pigmented dermatitis on sun-exposed skin, and memory impairment. Why does a maize-based diet cause this?

   • A. Maize protein is deficient in lysine, impairing collagen synthesis
   • B. Maize niacin is bound as niacytin and its tryptophan content is low, so niacin cannot be made
   • C. Maize phytate binds zinc, preventing its absorption
   • D. Maize contains an antivitamin that destroys thiamine

   Answer: B. Maize niacin is bound as niacytin and its tryptophan content is low, so niacin cannot be made

2. Q2. For an enzyme obeying Michaelis-Menten kinetics, what does Km tell you, and how is it affected by substrate concentration?

   • A. Km is the substrate concentration at half maximal velocity, and is independent of substrate concentration
   • B. Km rises in direct proportion to substrate concentration
   • C. Km is the maximal velocity divided by enzyme concentration
   • D. Km falls as substrate concentration rises

   Answer: A. Km is the substrate concentration at half maximal velocity, and is independent of substrate concentration

1. Q1. Which organelle contains the acid hydrolases and myeloperoxidase system that digest phagocytosed bacteria, and at what pH does it work?

   • A. Peroxisome, at neutral pH
   • B. Mitochondrion, at alkaline pH
   • C. Lysosome, at acid pH maintained by a proton pump
   • D. Golgi apparatus, at neutral pH

   Answer: C. Lysosome, at acid pH maintained by a proton pump

2. Q2. Cholesterol synthesis begins in the cytosol from a two-carbon precursor. What is that precursor, and which enzyme catalyses the rate-limiting step?

   • A. Malonyl CoA, with acetyl CoA carboxylase
   • B. Oxaloacetate, with citrate synthase
   • C. Propionyl CoA, with methylmalonyl mutase
   • D. Acetyl CoA, with HMG-CoA reductase

   Answer: D. Acetyl CoA, with HMG-CoA reductase

1. Q1. A cell is disrupted and its contents separated by differential centrifugation. In which fraction will lactate dehydrogenase be found, and why?

   • A. The mitochondrial fraction, because it feeds the electron transport chain
   • B. The lysosomal fraction, because it is an acid hydrolase
   • C. The nuclear fraction, because it binds chromatin
   • D. The cytosolic fraction, because it catalyses the final step of glycolysis

   Answer: D. The cytosolic fraction, because it catalyses the final step of glycolysis

2. Q2. A man on haemodialysis for fifteen years develops carpal tunnel syndrome and shoulder pain from amyloid deposits. Which protein forms the fibrils, and why does it accumulate?

   • A. AL amyloid, from monoclonal light chains
   • B. AA amyloid, from chronic inflammation
   • C. Transthyretin, from an inherited mutation
   • D. Beta-2 microglobulin, because it is not cleared by conventional dialysis membranes

   Answer: D. Beta-2 microglobulin, because it is not cleared by conventional dialysis membranes

1. Q1. Which of the following enzymes does NOT contain copper at its active site?

   • A. Manganese superoxide dismutase
   • B. Tyrosinase
   • C. Lysyl oxidase
   • D. Cytochrome c oxidase

   Answer: A. Manganese superoxide dismutase

2. Q2. Nitric oxide is generated by nitric oxide synthase. Which amino acid is the substrate, and what is the co-product?

   • A. Glycine, producing serine
   • B. Lysine, producing carnitine
   • C. Arginine, producing citrulline
   • D. Methionine, producing homocysteine

   Answer: C. Arginine, producing citrulline

1. Q1. Carbonic anhydrase catalyses the hydration of carbon dioxide. Which trace element is essential at its active site?

   • A. Iron
   • B. Calcium
   • C. Potassium
   • D. Zinc

   Answer: D. Zinc

2. Q2. Which hormone suppresses gluconeogenesis, and by which key mechanism?

   • A. Glucagon, by raising cyclic AMP
   • B. Cortisol, by inducing gluconeogenic enzymes
   • C. Insulin, by reducing transcription of PEP carboxykinase and lowering fructose-2,6-bisphosphate turnover in favour of glycolysis
   • D. Adrenaline, by mobilising glycogen

   Answer: C. Insulin, by reducing transcription of PEP carboxykinase and lowering fructose-2,6-bisphosphate turnover in favour of glycolysis

1. Q1. Fluoride in a grey-top blood tube preserves glucose by inhibiting glycolysis. Which enzyme does it inhibit?

   • A. Hexokinase
   • B. Phosphofructokinase-1
   • C. Pyruvate kinase
   • D. Enolase

   Answer: D. Enolase

2. Q2. Maple syrup urine disease results from failure to decarboxylate the keto acids of which amino acids, and which enzyme complex is defective?

   • A. Aromatic amino acids, with phenylalanine hydroxylase
   • B. Sulphur-containing amino acids, with cystathionine synthase
   • C. Basic amino acids, with ornithine transcarbamylase
   • D. Branched-chain amino acids, with branched-chain alpha-keto acid dehydrogenase

   Answer: D. Branched-chain amino acids, with branched-chain alpha-keto acid dehydrogenase

1. Q1. The urea cycle spans two cellular compartments. Which steps occur where?

   • A. Entirely within mitochondria
   • B. Entirely within cytosol
   • C. The first two steps in mitochondria and the remainder in cytosol
   • D. The first two in cytosol and the remainder in mitochondria

   Answer: C. The first two steps in mitochondria and the remainder in cytosol

2. Q2. Which codon initiates translation, and which amino acid does it specify in eukaryotes?

   • A. UAA, specifying no amino acid
   • B. UGA, specifying selenocysteine
   • C. AUG, specifying methionine
   • D. UAG, specifying glutamine

   Answer: C. AUG, specifying methionine

Every FMGE session paper, all 19 subjects together, is on our previous year questions page.