Deamination MCQs With Answer is an essential revision resource for B. Pharm students preparing for biochemistry and pharmacology exams. This focused introduction covers biochemical deamination mechanisms, oxidative and non‑oxidative pathways, key enzymes (glutamate dehydrogenase, aminotransferases, monoamine oxidase), coenzymes (PLP, NAD+/NADP+, FAD), ammonia detoxification, and clinical implications such as hyperammonemia and drug interactions. Practicing targeted multiple‑choice questions helps consolidate understanding of amino acid catabolism, urea cycle regulation, and drug‑related deamination. Clear explanations support problem solving and exam readiness. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is deamination in biochemical terms?
- Removal of an amino group from an amino acid to form ammonia
- Addition of an amino group to a keto acid
- Conversion of ammonia to urea
- Transfer of an amino group between two amino acids
Correct Answer: Removal of an amino group from an amino acid to form ammonia
Q2. Which organ is the principal site for amino acid deamination and urea synthesis?
- Kidney cortex
- Liver hepatocytes
- Pancreas
- Skeletal muscle
Correct Answer: Liver hepatocytes
Q3. Which enzyme catalyzes the oxidative deamination of glutamate?
- Glutamate dehydrogenase (GDH)
- Alanine aminotransferase (ALT)
- Glutaminase
- Carbamoyl phosphate synthetase I
Correct Answer: Glutamate dehydrogenase (GDH)
Q4. Which coenzymes can act as electron acceptors for glutamate dehydrogenase?
- NAD+ or NADP+
- FAD only
- CoA
- Biotin
Correct Answer: NAD+ or NADP+
Q5. Which cofactor is essential for transamination reactions?
- Pyridoxal phosphate (PLP)
- Thiamine pyrophosphate (TPP)
- Biotin
- Nicotinamide adenine dinucleotide (NAD+)
Correct Answer: Pyridoxal phosphate (PLP)
Q6. Which amino acid is the most common substrate for oxidative deamination in mammals?
- Glutamate
- Lysine
- Phenylalanine
- Tryptophan
Correct Answer: Glutamate
Q7. Oxidative deamination of glutamate yields which products?
- Alpha‑ketoglutarate and ammonia
- Pyruvate and ammonia
- Ornithine and urea
- Citrate and CO2
Correct Answer: Alpha‑ketoglutarate and ammonia
Q8. Where does the urea cycle primarily occur within the cell?
- Lysosome
- Mitochondria and cytosol of hepatocytes
- Sarcoplasmic reticulum
- Peroxisome
Correct Answer: Mitochondria and cytosol of hepatocytes
Q9. Which enzyme catalyzes the formation of carbamoyl phosphate in the urea cycle?
- Carbamoyl phosphate synthetase I (CPS I)
- Ornithine transcarbamylase
- Arginase
- Argininosuccinate lyase
Correct Answer: Carbamoyl phosphate synthetase I (CPS I)
Q10. What is the obligatory allosteric activator of CPS I?
- N‑acetylglutamate
- ATP
- Glutamine
- Carbamoyl phosphate
Correct Answer: N‑acetylglutamate
Q11. Which amino acid functions as the major nitrogen carrier from muscle to the liver?
- Alanine
- Glycine
- Taurine
- Leucine
Correct Answer: Alanine
Q12. Which enzyme incorporates free ammonia into glutamate to form glutamine?
- Glutamine synthetase
- Glutaminase
- Glutamate dehydrogenase
- Aminotransferase
Correct Answer: Glutamine synthetase
Q13. Which enzyme releases ammonia from glutamine in the liver and kidney?
- Glutaminase
- Glutamine synthetase
- Glutamate dehydrogenase
- Carbamoyl phosphate synthetase II
Correct Answer: Glutaminase
Q14. How does transamination differ from oxidative deamination?
- Transamination transfers the amino group to a keto acid; oxidative deamination releases free ammonia
- Transamination releases ammonia; oxidative deamination transfers amino groups to pyruvate
- Both processes produce urea directly
- Transamination occurs only in mitochondria while oxidative deamination is cytosolic
Correct Answer: Transamination transfers the amino group to a keto acid; oxidative deamination releases free ammonia
Q15. Deamination of alanine yields which gluconeogenic substrate?
- Pyruvate
- Oxaloacetate
- Acetyl‑CoA
- Succinyl‑CoA
Correct Answer: Pyruvate
Q16. Enzymes that catalyze amino group transfers are called:
- Aminotransferases (transaminases)
- Dehydrogenases
- Hydrolases
- Ligases
Correct Answer: Aminotransferases (transaminases)
Q17. A cardinal clinical feature of hyperammonemia is:
- Neurological symptoms and encephalopathy
- Hypertension
- Hypoglycemia without neurological signs
- Muscle hypertrophy
Correct Answer: Neurological symptoms and encephalopathy
Q18. Which inherited urea cycle defect is most commonly X‑linked and causes hyperammonemia?
- Ornithine transcarbamylase (OTC) deficiency
- Arginase deficiency
- Carbamoyl phosphate synthetase II deficiency
- Phenylketonuria
Correct Answer: Ornithine transcarbamylase (OTC) deficiency
Q19. Which anticonvulsant drug is well known to cause hyperammonemia by interfering with nitrogen metabolism?
- Valproic acid
- Phenytoin
- Carbamazepine
- Lamotrigine
Correct Answer: Valproic acid
Q20. Spontaneous deamination of cytosine in DNA converts it to which base?
- Uracil
- Thymine
- Adenine
- Guanine
Correct Answer: Uracil
Q21. Deamination of 5‑methylcytosine leads to which consequence in DNA?
- Formation of thymine and potential C→T mutation
- Formation of uracil that is immediately corrected
- Conversion to adenine
- No change to the base sequence
Correct Answer: Formation of thymine and potential C→T mutation
Q22. Which DNA repair enzyme excises uracil resulting from cytosine deamination?
- Uracil‑DNA glycosylase (UDG)
- DNA ligase
- Topoisomerase I
- RNA polymerase
Correct Answer: Uracil‑DNA glycosylase (UDG)
Q23. Which enzyme family performs oxidative deamination of monoamine neurotransmitters?
- Monoamine oxidases (MAO)
- Cytochrome P450 enzymes
- Acetylcholinesterases
- Glutathione S‑transferases
Correct Answer: Monoamine oxidases (MAO)
Q24. Inhibition of MAO results in increased levels of which compounds?
- Monoamine neurotransmitters such as serotonin, norepinephrine, and dopamine
- Urea and ammonia
- Fatty acids in plasma
- Insulin secretion
Correct Answer: Monoamine neurotransmitters such as serotonin, norepinephrine, and dopamine
Q25. Monoamine oxidase acting on dopamine initially produces which aldehyde intermediate?
- 3,4‑Dihydroxyphenylacetaldehyde (DOPAL)
- Homogentisic aldehyde
- Vanillylmandelic aldehyde
- Acetaldehyde
Correct Answer: 3,4‑Dihydroxyphenylacetaldehyde (DOPAL)
Q26. Which prosthetic group is associated with MAO activity?
- FAD (flavin adenine dinucleotide)
- PLP (pyridoxal phosphate)
- Biotin
- Heme
Correct Answer: FAD (flavin adenine dinucleotide)
Q27. Which amino acid is the main substrate for renal ammoniagenesis used in acid excretion?
- Glutamine
- Tryptophan
- Phenylalanine
- Histidine
Correct Answer: Glutamine
Q28. Nitrous acid can cause deamination of nucleotide bases; this process is called:
- Nitrosative deamination
- Oxidative phosphorylation
- Transamination
- Hydrolytic methylation
Correct Answer: Nitrosative deamination
Q29. How many high‑energy phosphate bonds are consumed per molecule of urea synthesized in the urea cycle?
- 4 high‑energy phosphate bonds
- 1 high‑energy phosphate bond
- 2 high‑energy phosphate bonds
- 0 high‑energy phosphate bonds
Correct Answer: 4 high‑energy phosphate bonds
Q30. Which reaction is reversible and links amino acid and TCA metabolism during deamination and amination?
- Glutamate dehydrogenase catalyzed reaction
- Carbamoyl phosphate synthetase I reaction
- Arginase reaction
- Glutaminase reaction
Correct Answer: Glutamate dehydrogenase catalyzed reaction
Q31. D‑Amino acid oxidase primarily deaminates which type of substrates?
- D‑amino acids such as D‑serine
- L‑amino acids only
- Peptides larger than 10 residues
- Fatty acids
Correct Answer: D‑amino acids such as D‑serine
Q32. PLP forms a Schiff base with which amino acid residue in aminotransferase active sites?
- Lysine residue
- Serine residue
- Cysteine residue
- Histidine residue
Correct Answer: Lysine residue
Q33. Which organ exhibits high glutaminase activity facilitating ammonia release for urea synthesis?
- Kidney proximal tubule and liver
- Adipose tissue
- Cardiac muscle only
- Red blood cells
Correct Answer: Kidney proximal tubule and liver
Q34. What is the major nontoxic transporter of ammonia in blood?
- Glutamine
- Urea
- Ammonium ion (NH4+) free
- Carbamoyl phosphate
Correct Answer: Glutamine
Q35. In hepatic encephalopathy, accumulation of which compounds in brain cells contributes to swelling and dysfunction?
- Ammonia and glutamine
- Urea and ornithine
- Glucose and lactate
- Acetoacetate and beta‑hydroxybutyrate
Correct Answer: Ammonia and glutamine
Q36. Which enzyme catalyzes the condensation of ornithine with carbamoyl phosphate to form citrulline?
- Ornithine transcarbamylase
- Arginase
- Citrulline synthase
- Argininosuccinate lyase
Correct Answer: Ornithine transcarbamylase
Q37. Which urea cycle steps occur inside the mitochondrial matrix?
- Carbamoyl phosphate formation and citrulline synthesis
- Argininosuccinate cleavage and urea formation
- Arginine synthesis only
- All steps are cytosolic
Correct Answer: Carbamoyl phosphate formation and citrulline synthesis
Q38. A negative nitrogen balance indicates which physiological state?
- Net protein breakdown exceeding synthesis (catabolism)
- Net protein synthesis exceeding breakdown (anabolism)
- Normal balanced state
- Excessive dietary protein intake
Correct Answer: Net protein breakdown exceeding synthesis (catabolism)
Q39. Which irreversible MAO inhibitor used in psychiatry can affect deamination of monoamines?
- Phenelzine
- Fluoxetine
- Buspirone
- Haloperidol
Correct Answer: Phenelzine
Q40. Deamination of which amino acid yields oxaloacetate, a glucogenic TCA intermediate?
- Aspartate
- Leucine
- Lysine
- Phenylalanine
Correct Answer: Aspartate
Q41. Which enzyme catalyzes serine deamination to pyruvate and ammonia?
- Serine dehydratase (serine deaminase)
- Serine transaminase
- Serine hydroxymethyltransferase
- Serine racemase
Correct Answer: Serine dehydratase (serine deaminase)
Q42. Which amino acid is strictly ketogenic and its catabolism yields acetoacetate or acetyl‑CoA?
- Leucine
- Alanine
- Glutamate
- Valine
Correct Answer: Leucine
Q43. Which cofactor is also required by serine dehydratase for catalysis?
- Pyridoxal phosphate (PLP)
- Biotin
- FAD
- NADH
Correct Answer: Pyridoxal phosphate (PLP)
Q44. Which enzyme deaminates adenosine to inosine in purine metabolism?
- Adenosine deaminase (ADA)
- Adenine phosphoribosyltransferase
- Xanthine oxidase
- Purine nucleoside phosphorylase
Correct Answer: Adenosine deaminase (ADA)
Q45. Deficiency of adenosine deaminase (ADA) classically causes which immunological disorder?
- Severe combined immunodeficiency (SCID)
- Chronic granulomatous disease
- Systemic lupus erythematosus
- DiGeorge syndrome
Correct Answer: Severe combined immunodeficiency (SCID)
Q46. Incorporation of free ammonia into alpha‑ketoglutarate to form glutamate is called what?
- Reductive amination by glutamate dehydrogenase
- Oxidative phosphorylation
- Transamination
- Beta‑oxidation
Correct Answer: Reductive amination by glutamate dehydrogenase
Q47. Monoamine oxidase is localized primarily to which cellular structure?
- Mitochondrial outer membrane
- Nuclear envelope
- Smooth endoplasmic reticulum
- Golgi apparatus
Correct Answer: Mitochondrial outer membrane
Q48. Deamination of serine produces which metabolites relevant to energy metabolism?
- Pyruvate and ammonia
- Oxaloacetate and urea
- Acetyl‑CoA and CO2
- Alpha‑ketoglutarate and glutamine
Correct Answer: Pyruvate and ammonia
Q49. Which serum enzymes are aminotransferases that reflect hepatic transamination activity rather than deamination?
- Alanine aminotransferase (ALT) and aspartate aminotransferase (AST)
- Lactate dehydrogenase and creatine kinase
- Alkaline phosphatase and amylase
- Monoamine oxidase and adenosine deaminase
Correct Answer: Alanine aminotransferase (ALT) and aspartate aminotransferase (AST)
Q50. Rapid laboratory measurement of plasma ammonia for suspected deamination disorders commonly uses which enzymatic assay?
- Glutamate dehydrogenase‑based enzymatic assay
- Hexokinase glucose assay
- Total bilirubin assay
- Creatinine clearance test
Correct Answer: Glutamate dehydrogenase‑based enzymatic assay
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