Synthesis of adrenaline MCQs With Answer

Synthesis of adrenaline MCQs With Answer is a focused study resource tailored for B. Pharm students aiming to master the biochemical and pharmacological aspects of adrenaline (epinephrine) production. This concise introduction covers enzymatic steps, key cofactors, cellular localization, regulatory signals like cortisol, and clinically relevant inhibitors—essential for exams and practical understanding. Emphasis is placed on tyrosine hydroxylase, DOPA decarboxylase, dopamine β-hydroxylase, and phenylethanolamine N-methyltransferase (PNMT), along with transporters and vesicular storage. Ideal for pharmacology and medicinal chemistry revision, these MCQs reinforce mechanisms, regulation, and therapeutic implications with clear answers and explanations to build strong conceptual knowledge.

Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which enzyme catalyzes the first and rate-limiting step in the biosynthesis of adrenaline?

• Phenylethanolamine N-methyltransferase (PNMT)
• DOPA decarboxylase
• Tyrosine hydroxylase
• Dopamine β-hydroxylase

Correct Answer: Tyrosine hydroxylase

Q2. What is the immediate precursor of dopamine in the catecholamine biosynthetic pathway?

• Tyramine
• L-DOPA (DOPA)
• Norepinephrine
• Homovanillic acid

Correct Answer: L-DOPA (DOPA)

Q3. Which cofactor is required by tyrosine hydroxylase for conversion of tyrosine to DOPA?

• Pyridoxal phosphate (PLP)
• Ascorbic acid (Vitamin C)
• Tetrahydrobiopterin (BH4)
• S-adenosyl methionine (SAM)

Correct Answer: Tetrahydrobiopterin (BH4)

Q4. DOPA decarboxylase requires which vitamin-derived cofactor to convert DOPA to dopamine?

• Vitamin C
• Vitamin B6 (PLP)
• Vitamin B12
• Folate

Correct Answer: Vitamin B6 (PLP)

Q5. Dopamine β-hydroxylase (DBH) converts dopamine to norepinephrine and requires which cofactors?

• BH4 and oxygen
• SAM and magnesium
• Ascorbate (vitamin C) and copper
• PLP and zinc

Correct Answer: Ascorbate (vitamin C) and copper

Q6. Which enzyme methylates norepinephrine to form adrenaline (epinephrine)?

• Catechol-O-methyltransferase (COMT)
• Tyrosine hydroxylase
• Phenylethanolamine N-methyltransferase (PNMT)
• Monoamine oxidase (MAO)

Correct Answer: Phenylethanolamine N-methyltransferase (PNMT)

Q7. What is the methyl donor used by PNMT to convert norepinephrine to epinephrine?

• Folate
• S-adenosyl methionine (SAM)
• Acetyl-CoA
• Biopterin

Correct Answer: S-adenosyl methionine (SAM)

Q8. In the adrenal medulla, PNMT expression is upregulated by which hormone produced in the adrenal cortex?

• Aldosterone
• Cortisol
• Insulin
• Adrenocorticotropic hormone (ACTH)

Correct Answer: Cortisol

Q9. Where is dopamine β-hydroxylase (DBH) primarily localized in chromaffin cells during catecholamine synthesis?

• Cytosol
• Mitochondria
• Vesicular lumen (chromaffin granules)
• Nucleus

Correct Answer: Vesicular lumen (chromaffin granules)

Q10. Which transporter moves catecholamines into storage vesicles in chromaffin cells?

• DAT (dopamine transporter)
• SERT (serotonin transporter)
• VMAT (vesicular monoamine transporter)
• NET (norepinephrine transporter)

Correct Answer: VMAT (vesicular monoamine transporter)

Q11. Which drug inhibits tyrosine hydroxylase and is used experimentally to deplete catecholamines?

• Metyrosine (α-methyl-para-tyrosine)
• Carbidopa
• Reserpine
• Propranolol

Correct Answer: Metyrosine (α-methyl-para-tyrosine)

Q12. Carbidopa inhibits which enzyme, affecting peripheral synthesis of dopamine from DOPA?

• Tyrosine hydroxylase
• DOPA decarboxylase (aromatic L-amino acid decarboxylase)
• Dopamine β-hydroxylase
• Phenylethanolamine N-methyltransferase

Correct Answer: DOPA decarboxylase (aromatic L-amino acid decarboxylase)

Q13. Which physiological signal rapidly increases catecholamine release from the adrenal medulla?

• Parasympathetic activation
• Sympathetic preganglionic stimulation (acetylcholine)
• Thyroid hormone surge
• Antidiuretic hormone (ADH)

Correct Answer: Sympathetic preganglionic stimulation (acetylcholine)

Q14. After synthesis, epinephrine is primarily metabolized by which two enzymes?

• COMT and MAO
• PNMT and DBH
• DOPA decarboxylase and TH
• Acetylcholinesterase and COMT

Correct Answer: COMT and MAO

Q15. Which molecule acts as an essential reducing cofactor for DBH during hydroxylation of dopamine?

• Glutathione
• Ascorbate (vitamin C)
• NADH
• FAD

Correct Answer: Ascorbate (vitamin C)

Q16. The source of carbon and nitrogen for the catechol ring in tyrosine comes from which amino acid?

• Tryptophan
• Phenylalanine
• Glutamate
• Glycine

Correct Answer: Phenylalanine

Q17. In peripheral adrenergic neurons versus adrenal medulla, which enzyme distribution differs significantly affecting epinephrine synthesis?

• Tyrosine hydroxylase
• Phenylethanolamine N-methyltransferase (PNMT)
• DOPA decarboxylase
• Monoamine oxidase

Correct Answer: Phenylethanolamine N-methyltransferase (PNMT)

Q18. Which experimental inhibitor blocks vesicular storage of catecholamines by inhibiting VMAT?

• Reserpine
• Metyrosine
• Carbidopa
• Entacapone

Correct Answer: Reserpine

Q19. Which factor increases PNMT activity in adrenal medulla, promoting epinephrine synthesis?

• High circulating insulin
• High local cortisol levels from adrenal cortex
• High aldosterone levels
• Low ACTH stimulation

Correct Answer: High local cortisol levels from adrenal cortex

Q20. The conversion of norepinephrine to epinephrine by PNMT occurs mainly in which cellular compartment?

• Vesicle lumen
• Cytosol
• Mitochondria
• Golgi apparatus

Correct Answer: Cytosol

Q21. Which of the following is a direct laboratory chemical methylating reagent historically used in synthetic conversion of norepinephrine to epinephrine (in organic synthesis context)?

• Hydrochloric acid
• Methyl iodide
• Sodium borohydride
• Acetic anhydride

Correct Answer: Methyl iodide

Q22. Which genetic or acquired condition would reduce adrenaline production by impairing PNMT induction?

• Adrenal cortical atrophy decreasing cortisol
• Hyperaldosteronism
• Excess thyroid hormone
• Vitamin B6 deficiency

Correct Answer: Adrenal cortical atrophy decreasing cortisol

Q23. Which enzyme deficiency would most directly lower both norepinephrine and epinephrine levels?

• Phenylethanolamine N-methyltransferase deficiency
• Dopamine β-hydroxylase deficiency
• COMT deficiency
• MAO deficiency

Correct Answer: Dopamine β-hydroxylase deficiency

Q24. Which metabolite is the principal urinary end-product of epinephrine metabolism?

• Vanillylmandelic acid (VMA)
• Homovanillic acid (HVA)
• 5-Hydroxyindoleacetic acid (5-HIAA)
• Tyrosine

Correct Answer: Vanillylmandelic acid (VMA)

Q25. Which of the following increases expression of tyrosine hydroxylase via acute phosphorylation-based regulation?

• Neuronal depolarization and calcium influx
• Reduced intracellular calcium
• High glucose levels
• Insulin signaling

Correct Answer: Neuronal depolarization and calcium influx

Q26. Which substrate analog is used clinically to inhibit catecholamine synthesis in pheochromocytoma?

• Carbidopa
• Metyrosine (α-methyl-para-tyrosine)
• Reserpine
• Entacapone

Correct Answer: Metyrosine (α-methyl-para-tyrosine)

Q27. Which enzyme catalyzes methylation of catecholamines at the catechol OH groups during metabolism?

• Catechol-O-methyltransferase (COMT)
• Monoamine oxidase (MAO)
• PNMT
• Tyrosine hydroxylase

Correct Answer: Catechol-O-methyltransferase (COMT)

Q28. Which vitamin deficiency would most likely impair DBH activity and decrease norepinephrine synthesis?

• Vitamin B12 deficiency
• Vitamin C deficiency (scurvy)
• Vitamin D deficiency
• Vitamin A deficiency

Correct Answer: Vitamin C deficiency (scurvy)

Q29. Which statement about adrenomedullary catecholamine synthesis is correct?

• PNMT is located in vesicles and acts before DBH
• DBH converts norepinephrine to dopamine
• Tyrosine is converted to DOPA in the cytosol by TH
• DOPA is converted to norepinephrine directly

Correct Answer: Tyrosine is converted to DOPA in the cytosol by TH

Q30. Which enzyme is membrane-bound and requires molecular oxygen to hydroxylate dopamine to norepinephrine?

• Tyrosine hydroxylase
• DOPA decarboxylase
• Dopamine β-hydroxylase
• Phenylethanolamine N-methyltransferase

Correct Answer: Dopamine β-hydroxylase

Q31. Which change would be expected after chronic stress that elevates ACTH and cortisol?

• Decreased PNMT expression in adrenal medulla
• Increased PNMT expression and higher epinephrine synthesis
• Blockade of TH by cortisol
• Loss of VMAT function

Correct Answer: Increased PNMT expression and higher epinephrine synthesis

Q32. Which laboratory finding indicates increased catecholamine turnover in a patient?

• Low urinary vanillylmandelic acid (VMA)
• Elevated urinary metanephrines and VMA
• High plasma serotonin
• Decreased plasma dopamine

Correct Answer: Elevated urinary metanephrines and VMA

Q33. Which enzyme requires oxygen and tetrahydrobiopterin (BH4) to hydroxylate aromatic amino acids like tyrosine?

• Tyrosine hydroxylase
• DOPA decarboxylase
• Monoamine oxidase
• COMT

Correct Answer: Tyrosine hydroxylase

Q34. Which process is essential for norepinephrine to become available to PNMT for methylation to epinephrine?

• Direct methylation inside vesicles
• Transport of norepinephrine from vesicle to cytosol
• Conversion of norepinephrine to dopamine
• Degradation by MAO first

Correct Answer: Transport of norepinephrine from vesicle to cytosol

Q35. Which pharmacological agent inhibits dopamine β-hydroxylase and can alter catecholamine balance?

• Disulfiram
• Entacapone
• MAO inhibitor selegiline
• Phenylephrine

Correct Answer: Disulfiram

Q36. Which characteristic differentiates epinephrine from norepinephrine chemically?

• Epinephrine has an additional methyl group on the amino nitrogen
• Norepinephrine has an extra methoxy group on the ring
• Epinephrine lacks a catechol ring
• Norepinephrine contains a methyl ester

Correct Answer: Epinephrine has an additional methyl group on the amino nitrogen

Q37. In synthetic organic chemistry, protecting groups for catechol OH are often used because they:

• Reduce reaction yields
• Prevent unwanted oxidation or methylation of the ring
• Increase water solubility only
• Are unnecessary for selective methylation

Correct Answer: Prevent unwanted oxidation or methylation of the ring

Q38. Which of the following best describes the role of SAM in catecholamine metabolism?

• Acts as an oxidizing agent for DBH
• Serves as methyl donor for PNMT and COMT
• Is a vesicular transporter cofactor
• Degrades catecholamines to VMA

Correct Answer: Serves as methyl donor for PNMT and COMT

Q39. Which clinical situation would reduce adrenal epinephrine output acutely?

• Acute sympathetic activation by stress
• Administration of a ganglionic blocker blocking preganglionic firing
• Cortisol surge
• Hypoglycemia

Correct Answer: Administration of a ganglionic blocker blocking preganglionic firing

Q40. Which enzyme activity is most directly measured by urinary metanephrine levels?

• Tyrosine hydroxylase
• PNMT and COMT-mediated metabolism of epinephrine
• DOPA decarboxylase
• DBH activity

Correct Answer: PNMT and COMT-mediated metabolism of epinephrine

Q41. Which amino acid is the immediate precursor to tyrosine in humans and influences catecholamine synthesis?

• Alanine
• Phenylalanine
• Leucine
• Tryptophan

Correct Answer: Phenylalanine

Q42. Which metal ion is essential for dopamine β-hydroxylase catalytic activity?

• Iron (Fe2+)
• Copper (Cu2+)
• Zinc (Zn2+)
• Magnesium (Mg2+)

Correct Answer: Copper (Cu2+)

Q43. Which experimental measure directly reflects tyrosine hydroxylase activity in tissues?

• Rate of conversion of L-DOPA to dopamine
• Rate of conversion of tyrosine to L-DOPA
• Urinary VMA levels
• Plasma epinephrine half-life

Correct Answer: Rate of conversion of tyrosine to L-DOPA

Q44. Which statement is true regarding the stereochemistry of synthetic epinephrine preparations used clinically?

• Only the R-enantiomer is active at adrenergic receptors
• Only the S-enantiomer is active at adrenergic receptors
• Both enantiomers have equal pharmacological potency
• Epinephrine is achiral

Correct Answer: Only the R-enantiomer is active at adrenergic receptors

Q45. Which enzyme deficiency leads to accumulation of dopamine with low norepinephrine and epinephrine, causing autonomic dysfunction?

• COMT deficiency
• Dopamine β-hydroxylase deficiency
• MAO deficiency
• PNMT deficiency

Correct Answer: Dopamine β-hydroxylase deficiency

Q46. In pharmacological blockade of catecholamine synthesis, which combined treatment would most reduce peripheral epinephrine levels?

• PNMT activator plus VMAT inhibitor
• Tyrosine hydroxylase inhibitor (metyrosine) plus DOPA decarboxylase inhibitor (carbidopa)
• COMT inhibitor plus MAO inhibitor
• SAM supplementation plus vitamin C

Correct Answer: Tyrosine hydroxylase inhibitor (metyrosine) plus DOPA decarboxylase inhibitor (carbidopa)

Q47. Which analytical method is commonly used to quantify catecholamines and their metabolites in biological samples?

• Gas chromatography-mass spectrometry (GC-MS) or HPLC with electrochemical detection
• ELISA for hemoglobin
• Western blot for PNMT
• Turbidimetry

Correct Answer: Gas chromatography-mass spectrometry (GC-MS) or HPLC with electrochemical detection

Q48. Which is a direct consequence of inhibiting VMAT in chromaffin cells?

• Increased vesicular storage of catecholamines
• Depletion of vesicular catecholamines and reduced secretion
• Enhanced PNMT activity
• Increased synthesis of tyrosine

Correct Answer: Depletion of vesicular catecholamines and reduced secretion

Q49. In adrenal medulla, why must norepinephrine often exit vesicles to be converted to epinephrine?

• PNMT is located in the cytosol and requires cytosolic access to norepinephrine
• DBH cannot produce norepinephrine inside vesicles
• Norepinephrine is too large to be methylated in vesicles
• Vesicular pH inhibits methylation chemistry

Correct Answer: PNMT is located in the cytosol and requires cytosolic access to norepinephrine

Q50. Which regulatory mechanism provides long-term control of adrenal epinephrine synthesis rather than immediate release?

• Acute depolarization of chromaffin cells
• Post-translational phosphorylation of TH only
• Glucocorticoid-induced upregulation of PNMT gene expression
• Rapid COMT-mediated metabolism

Correct Answer: Glucocorticoid-induced upregulation of PNMT gene expression

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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