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1.2 Catecholamine (Amine) Hormone Synthesis — Test 1
Q1. Catecholamines (dopamine, norepinephrine, epinephrine) are all derived from the amino acid:✓ Tyrosine
Q2. The rate-limiting enzyme of catecholamine biosynthesis is:✓ Tyrosine hydroxylase
Q3. Conversion of DOPA to dopamine is catalysed by aromatic amino-acid (DOPA) decarboxylase, which requires the cofactor:✓ Pyridoxal phosphate (vitamin B6)
Q4. Dopamine is converted to norepinephrine by dopamine beta-hydroxylase, which contains copper and requires:✓ Ascorbate (vitamin C)
Q5. The methylation of norepinephrine to epinephrine is carried out by PNMT, using which methyl donor?✓ S-adenosylmethionine (SAM)
Q6. Methylation of norepinephrine to epinephrine occurs predominantly in the:✓ Adrenal medulla
Q7. The enzyme PNMT is induced by:✓ Glucocorticoids (cortisol)
Q8. Consider the catecholamine pathway. Which combination of statements is correct?✓ B and D
Q9. The cofactor required by tyrosine hydroxylase is:✓ Tetrahydrobiopterin (BH4)
Q10. Catecholamines are inactivated mainly by the enzymes:✓ Monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT)
Q11. Chromaffin cells of the adrenal medulla are embryologically derived from the:✓ Neural crest
Q12. Unlike steroid and thyroid hormones, catecholamines exert their effects mainly by:✓ Binding cell-surface receptors and using second messengers
Q13. Match each enzyme with the reaction it catalyses and choose the correct option.✓ A-ii, B-iii, C-i
Q14. A phaeochromocytoma is a secondary cause of hypertension because it over-secretes:✓ Catecholamines (epinephrine / norepinephrine)
Q15. Within the adrenal medulla, synthesized catecholamines are stored in:✓ Chromaffin (secretory) granules
Q16. Tyrosine, the precursor of catecholamines, is itself formed from phenylalanine by:✓ Phenylalanine hydroxylase
Q17. Which catecholamine is the major secretory product of the human adrenal medulla?✓ Epinephrine
Q18. Reduced synthesis of S-adenosylmethionine (e.g. in B12/folate deficiency) can impair which conversion?✓ Norepinephrine -> Epinephrine
Q19. The hydroxylation that converts dopamine to norepinephrine occurs:✓ Inside the storage vesicle (DBH is vesicular)
Q20. Which statement about catecholamine action is correct?✓ beta-adrenergic receptors act via cAMP, while alpha1 receptors act via IP3/Ca2+