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1.4 Steroid Hormone Biosynthesis — Test 1
Q1. All steroid hormones are derived from the common precursor:✓ Cholesterol
Q2. The first and rate-limiting step of steroidogenesis, cholesterol to pregnenolone, is catalysed by cholesterol side-chain cleavage enzyme (P450scc) located in the:✓ Mitochondria
Q3. The conversion of cholesterol to pregnenolone is stimulated by ACTH (in the adrenal). The analogous gonadal stimulus is:✓ LH (luteinizing hormone)
Q4. Steroidogenic acute regulatory protein (StAR) facilitates the transfer of cholesterol into the:✓ Mitochondria
Q5. Which step in steroid biosynthesis, if blocked by inhibiting 17,20-lyase, stops all androgen synthesis but NOT glucocorticoid synthesis?✓ 17-Hydroxypregnenolone -> Dehydroepiandrosterone
Q6. 21-Hydroxylase (CYP21) deficiency, the commonest congenital adrenal hyperplasia, results in:✓ Reduced cortisol and aldosterone with shunting to androgens
Q7. Aromatase (CYP19) catalyses the conversion of:✓ Androgens (e.g. testosterone) to estrogens
Q8. Conversion of testosterone to the more potent androgen dihydrotestosterone in target tissues is catalysed by:✓ 5alpha-reductase
Q9. Regarding the subcellular location of steroidogenic enzymes, which combination is correct?✓ Both A and B are true
Q10. Identify the INCORRECT steroid-synthesis sequence:✓ Pregnenolone -> Estradiol -> Testosterone
Q11. Which of the following is NOT produced by the adrenal cortex?✓ Ponasterone
Q12. Which one of the following is NOT a synthetic steroid?✓ Dehydroepiandrosterone
Q13. In adrenal zonation, aldosterone is produced by the:✓ Zona glomerulosa
Q14. In the adrenal cortex, the major glucocorticoid cortisol is produced by the:✓ Zona fasciculata
Q15. Match each enzyme with its product and choose the correct option.✓ A-ii, B-i, C-iii
Q16. The hormone overproduced in Cushing syndrome (cortisol) is synthesized from which immediate steroid precursor class?✓ Progesterone (21-carbon series)
Q17. 17beta-Estradiol is produced from testosterone by:✓ Aromatization of the A-ring
Q18. A defect in 17alpha-hydroxylase (CYP17) characteristically causes:✓ Decreased cortisol and androgens with mineralocorticoid excess and hypertension
Q19. The ultrastructure typical of an active steroid-secreting cell includes:✓ Abundant smooth ER, lipid droplets and mitochondria with tubular cristae
Q20. Which step in steroid biosynthesis is directly stimulated by ACTH?✓ Cholesterol -> Pregnenolone