Steroids: Chemistry, stereochemistry and sex hormones, corticoids MCQs With Answer

Steroids: Chemistry, stereochemistry and sex hormones, corticoids MCQs With Answer

Introduction: This quiz set is designed for M.Pharm students studying MPC 104T (Chemistry of Natural Products). It focuses on the steroid nucleus, detailed stereochemistry, biosynthetic pathways from cholesterol, structural differences among sex hormones (androgens, estrogens, progestogens) and corticoids, and structure–activity relationships important in pharmacology. Questions emphasize stereochemical terminology (alpha/beta), ring junctions, key enzymes (CYP11A1, CYP17A1, aromatase), and common synthetic modifications that alter glucocorticoid or mineralocorticoid activity. Use these MCQs to test and deepen your conceptual understanding and to prepare for advanced discussions on steroid chemical biology and therapeutic design.

Q1. Which name correctly describes the core tetracyclic skeleton common to steroid molecules?

• Cyclopentanoperhydrophenanthrene
• Tetracyclohexadecane
• Spirocyclohexanoperhydrobenzene
• Perhydroazulene

Correct Answer: Cyclopentanoperhydrophenanthrene

Q2. How many fused rings compose the steroid nucleus and how are they conventionally labeled?

• Three rings labeled X, Y, Z
• Four fused rings labeled A, B, C, D
• Five fused rings labeled 1–5
• Two fused rings labeled α and β

Correct Answer: Four fused rings labeled A, B, C, D

Q3. In steroid stereochemistry, what does the term “beta (β) substituent” indicate?

• The substituent lies below the mean plane of the ring system
• The substituent lies above the mean plane of the ring system
• The substituent is planar and lies in the ring plane
• The substituent is attached to a sp2 carbon only

Correct Answer: The substituent lies above the mean plane of the ring system

Q4. The designation “5α-H” versus “5β-H” on a steroid refers to the configuration of hydrogen at C-5. Which statement about A/B ring fusion is correct?

• 5α-H corresponds to cis A/B fusion and 5β-H to trans A/B fusion
• 5α-H corresponds to trans A/B fusion and 5β-H to cis A/B fusion
• Both 5α-H and 5β-H always give trans A/B fusion
• 5α-H/5β-H only affect D-ring geometry, not A/B fusion

Correct Answer: 5α-H corresponds to trans A/B fusion and 5β-H to cis A/B fusion

Q5. Which enzyme catalyzes the conversion of cholesterol to pregnenolone, initiating steroidogenesis, and where does it act?

• Aromatase (CYP19A1) in the endoplasmic reticulum
• 17β-Hydroxysteroid dehydrogenase in the cytosol
• Cholesterol side-chain cleavage enzyme (CYP11A1, P450scc) in mitochondria
• 21-Hydroxylase (CYP21A2) in the Golgi apparatus

Correct Answer: Cholesterol side-chain cleavage enzyme (CYP11A1, P450scc) in mitochondria

Q6. Aromatase (CYP19A1) converts which of the following transformations in steroid biosynthesis?

• Progesterone to cortisol by addition of an 11β-hydroxyl
• Testosterone or androstenedione to estradiol or estrone by aromatizing the A-ring
• Cholesterol to pregnenolone by side-chain cleavage
• DHEA to androstenedione by 17β-reduction

Correct Answer: Testosterone or androstenedione to estradiol or estrone by aromatizing the A-ring

Q7. Which functional group is most critical for classical glucocorticoid activity at the receptor?

• 11β-Hydroxyl group on ring C
• 3β-Methyl group on ring A
• 7α-Fluoro group on ring B
• 23-Carboxyl group on the side chain

Correct Answer: 11β-Hydroxyl group on ring C

Q8. Which structural feature is essential for mineralocorticoid (aldosterone-like) activity in corticosteroids?

• Presence of a 21-hydroxyl group
• Introduction of an additional aromatic ring
• Removal of the C17 side chain entirely
• Conversion of the C3-keto to a C3-oxo-enol

Correct Answer: Presence of a 21-hydroxyl group

Q9. Compared to testosterone, which structural changes convert an androgen into an estrogen (e.g., estradiol)?

• Hydrogenation of the A-ring and addition of a C19 methyl
• Aromatization of the A-ring and loss of the C19 methyl group
• Addition of a 21-hydroxyl and oxidation at C11
• Cleavage of the D-ring to form a secosteroid

Correct Answer: Aromatization of the A-ring and loss of the C19 methyl group

Q10. Cortisol and cortisone interconvert via which enzyme system, and what is the key functional difference between them?

• 17β-HSD converts cortisol (11β-OH) to cortisone (11-keto)
• 11β-Hydroxysteroid dehydrogenase interconverts cortisol (11β-OH) and cortisone (11-keto)
• Aromatase converts cortisone to cortisol by aromatizing the A-ring
• 21-Hydroxylase reduces cortisone to cortisol at C21

Correct Answer: 11β-Hydroxysteroid dehydrogenase interconverts cortisol (11β-OH) and cortisone (11-keto)

Q11. Which naturally occurring steroid is the primary progestogen in humans and a direct downstream product of pregnenolone?

• Cortisol
• Progesterone
• Testosterone
• Estradiol

Correct Answer: Progesterone

Q12. Typical structural features that define many active glucocorticoids include which combination?

• Δ4–3-keto structure plus 11β-hydroxyl and 17α-hydroxyl substituents
• Removal of the C3 carbon and formation of a lactone ring at D-ring
• Saturation of the A-ring and absence of hydroxyl groups
• Cleavage of the B-ring to produce a seco-steroid structure

Correct Answer: Δ4–3-keto structure plus 11β-hydroxyl and 17α-hydroxyl substituents

Q13. Steroid hormones typically exert genomic effects by which primary mechanism?

• Binding to membrane-bound ion channels and altering conductance
• Direct enzymatic activation of G-proteins at the cell surface
• Diffusing into cells, binding intracellular receptors, and regulating gene transcription
• Being retained in the extracellular matrix to sequester growth factors

Correct Answer: Diffusing into cells, binding intracellular receptors, and regulating gene transcription

Q14. Which synthetic glucocorticoid is known for high anti-inflammatory potency and very low mineralocorticoid activity?

• Hydrocortisone
• Fludrocortisone
• Dexamethasone
• Aldosterone

Correct Answer: Dexamethasone

Q15. In steroid nomenclature, what does the prefix “alpha (α)” indicate about a substituent’s orientation?

• The substituent is above the plane of the ring system
• The substituent is pointing into the page and not stereochemically defined
• The substituent is below the plane of the ring system
• The substituent is planar and coplanar with the ring

Correct Answer: The substituent is below the plane of the ring system

Q16. Which enzymatic activity of CYP17A1 is responsible for converting 17α-hydroxypregnenolone into dehydroepiandrosterone (DHEA)?

• 17α-hydroxylase only
• 17,20-lyase activity
• Aromatase-type oxygenation
• 21-Hydroxylase action

Correct Answer: 17,20-lyase activity

Q17. For high affinity binding to the estrogen receptor, which two functional groups on estradiol are most important?

• A 3-hydroxyl on the A-ring and a 17β-hydroxyl on the D-ring
• An 11-keto group and a 21-hydroxyl group
• A 9α-fluoro substituent and a 16α-methyl
• A 7-keto group and a 20-carboxyl

Correct Answer: A 3-hydroxyl on the A-ring and a 17β-hydroxyl on the D-ring

Q18. Introduction of a 9α-fluoro substituent into a corticosteroid framework most commonly results in which effect?

• Marked decrease in both glucocorticoid and mineralocorticoid activity
• Increase in glucocorticoid potency and often increased mineralocorticoid activity
• Exclusive increase in estrogenic activity
• Conversion to an inactive metabolite with no receptor binding

Correct Answer: Increase in glucocorticoid potency and often increased mineralocorticoid activity

Q19. The introduction of a Δ1 (1-dehydro) double bond into many corticosteroids has what typical pharmacological effect?

• Reduces glucocorticoid anti-inflammatory potency
• Increases anti-inflammatory potency and metabolic stability
• Eliminates receptor binding completely
• Converts glucocorticoids into mineralocorticoids only

Correct Answer: Increases anti-inflammatory potency and metabolic stability

Q20. Which hydroxyl position on corticosteroids is most commonly esterified to form topical prodrugs and to alter lipophilicity and skin penetration?

• C11-hydroxyl
• C17-hydroxyl
• C21-hydroxyl
• C3-hydroxyl

Correct Answer: C21-hydroxyl

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