Q.32 Match the hormones in Group I with their metabolic precursor in Group II
Group I
- 17-β estradiol
- Thromboxane A2
- Epinephrine
- Retinoic acid
Group II
- Arachidonic acid
- Tyrosine
- β-carotene
- Cholesterol
(A) P-4, Q-2, R-3, S-1
(B) P-1, Q-3, R-2, S-4
(C) P-4, Q-1, R-2, S-3
(D) P-1, Q-2, R-4, S-3
The correct answer to Q.32 is (C) P-4, Q-1, R-2, S-3, correctly matching 17-β estradiol to cholesterol, Thromboxane A2 to arachidonic acid, Epinephrine to tyrosine, and Retinoic acid to β-carotene.
Correct Matching
Group I hormones derive from specific precursors via enzymatic pathways: 17-β estradiol (P) from cholesterol (4) through steroidogenesis; Thromboxane A2 (Q) from arachidonic acid (1) via cyclooxygenase; Epinephrine (R) from tyrosine (2) through catecholamine synthesis; Retinoic acid (S) from β-carotene (3) via cleavage and oxidation.
Biosynthesis Pathways
17-β Estradiol from Cholesterol
Cholesterol serves as the precursor for all steroid hormones, including 17-β estradiol, converted via cytochrome P450 enzymes in the gonads and placenta to yield estrogens critical for reproduction.
Thromboxane A2 from Arachidonic Acid
Arachidonic acid, released from membrane phospholipids, is oxygenated by COX-1 to prostaglandin H2, then isomerized to Thromboxane A2, a platelet aggregator in hemostasis.
Epinephrine from Tyrosine
Tyrosine is hydroxylated to L-DOPA by tyrosine hydroxylase, decarboxylated to dopamine, and further modified to norepinephrine and epinephrine in adrenal medulla.
Retinoic Acid from β-Carotene
β-Carotene, a provitamin A carotenoid, undergoes central cleavage by β-carotene 15,15′-oxygenase to retinal, oxidized to retinoic acid, regulating gene expression via RAR receptors.
Options Breakdown
| Option | P (17-β Estradiol) | Q (Thromboxane A2) | R (Epinephrine) | S (Retinoic Acid) | Correct? |
|---|---|---|---|---|---|
| (A) | 4 (Cholesterol) | 2 (Tyrosine) | 3 (β-carotene) | 1 (Arachidonic) | No |
| (B) | 1 (Arachidonic) | 3 (β-carotene) | 2 (Tyrosine) | 4 (Cholesterol) | No |
| (C) | 4 (Cholesterol) | 1 (Arachidonic) | 2 (Tyrosine) | 3 (β-carotene) | Yes |
| (D) | 1 (Arachidonic) | 2 (Tyrosine) | 4 (Cholesterol) | 3 (β-carotene) | No |
