Topics:
Animal Nutrition, Animal Refresher
Metabolic Precursor of Cholesterol
Precursor of cholesterol is:
- Glucose
- Acetyl CoA — Correct Answer
- Citric acid
- Tryptophan
Explanation:
Correct Answer: Acetyl CoA
All carbon atoms in the complex steroid ring structure of cholesterol originate entirely from Acetyl CoA. The biosynthesis occurs primarily in the liver and involves 3 Acetyl CoA → HMG-CoA → Mevalonate → Squalene → Cholesterol.
Cholesterol Biosynthesis Pathway
| Step | Key Intermediate |
|---|---|
| 3 Acetyl CoA → | HMG-CoA (rate-limiting step) |
| HMG-CoA → | Mevalonate (enzyme: HMG-CoA reductase) |
| Mevalonate → | Squalene (30C) |
| Squalene → | Cholesterol (27C steroid ring) |
Significance of Cholesterol as a Precursor
- Cholesterol → Vitamin D (7-dehydrocholesterol → UV light)
- Cholesterol → All steroid hormones (Testosterone, Estrogen, Progesterone, Cortisol, Aldosterone)
- Cholesterol → Bile acids (for fat digestion)
- Statins (cholesterol-lowering drugs) inhibit HMG-CoA reductase.
Why Other Options Are Wrong
- Glucose → glucose is converted to Acetyl CoA first; the direct precursor is Acetyl CoA, not glucose.
- Citric acid → intermediate of TCA cycle; not a cholesterol precursor.
- Tryptophan → amino acid precursor for Niacin and Serotonin; not cholesterol.
📚 About this Topic — Animal Nutrition
This multiple choice question is from Animal Nutrition, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Nutrition to strengthen your preparation.
