Precursor of Cholesterol

The precursor of cholesterol is-

Correct Answer: Acetyl CoA

Acetyl-CoA is the universal precursor of cholesterol. All 27 carbon atoms of cholesterol are derived from Acetyl-CoA through the mevalonate pathway.

Cholesterol Biosynthesis Pathway

• 3 Acetyl-CoA → HMG-CoA (hydroxymethylglutaryl-CoA)
• HMG-CoA → Mevalonate (rate-limiting step; enzyme: HMG-CoA reductase)
• Mevalonate → Squalene → Lanosterol → Cholesterol
• Statins (e.g., atorvastatin, simvastatin) inhibit HMG-CoA reductase → lower cholesterol synthesis

Cholesterol's Important Roles

• Structural component of all cell membranes (maintains fluidity)
• Precursor of: all steroid hormones (testosterone, estrogen, progesterone, cortisol, aldosterone)
• Precursor of: Vitamin D (cholecalciferol)
• Precursor of: Bile acids (for fat digestion)

Other Precursors Summary

• Acetyl-CoA → Cholesterol → Steroid hormones + Vitamin D
• Arachidonic acid → Prostaglandins
• Tyrosine → Thyroxin + Catecholamines
• Tryptophan → Niacin
• Hexose sugar → Vitamin C
• Propionate → Glucose (ruminants)