bile

Biochemistry

• Composition:
  • bile salts
    • cholic acid & chenodeoxycholic acid (major bile acid)
    • in a 1st step, bile acids are converted to an acyl-CoA thioester, either in peroxisomes (primary bile acids deriving from the cholesterol pathway), or cytoplasmic at the endoplasmic reticulum (secondary bile acids)
    • in a 2nd step, BAAT catalyzes conjugation of C24 bile acids (choloneates) to glycine & taurine before excretion into bile canaliculi
    • conjugation increases the detergent properties of bile acids in the intestine
    • bile acids are deconjugated by bacteria in the intestine & recycled back to the liver for reconjugation (secondary bile acids)
  • lecithin
  • cholesterol
  • electrolytes
    • Na+: 150 mmol/L
    • K+: 10 mmol/L
    • Cl-: 90 mmol/L
    • HCO3-: 70 mmol/L
• metabolism
  • produced & excreted by liver
    • 0.5-1.0 liters/day
    • 2-3 liters.day
  • concentrated in the gallbladder
  • released into intestines through common bile duct in response to food entering duodenum
  • majority of bile is reabsorbed in ileum
  • returned to liver by way of enterohepatic circulation

More general terms

• extracellular compartment (extracellular space)
• body fluid

Additional terms

• bile acid
• cholesterol
• duodenum
• gallbladder
• ileum
• liver
• phosphatidylcholine (lecithin)