functions of bile salts
TRANSCRIPT
Functions of Bile Salts
Ayesha Akhtar
Liver• Location
• R. Hypochondrium• Epigastric region
• 4 Lobes• Left • Quadrate• Caudate• Right
• Each lobe has lobules – Contains hepatocytes – Surround sinusoids – Feed into central vein
What is Bile?
What is Bile?
Bile is • Dark green to yellowish brown viscous fluid • Secreted by Liver parenchymal cells (Hepatocytes)• Through bile Canaliculi (network of space between
Hepatocytes) and bile duct and • is stored in gallbladder • 500-1000ml (approx) of bile is secreted per day by liver
Composition of Bile
It contains• 97% water• 3% solids (75% of it is organic matter & rest is
inorganic salts)
Organic matter consist of,• Bile salts• Mucin• Bile pigments• Lipids( including fats, fatty acids, phospholipids
& cholesterol)
Inorganic part consist of Ions of Na, K, HCO3, Cl
Bile acids from cholesterol
• formed from cholesterol in the liver
• stored in the gall bladder in bile as bile salts (sodium and potassium)
• utilized during digestion of fats and other lipid substances (act as detergents)
CholateCholateCholateCholateCholesterolCholesterolCholesterolCholesterol
CholesterolCholesterol77-hydroxylase-hydroxylase
CholesterolCholesterol77-hydroxylase-hydroxylase
Cholate & Chenodeoxycholate are primary bile salts
Approximate composition of bile salts• Glycocholate – 24%• Glycochenodeoxycholate – 24%• Taurocholate – 12%• Taurochenodeoxycholate – 12%• Glycodeoxycholate -- 16%• Taurodeoxycholate – 8%• Various lithocholate – 4%
Properties of Bile salts
• detergent character of bile salts is due to the hydrophobic-hydrophilic nature of the molecules
• the presence of hydroxyl (or sulfate) and the terminal carboxyl group on the tail gives the molecule its hydrophilic face
• the steroid ring provides the hydrophobic face
• 3-4 grams present in blood which undergoes enterohepatic circulation 6-8 times/day
Function of bile salts
Emulsification of fats due to detergent activity Decreasing surface tension Emulsify fats, which is a prerequisite for the action of
pancreatic lipase Accelerating the action of pancreatic lipase Aid in the absorption of fat-soluble vitamins that
include, Keep cholesterol in solution (as micelles) Choleretic action Solubility of cholesterol Antiseptic effect
Function of bile salts
Emulsification of fats due to detergent activity Accelerating the action of pancreatic lipase In the presence of bile salts, Colipase binds to lipase, shifting pH pf enzyme from 9.0 to 6.0 Aid in the absorption of fat-soluble vitamins that
include,
Keep cholesterol in solution (as micelles) Choleretic action Solubility of cholesterol Antiseptic effect
Function of bile salts
Emulsification of fats due to detergent activity Accelerating the action of pancreatic lipase Aid in the absorption of fat-soluble vitamins that
include, Vitamin A, D, E and K Its also absorb carotene Keep cholesterol in solution (as micelles) Choleretic action Solubility of cholesterol Antiseptic effect
Function of bile salts
Emulsification of fats due to detergent activity Accelerating the action of pancreatic lipase Aid in the absorption of fat-soluble vitamins that
include, Keep cholesterol in solution (as micelles) forms ‘micelles’ with fatty acid, mono & diacyl glycerol &
also TG making them water soluble and helps it in absorption
Choleretic action Solubility of cholesterol Antiseptic effect
Function of bile salts
Emulsification of fats due to detergent activity Accelerating the action of pancreatic lipase Aid in the absorption of fat-soluble vitamins that
include, Keep cholesterol in solution (as micelles) Intestinal motility Choleretic action stimulate liver to secrete more bile salts Solubility of cholesterol Antiseptic effect
Function of bile salts
Emulsification of fats due to detergent activity Accelerating the action of pancreatic lipase Aid in the absorption of fat-soluble vitamins that
include, Keep cholesterol in solution (as micelles) Intestinal motility Choleretic action Solubility of cholesterol Keep cholesterol in solution
Function of bile salts
Emulsification of fats due to detergent activity Accelerating the action of pancreatic lipase Aid in the absorption of fat-soluble vitamins that
include, Keep cholesterol in solution (as micelles) Intestinal motility Choleretic action Solubility of cholesterol Antiseptic effect
CholesterolCholesterolCholesterolCholesterol
Bile SaltBile SaltBile SaltBile Salt
PhospholipidPhospholipidPhospholipidPhospholipid
Structure of Biliary and Intestinal Structure of Biliary and Intestinal MicellesMicelles
Functions of Micelles
• Transport cholesterol from the liver into the intestine via the biliary tree
• Participate in fat digestion and absorption
Biliary Lipid Secretion
Sinusoidal Membrane
BloodBloodBloodBlood HepatocyteHepatocyteHepatocyteHepatocyte
Canalicular Membrane
Bile SaltBile SaltBile SaltBile Salt
ABCG5/G8Cholesterol
ABCB4Phospholipid
ABCB11
BileBileBileBile
Clinical Aspects
• Liver test Bile salts are greatly increased in obstructive jaundice and are used
as diagnostic tests for it
• GallstonesIn the absence of bile salts, cholesterol may be precipitated as
‘Gallstones’
References
1. Essentials of Biochemistry
by Mushtaq Ahmad
2. Textbook of Medical Biochemistry
by MN Chatterjea & Rana Shinde