Bile acid

A cholesterol-derived molecule produced by the liver that aids fat digestion by emulsifying dietary lipids and enabling their absorption.

Bile salt: An ionized bile acid paired with a positively charged ion, such as sodium or potassium. Bile acids commonly act in the intestine in this ionized, water-soluble form.
Cholesterol: A sterol lipid found in animal cell membranes and used to synthesize steroid hormones, vitamin D, and bile acids. The liver converts cholesterol into the bile acid family.
CYP7A1: A liver enzyme that catalyzes the rate-limiting step in the classic pathway of bile acid synthesis from cholesterol. It initiates the principal route by which the liver makes bile acids.
Bile acid sequestrant: A medicine that binds bile acids in the intestine and reduces their reabsorption. These drugs interrupt recycling and can lower blood LDL cholesterol.
Micelle: A small aggregate of amphipathic molecules that presents a water-compatible exterior around a hydrophobic interior. Bile acids assemble mixed micelles that carry lipid digestion products through intestinal fluid.
Amphipathic molecule: A molecule with distinct hydrophilic and hydrophobic regions. Bile acids' contrasting molecular faces let them interact with both water and dietary lipids.
Cholic acid: A primary bile acid synthesized in the liver from cholesterol. It is one of the two major primary bile acids in humans.
Ursodeoxycholic acid: A hydrophilic bile acid used to treat selected cholestatic liver diseases and some cholesterol gallstones. It is a therapeutic bile acid with effects distinct from the major endogenous species.
Enterohepatic circulation: The circulation of substances from the liver into the intestine and back to the liver through portal blood. Most bile acids return from the intestine to the liver for reuse.
Emulsification: The dispersal of one liquid into small droplets within another liquid that does not mix with it. Bile acids stabilize small fat droplets, increasing the surface available to digestive enzymes.

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