College Answer

Bile is produced by hepatocytes, excretion via cannaliculus and biliary tree. It is stored and 
concentrated in the gallbladder. Bile contains water, bile acids and bile salts, bile pigments and 
electrolytes. Some detail was expected regarding each of these and comment on “Primary bile 
acids”, conjugation with taurine and glycine and production of “bile salts”. It was often not 
appreciated bacteria in gut produce “secondary” bile acids such as deoxycholate and 
lithocholic acid. Additional credit was given for discussing “Unconjugated bilirubin” being 
derived from “heme” component of haemoglobin (85%) is carried via albumin to liver for 
conjugation via UDP-gluconuryl transferase to “conjugated bilirubin” and that gut bacteria 
generate water soluble urobilinogen, enterohepatic recycling and excretion in urine.
The major role of bile is in lipid, cholesterol and lipid soluble vitamin absorption with a minor 
role in excretion of bile pigments. It was expected candidates would describe the emulsification 
of fat via bile salts and lipid micelle formation to facilitate absorption.