Question

Bile secretion is proportional to the concentration of
A. Protein
B. Fat
C. Carbohydrate
D. None of the above

Answer 1

Hint:
Bile, also called gall, yellowness secretion that's produced within the liver and passed to the gallbladder for concentration, storage, or transport into the primary region of the tiny intestine, the duodenum. Its function is to help within the digestion of fats within the duodenum.

Complete answer:
Bile is an aqueous, alkaline, greenish-yellow liquid whose main function is to emulsify fats within the bowel and eliminate substances from the liver. The liver produces 0.25-1L of bile per day.

Constituents of bile:
Bile is created of bile acids, cholesterol, phospholipids, bile pigments (such as bilirubin and biliverdin), electrolytes and water. These are split into two main groups, called the bile acid-dependent and bile acid-independent components:
The bile acid-dependent component is produced by hepatocytes. The hepatocytes secrete bile acids, bile pigments and cholesterol into canaliculi, which are small channels that transport the steroid dependent portion towards the bile ducts.
The bile acid-independent component is formed by the ductal cells that line the bile ducts. These cells secrete an alkaline solution – just like the fluid made by duct cells.

Bile Pigments:
Bile also contains bile pigments which are excretory products of the liver and include biliverdin and bilirubin. Bilirubin may be a breakdown product of haemoglobin and is conjugated within the liver and secreted into bile. Bile pigments are normally excreted within the faeces and make the faeces appear brown. Problems within the liver or biliary tree often end in the buildup of bilirubin within the blood, which manifests as jaundice.

Circulation of Bile Acids:
Bile passes out of the liver through the bile ducts and is concentrated and stored within the gallbladder. During and after a meal, bile is excreted from the gallbladder by contraction and passes into the duodenum through the common channel. Most of the bile acids are reabsorbed within the terminal ileum and returned to the liver via the hepatic portal. The liver then extracts the bile salts. The enterohepatic circulation allows the liver to recycle and preserve a pool of bile acids.

Therefore, the correct option is b, fat.

Note: Bile Acids and Bile Salts:
There are two primary bile acids: Cholic acid and chenodeoxycholic acid
When these bile acids are conjugated with the amino acids glycine and taurine, they form bile salts. Bile salts are more soluble than bile acids and act as detergents to emulsify lipids. Bile salts are amphipathic which suggests they need a hydrophobic end which is lipid-soluble and a hydrophilic end which is water-soluble. This structure allows bile salts to emulsify fats into smaller droplets, increasing the expanse for lipids to be countermined by duodenal lipases. The bile acids coat the products of lipid breakdown yet as cholesterol and phospholipids to create spherical structures referred to as micelles. Micelles play a very important role within the digestion of fats and transport their contents to the intestinal epithelium where they will be absorbed. However, the bile acids don’t enter the gut epithelial cells with the lipids, rather they recirculate back to the liver, via the enterohepatic circulation.