Q.18 What is the role of bile salts in the mammalian digestive system?
(A) Bile salts convert pepsinogen to pepsin, and thus facilitate protein digestion
(B) Bile salts emulsify fat, and thus aid in fat digestion
(C) Bile salts are excretory products produced by the liver, and do not participate in digestion
(D) Bile salts facilitate digestion of all types of macromolecules in the small intestine
Correct Answer: (B) Bile salts emulsify fat, and thus aid in fat digestion
Bile salts, produced by the liver and stored in the gallbladder, play a critical role in lipid digestion within the mammalian small intestine. They act as emulsifiers, breaking down large fat globules into smaller droplets to increase surface area for pancreatic lipase action.
Option Analysis
(A) Bile salts convert pepsinogen to pepsin, and thus facilitate protein digestion
This is incorrect because pepsinogen activation to pepsin occurs in the stomach via hydrochloric acid, not bile salts, which are released into the duodenum.
(B) Bile salts emulsify fat, and thus aid in fat digestion
This is correct. Their amphipathic nature allows micelles formation, solubilizing fats for efficient enzymatic breakdown and absorption.
(C) Bile salts are excretory products produced by the liver, and do not participate in digestion
Incorrect; while derived from cholesterol for excretion, bile salts actively emulsify lipids and are 95% reabsorbed via enterohepatic circulation.
(D) Bile salts facilitate digestion of all types of macromolecules in the small intestine
Wrong; they specifically target fats, not carbohydrates, proteins, or nucleic acids, which rely on other enzymes.
The role of bile salts in mammalian digestive system centers on emulsifying fats to enable efficient digestion and absorption in the small intestine. Synthesized from cholesterol in the liver, these amphipathic molecules are released via bile into the duodenum upon fat detection.
Bile salts reduce surface tension between water and lipids, forming micelles that suspend fat droplets. This process exposes more lipid surface for pancreatic lipase, converting triglycerides to monoglycerides and fatty acids for uptake by enterocytes.
Beyond digestion, bile salts aid fat-soluble vitamin (A, D, E, K) absorption and maintain cholesterol homeostasis through fecal excretion. Deficiencies, like in cholestasis, impair fat digestion leading to steatorrhea.
