In the duodenum, most dietary lipids are emulsified into droplets, with the majority of particles ranging in size from 1–100 µm in diameter. After about one hour of digestion, smaller emulsified droplets in the 1–50 µm range can be detected. Which of the following amphipathic molecules is responsible for this change?
A. pepsin
B. bile salts
C. glycogen
D. pancreatic lipase
Click for Explanation
Triglycerides are hydrophobic dietary fats. In order to be absorbed by the digestive system, bile salts create small emulsions containing triglycerides, essentially breaking the fat globules apart into smaller and smaller pieces. Bile salts themselves are created in the liver and stored in the gall bladder prior to release. Since bile salts are amphipathic, they can interact with the hydrophobic triglycerides and the aqueous environment of the digestive tract lumen.
A, pepsin, incorrect, Pepsin is the active catabolic enzyme of the zymogen pepsinogen, secreted by chief cells in the stomach.
B. bile salts, correct.
C. glycogen, incorrect, Glycogen is a branched polymer of glucose found primarily in muscle and liver cells.
D. pancreatic lipase, incorrect, pancreatic lipase will enzymatically cleave apart triacylglycerides so that their components can be absorbed. Pancreatic lipase will not break the globules apart into smaller globules.
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