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MCAT Biology Question — Bile Salts

In response to CCK, the gall bladder will release bile salts into the duodenem where they aid in fat digestion. Which of the following best describes the function of bile salts?

 

A) Breakdown of fat molecules by cleaving the linkage between the fatty acid chains and the glycerol backbone

B) Increasing the speed at which fat is digested by increasing the surface area over which enzymes have to work

C) Binding to lipid molecules for transport in the blood in the form of chylomicrons from the intestines to the liver, where the fat will be processed.

D) Neutralizing the HCl in stomach acid allowing the fatty acids in lipids to be processed in the carboxylate anion form rather than the protonated acid form.

 

Explanation

 

Bile salts serve to emulsify the fat as it enters the duodenum. That is, they don’t break the chemical bonds within the molecule itself, they break up large fat globules into smaller lumps, creating more surface area for lipase to act. This increase in surface area lets lipase act much more quickly to digest the fats. Therefore, B is the

 

A: This is the function of lipase, not bile salts.

 

C: This is the function of apolipoproteins.

 

D: Stomach acid is neutralized with bicarbonate from the pancreas.

 

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