Lipid Hydrolysis
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Introduction
The bulk of enzymatic activity for the digestion of protein and fat occurs in the small intestines. However, there are several minor digestive processes that start in the mouth and stomach.
As acidic chyme leaves the stomach and enters the small intestines, the pancreas is stimulated to release pancreatic juices. These juices contain amylase, different proteases, and lipase. Additionally, the gall bladder releases bile into the small intestines. Bile is used to emulsify fats increasing the surface area that lipase can act upon. As is true in carbohydrates, protein and fats are broken into their smallest units to allow for absorption.
In this lab we will be using lipase to study the digestive process that takes place before absorption of fats. Additionally, you will demonstrate the impact bile salts have on lipid digestion. You will also determine how changes in temperature and pH may affect the digestive process.
Lipid Hydrolysis
The majority of dietary fat consists of triglycerides. Triglycerides are broken down into glycerol and fatty acids by lipases.
The salivary glands do possess lingual lipase that may initiate digestion of short chain fatty acids in the mouth, but the majority of fat digestion occurs in the small intestines.
Digestion of fats is slightly more complicated than carbohydrate and protein digestion because fats must first be emulsified by bile to increase their surface area and to allow the water-soluble lipases to get to the triglyceride molecules. Increased surface area makes lipase more effective.
The basis of the assay used in this laboratory exercise is the fact that lipase breaks fats down into fatty acids. As the name implies, fatty acids are acids and so have a lower pH. The heavy cream used in this experiment has added to it a compound called litmus. Litmus is an alkaline solution that turns from blue to pink in the presence of acid. Therefore, the pH will decrease as lipids are hydrolyzed and produce fatty acids, and this decrease in pH will be evidenced by the color change from blue to pink.
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