Digestion in the Small Intestines

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EXPERIMENT 13
DIGESTION IN THE SMALL INTESTINES

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ABSTRACT
The small intestine serves as the site of major digestive and absorptive processes. In this experiment, the action of pancreatic enzymes on representative samples of each food group under different conditions, such as increased/decreased pH and presence of other substances, were observed. A pancreatin solution was first prepared from a hog pancreas and was completely neutralized using 0.5% Na2CO3. Afterwards, 3 mL each of the neutral pancreatin solution was placed in 7 test tubes and were further added with other specified reagents. The test tubes containing HCl were not effective in digesting the biomolecules since pancreatin is only active in moderately alkaline conditions, as observed in test tube 2. Data obtained from test tubes 3-7 were inconclusive and would most likely subjected to errors, thus, producing anomalous results.

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DISCUSSION OF DATA AND RESULTS
The small intestine is divided into three segments, namely, (1) duodenum which originates from the pyloric sphincter of the stomach and extends for 25 cm, (2) jejunum that is approximately 2.5 m long, and (3) ileum which is 3.6 m long and joins the large intestine at the ileocecal sphincter. (Tortora & Anagnostakos, 1990) Major portions of digestion and absorption occur in the small intestine for three reasons: (1) food entering the intestine have undergone extensive preliminary breakdown due to the mechanical and chemical processes in the mouth and stomach; (2) the small intestine receives enzymatic secretions which are necessary in the complete digestion of each major food group; and (3) food stays in the small intestine for a relatively long period of time which allows the enzymes to completely act upon the biomolecules. (Chaffee & Greisheimer, 1975) Pancreatin is a combination of pancreatic enzymes, namely, amylase, lipase, and protease—each individual component act on starch, lipids, and proteins, respectively. The solution was prepared from a hog pancreas which was washed with sodium hydroxide (NaOH) and neutralized with 0.5% sodium carbonate (Na2CO3). Pancreatin and other intestinal enzymes are active at moderately alkaline pH as compared to stomach enzymes which require acidic conditions for them to be active. (Indiana University, 2010) Table 1. Summary of results for the action of pancreatic enzymes TEST TUBE #| RESULTS|

1| Hard-boiled egg white: Digestion occurred|
2| Hard-boiled egg white: No digestion|
3| The color of iodine disappears.|
4| The color of iodine disappears.|
5| Titration: 2 drops of NaOH used (overtitrated)|
6| Titration: 1 drop of NaOH used|
7| Titration: 1 drop of NaOH used|

In the experiment, equal slices of hard-boiled egg whites were dropped into test tubes 1 and 2, which were both containing neutral pancreatin, and 0.5% Na2CO3 and 0.01N hydrochloric acid (HCl), respectively. From these combinations of reagents, it is clear that test tube 1 would contain a basic solution while test tube 2 would contain an acidic one. Observations showed that digestion occurred in test tube 1 while no digestion was seen in test tube 2. The rate at which digestion occurs is affected by various factors, but more importantly by the dependency of the digestive processes on enzyme activity. Enzymes require certain optimal conditions for them to be able to act on specific substances effectively and efficiently. Temperature and pH are two factors that greatly affect enzymatic activity and reactions. The rate of enzyme-catalyzed reactions generally increases when temperature is increased, provided that the temperature increase is within the range at which the enzyme does not denaturize and retains full activity; on the other hand, most enzymes would have a characteristic pH at which their activity is maximal and a decrease or increase of the pH...
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