Protein digestion lab - Lab PDF

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Protein digestion lab: activity of pepsin and pancreatin ! Victoria Liu! March 27, 2018! Purpose: The objective of this lab is to investigate factors that determines egg albumin digestion. This is observed by placing egg whites into the test tubes that closely resemble human stomach and small intestine’s digestive juices at 37℃. ! Data table

Table I: Egg white digestion results after 24 hours Solutions

pH before

pH after

Results after 24 hours

6

6 • The egg white swelled by absorbing water. ! • The solution is transparent.

11

10 • The egg white swelled by absorbing sodium carbonate. ! • The colour of the egg white became whiter.! • The solution is transparent.

3. HCl

1

1 • The egg white swelled by absorbing HCl. ! • HCl dissolved a small part of the egg white.! • The solution is transparent.

4. Pancreatin and H2O

5

6 • Enzymes digested 1/3 of the egg white. ! • The solution at the bottom of the test tube turned cloudy.

1. H2O

2. sodium carbonate

5. sodium carbonate and pancreatin

6. HCL and pancreatin

10

1

9 • Enzymes almost digested the entire egg white. ! • The solution at the bottom of the test tube turned cloudy and white. 1 • The egg white swelled. ! • The colour of the egg white became whiter.! • The solution is transparent.

Solutions

pH before

pH after

Results after 24 hours

7. Pepesin and H2O

4

5 • The egg white is swelled. ! • The solution became cloudy.

8. sodium carbonate and pepsin

10

9 • The egg white swelled by absorbing sodium carbonate. ! • The colour of the egg white became whiter.! • The solution is transparent.

1

1 • The enzyme digested the entire egg white.! • The solution at the bottom of the test tube turned cloudy and white.

9. HCl and pepsin

Analysis questions: 1. In what test tube was the egg most digested?! Test tube number nine digested most egg whites. ! 2. Which test tube closely resembles the human stomach?! Test tube number nine closely resembles the human stomach because it contains hydrochloric acid and pepsins, which make up the gastric juices in human stomach. ! 3. why were the test tubes stored in the incubator overnight?! The test tubes were stored in the incubator overnight because the temperature in the incubator resembles the human body’s temperature. By placing the tubes in a stimulated human body’s temperature allows the digestion of proteins to successfully occur. ! 4. At what temperature were the tubes incubated?! The tubes are incubated at 37 degrees celsius, which is the human body’s temperature. ! 5. Under ideal conditions, at what pH would you expect protein digestion to occur?! Under ideal conditions, protein digestion should occur at 1- 2 pH level, because proteins are digested by pepsins in the 2pH acidic gastric juices from the stomach.The low pH level of the gastric juices stops the activity of the salivary amylase and promotes the activity of pepsins to break down proteins into polypeptides. ! 6. What could you have done to simulate the digestion that occurs in the stomach?! To simulate the digestion that occurs in the stomach, I would first combine the hydrochloric acid and pepsin in a test tube. It closely resembles the gastric juice in the stomach, HCl are secreted from the food and pepsins are the digestive enzyme to break down protein into peptides. Second, place a small cube of egg white into the test tube, egg whites are made of proteins. Third, shake the test tube to simulate the stomach’s mechanical digestion of food through peristalsis. Lastly, the test tube should be placed in an incubator at 37 degrees celsius for 24 hours to digest the egg white. !

7. Why was a test tube of water and egg set up?! The test tube of water and egg is set up because all enzymatic digestion of food requires the presence of water. Hydrolysis occurs in chemical reactions to breakdown the major components of foods, such as lipids, carbohydrate and proteins with water. ! 8. What was the reason for adding sodium bicarbonate solutions to a test tube?! The reason for adding sodium bicarbonate solutions to a test tube is because pancreatic enzymes functions best at a slightly basic pH and sodium bicarbonate neutralize chyme, which is acidic. The slightly basic pH of the chyme helps the pancreatic enzymes to break down the components of food more efficiently. ! 9. After interrupting the data from this lab, a student concludes that HCl causes protein digestion? Is this student correct in their assumption? Give reasons to support your answer! This student is correct, HCl causes protein digestion in the stomach. HCl is the major component of the gastric juice in the stomach. It maintains the acidic level of the gastric juice at the pH of 2.0. Pepsins are powerful digestive enzymes for proteins in the gastric juice. Its inactive form is known as pepsinogen, pepsinogens are only activated when they are in contact with hydrochloric acids. Once the pepsinogens are activated by HCl to pepsin, the pepsins digest proteins into polypeptides....