Pepsin Experiment Protocol

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20/04/2013

Pepsin Experiment
Experiment protocol to test the effect of temperature on the enzyme pepsin

Lab Day:

Tuesday

Lab Time: 10-1pm Are you in Lab G20 (furthest from BSB Student Office) or Lab G21 (closest to BSB Student Office)?: G20 Demonstrator Name: Tamsin Peters Names of Group Members:     Roanna Humphries Daniel Markus Nicholle Cooke-Hayes Dean Do Rosario Pepsin

Name of Enzyme You are Investigating:

Table of Contents
Table of Contents ....................................................................................................... 1 Enzyme Background ................................................................................................. 2 Hypothesis ................................................................................................................ 3 Equipment/Apparatus: ............................................................................................ 3 Reagents/Material: ................................................................................................... 3 Supplied by student: ............................................................................................. 3 Supplied by UNSW: .............................................................................................. 3 Method: ..................................................................................................................... 4 Producing pepsin solution .................................................................................... 4 Diagrams: ...................................................................................................................5 Risk Assessment ....................................................................................................... 6 Emergency Procedures .......................................................................................... 7

1

Enzyme Background
Pepsin is an enzyme present in the digestive system of many most mammals, birds, reptiles, and fish. Its purpose is to catalyse the reaction of protein breakdown by water and hydrochloric acid (HCL) in the stomach. While proteins are made in the body by replicating sections of DNA, many proteins are also received through digestion of food. Structurally, proteins are long chained molecules made from amino acids. In order to breakdown these protein molecules, hydrolysis takes place which is where water breaks down into a single H+ cation and a OH- anion. These react with the protein segments to form individual amino acids by destroying the peptide bonds which holds protein segments together. These peptide bonds are strong covalent double bonds which, with only water would be almost impossible to breakdown. In the body this is done through the aid of the enzyme Pepsin and HCL at a low pH of 3-4. The HCL has a dual purpose in protein digestion. It helps water by providing more H+ ions which can be dissociated from acid with less energy than from water. It also lowers the pH to the optimal pH range for pepsin. This in turn allows the pepsin to work at max efficiency as it also works to lowering the energy required to break the peptide bonds in order to digest protein. Another benefit of pepsin is that due to its specific pH working range, it is inactive at a pH higher than 5. Once the partly digested protein enters the small intestine, the pH rises above 5 towards a pH of 7 due to a lack of HCL this in turn inactivates pepsin allowing the small intestine to secrete enzymes to further breakdown protein in the body.

2

Hypothesis
Our Hypothesis is that pepsin will work at optimum efficiency at a temperature of about 37°C. If the temperature is reduced, pepsin will work at a diminished rate due to a lack of energy. If the temperature is increased, pepsin will begin to denature.

Equipment/Apparatus:
         12 Test tubes Test tube rack 6 Beakers Water baths (0-4°C (ice bath), 35°C, 45°C, 50°C, 60° and 90-100°C) Stop...
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