L10: PROTEIN DESNATURALITION I

1. INTRODUCTION

Desnaturation is a process in which proteins or nucleic acids lose the quaternary, tertiary and secondary structure that is present in their native state. Desnaturation is the result of the application of some external stress ( heat and pH change) or base, a concentrated inorganic salt or organic solvent.

If proteins in a living cell are denatured, this results is disruption of cell activity and possibly cell death. Denatured proteins can exhibit a wide range of ring characteristics, from loss of solubility to communal aggregation.
This las effect results from the bonding of the hydrophobic proteins to reduce the total area exposed to water. In very few cases denaturation is reversible and proteins can recuperate their native state when the denaturation is reversible and proteins can recuperate their native state when the denaturing factor is removed. This process is called renaturation.

2. OBJECTIVES

- Study the relation between the structure and the function of proteins,

- Understand how temperature, pH snd salinity affect to the protein structure.

3. MATERIAL

- 2X50 mL beaker
- 4 test tubes
- Test tubes rack
- 10 mL pipet
- Knife
- Glass marking pen
- Potato
- Distilled water
- Hydrogen peroxide
- NaCl
- HCl

3. PROCEDUCE

In this experiment we are going to test the catalase activity in different environment situacions. We are going to measure the rate of enzyme activity under various conditions, such as different pH values and temperatures. We will mesuare catalase activity by observing the oxygen gas bubbles when H2O2 is destroyed. If lots of bubbles are produced, it means the reaction is happening and the catalase enzyme is very active,

-  Prepare 30 mL of H2O2 10% in a beaker ( use a pipet).
-  Prepare 20 mL of HCl 10% in a beaker.
-  Prepare 30 mL of NaCl 50 % in a beaker.
-  Peel a fresh potato tuber and put the tissue.
- Label 5 test tubes (1,2,3,4,5).
- Immerse 10 minutes your piece of potato inside HCl and NaOH beaker, and mashed up the potato.
- Add 5 mLH2O2 10% in each test tube.
- With a glass- marking pen mark the height of the height of the bubbles.
- Compare the results of the 5 test tubes.

4. OBSERVATIONS 

- Independent variable: treatment of each potato.
- Dependent variable: the height of the bubbles.
- Experimental Group(s): the rest.
- Control Groups: treatment of each potato.
- Constants: size, amount of H2O2, time...

5. CONCLUSION

Mashed > Raw > NaCl > HCl > Potato boiled.

6. QUESTIONS

1. How did the temperature of potato affect the activity of catalase?

The enzime X of the catalase.

2. How did the change of the Ph of the potato affect the activity of the catalase?

The pH change for acid the catalase no activity while ppH change for a basic the catalase activity.

3. In wich potato treatment was catalase the most active? Why do you think this was?

The mashed up potato , because when we mashed up the potato break the enzyme X.