L.10 PROTEIN DENATURATION

L10. Protein denaturation

1.Introduction

Denaturation is a process in which protein or nucleic acids lose the quaternary, tertiary and secondary structure that is present in their native state.

Denaturation is the result of the application of some external stress or compounds such as a strong acid or base, a concentrated inorganic salt or organic solvent.

If proteins in a living cell are denaturated, this results in disruption of cell activity and possibly cell death.

Denaturated protein can exhibit a wide range of characteristics, from loss of solubility to communal aggregation. This last effect resukts from the bonding of the hydrophobic protein to reduce the total area exposed to water.

In very few cases denaturation is reversible and protein can recuperate their native state when the denaturating factor is removed. This process is called renaturation.

2.Objectives

• Study the relation between the structure and the function of protein.
• Understand how temperature, pH and salinity affect to the protein structure.

3. Material

• 2x150mL beaker
• 4 test tubes
• Test tube rack
• 10mL pipet
• knife
• Glass marking pen
• potato
• distilled water
• hydrogen peroxide
• NaCl
• HCl

4.Procedure

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

First of all, we prepare 30mL of H2O2 10% in a beaker using a pipet, 30mL of HCl 10% in a beaker and 30mL of NaCl 50% in a beaker.

After, peel a fresh potato tuber and cut the tissue in five cubes of 1cm3. Weigh them and equal the mass.
Next label 5 test tubes (1,2,3,4,5)

Immerse 10 minutes your piece of potato inside HCl beaker and 10 minutes another piece of potato inside NaOH beaker. After, boil another piece of potato and with a mortar, mash up the thrid piece of potato.

Prepare 5 test tubes as indicated below:
1. Raw potato 
2. Boiled potato
3. Potato with HCl treatment
4. Potato with NaCl treatment
5. Mashed up potato

Next, add 5 mL H2O2 10% in each test tube and with a glass-marking pen mark the height of the bubbles. Measure it with a ruler.
Finally, compare the results of the 5 test tubes.

5. Observations

We can observed that the mashed up potato have more activity of the bubbles than other potato.


6. Conclusions

mashed > raw > NaCl (activity) > HCl (no activity) > boiled (no activity)







7. Questions

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

The temperature affect the enzyme X of the catalase.

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

When the pH changes for acid the catalase no activity while pH changes for a basic the catalase activity.

3. In which 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.