P10. Protein Denaturation

Introduction:

• Denaturation is a process in which proteins 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 (heat and pH change) or compounds such as a strong acid or base, aconcentrated inorganic salt or organic solvent. 
• If proteins in a living cell are denatured, this results in disruption of cell activity and possibly cell death.
• Denatured proteins can exhibit a wide range of characteristics, from loss of solubility to communal aggregation. This last 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 denaturing factor is removed.
•  This process is called renaturation.

Objectives:

1. Study the relation between the structure and the function of proteins.
2. Understand how temperature, pH, and salinity effect to the protein structure.

Hypothesis:

• Catalase denaturated proteins.

Materials:

• 2x250 mL beaker
• 4 test tubes
• Test tube rack
• 10 mL pipet
• Knife
• Glass marking pen
• Potato
• Distilled water
• Hydrogen Peroxide
• NaCl
• HCl

Procedure:

Prepare 30mL of H₂O₂  10% in a beaker (use a pipet), put 30mL of HCl 10% in a beaker.

Prepare 30mL of NaCl 50% in a beaker.

Peel a fresh potato tuber and cut the tissue in five cubes of  1cm³. Weigh them and equal the mass.

Label 5 test tubes (1,2,3,4,5).

Immerse 10 minutes your piece of potato inside HCl and NaOH  beaker.

Boil another piece of potato.

Mash up the third piece of potato.

Prepare 5 test tubes: one of raw potato, boiled potato, potato with HCl, potatp with NaCl, and mashed up potato.

Add 5mL H₂O₂  10% in each test tube.

With a glass-marking pen mark the height of the height of the bubbles.

Compare the results of the test 5 test tubes.

Conclusions and coments:

The temperature and acidity are more able reducing the salinity.

• Independent variable: treatment of each potato (pH, temp....)
• Dependent variable: the height of the bubble
• Experimental Group: The rest test tubes
• Control Groups: Raw

RESULTS:

• Mashed: 74mm
• NaCl: 39mm
• HCl: 35mm
• Boiled: 37mm
• Raw: 40mm