Investigate the effect of heat denaturation on the rate of enzyme activity (LC 2026) (Leaving Cert Biology): Revision Notes

Investigate the effect of heat denaturation on the rate of enzyme activity

Materials needed:

• Hydrogen Peroxide (substrate)
• Celery (contains enzyme catalase)
• pH buffer 9/10 (keeps pH constant)
• Thermostatically controlled water bath (varying temperatures: 30°C, 100°C)
• Washing up liquid (measure the rate of activity by volume of foam produced and breaks down the cell wall)
• Graduated cylinders
• Plastic droppers

Method:

1. Place 10 cm³ of celery, 1 drop of washing-up liquid, and 10 cm³ of pH buffer together in a graduated cylinder.
2. In another graduated cylinder, add 5 cm³ of hydrogen peroxide.
3. Place both graduated cylinders in a thermostatically controlled water bath set at 30°C for 2 minutes to allow all reagents to reach the exact temperature.
4. After 2 minutes, add the hydrogen peroxide to the graduated cylinder containing the other reagents.
5. Record the volume of foam produced after 1 to 2 minutes (the foam volume measures enzyme activity by indicating the amount of oxygen produced).
6. Repeat the experiment at 100°C.
7. Compare and comment on the volume of foam produced at each temperature.

Results:

Temperature	30°C	100°C
Volume of foam cm³ / 2 minutes	40 cm³	0 cm³

A large volume of foam was produced at 30°C, as this is the optimum temperature for the enzyme catalase, resulting in the greatest enzyme activity. At 100°C, no foam was produced because the heat caused the enzyme to become denatured, meaning it lost its 3D, folded, globular shape and no longer functions.