Investigating the changing effects of temperature on the activity of enzymes

Topics: Enzyme, Thermodynamics, Temperature Pages: 6 (1503 words) Published: December 5, 2013
Investigating the effects of changing temperature on the activity of enzymes Background information:
Renin is an enzyme that catalyses the coagulation of milk. It is found in the stomach of many animals and is used in making cheeses and junkets. It is found in the gastric juices or gastric mucosa of many mammals, including humans. In the human stomach, particularly those of infants, rennin works to curdle milk so that pepsin, another stomach enzyme, can further breakdown the proteins into absorbable amino acids called polypeptides. The aim of this experiment is to investigate the effect of changing temperature on the activity of enzymes. After experimentation the optimum temperature for enzyme activity will be established and the effects of varing temperature will be identified. Several experiments have already been conducted testing similar hypothesis and aims. All of these experiments also had very similar results. They found that approximately 37°C was the optimal temperature for rennin; it was at this temperature that the milk solidified quickest. Below that the reaction would occur far more slowly, sometime taking hours to complete, sometimes not reacting at all. Above 37°C, at approximately 45°C, the enzyme would become denatured and the reaction would never occur, even after the temperature was lowered back down to 37°C.1 Aim:

To investigate the reaction rate of the enzyme rennin at various temperatures Hypothesis:
It is predicted that a rise in temperature (to approximately 40°C) will increase enzyme activity. Wth further increase of temperature the protein enzymes will denature, lose their shape and therefore decrease in activity. Risk assessment:

Risk
Precaution
Burns from the hot water bath or hot plate
Ensure that all hot baths are set up in a visible area that is surrounded by minimal movement. If burns occur run affected area under cold water for 5-10 minutes depending on severity. Major burns should seek medical assistance Glass breakage can cause cuts/wounds

Use test tube rack to steady test tubes.
If glass breakage occurs immediately alert teacher, sweep up broken glass using a broom or dust pan and dispose of it in the appropriate bin

Apparatus:
Equipment
Rationale
1 hot plate
Heats water in hot bath for raising temperatures of milk and rennin above 30°C 1 hot bath
holds water which is heated by hot plate
1 ice bath (500mL beaker + 6-7 ice cubes)
Cools milk and rennin for testing temperatures below 30°C
3 regular test tubes
Holds the 20mLs of milk required for each trial
3 micro test tubes
Holds the small amount of rennin required
1 test tube rack
Holds regular sized test tubes in place so handling does not influence reaction 20mL of milk
Acts as substrate
2mL of rennin solution
Acts as enzyme for milk
1 large pipette
Gives precise measurment of milk
1 syringe
Gives precise measurement of rennin
2 thermometers
Measures temperature of milk and rennin when they are heated or cooled 1 timer
Measures time taken for milk to set

Method:
Constant Variables
Factor
Importance
Method of control
Volume of milk
The amount of milk determines the amount of substrate the enzyme has to work on which therefore effects the reaction rate. Keeping a constant amount of milk for each trial. Use Pipette Volume of rennin

The amount of enzymes determines the amount of chemical reactions possible to occur. Keeping a constant amount of enzymes for each trial- 1ml per every 10ml of substrate. Use a syringe Rennin and milk brought to the same testing temperature

Temperatures must be constant for both substances to ensure accuracy when they are mixed. Place each substance in a hot or cold water bath with thermometers in their test tubes. Remove from water bath when the same temperature has been reached Same time recorder

Timing must be accurate. With the same person reaction rate to press go and stop would be similar for each trial. Have the same time recorder for every trial...

Bibliography: Jirage, R 2009 Function of Rennin Enzymes, Ella Bache College, accessed 3 November 2013, .
Brooklyn College, n.d. Effect of temperature on enzyme activity, City University of New York, accessed 3 November 2013, .
Chidrawi, G, Robson, M & Hollis, S 2010, Biology in Focus, 1st edn, Cengage Learning, Australia
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