Enzyme Reactions and Temperature

Enzyme Reactions and Temperature
Purpose Aim ? To determine the effect of temperature on the rate of reaction of rennin when it reacts with milk to cause coagulation. Hypothesis ? As rennin is naturally found in the human stomach I believe that the optimal temperature for reaction will be approximately 37?C as this is the regular human body temperature. This is shown by the graph below.
Background Research Rennin is "an enzyme that catalyses the coagulation of milk, found in the gastric juice of the fourth stomach of young ruminants and used in making cheeses and junkets. Also called chymosin, rennet."2 It is also found in the gastric juices, or Gastric mucosa, of many other 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 Several experiments have already been conducted testing similar hypothesis and having similar aims. All of these experiments 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, sometimes 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. Name of enzyme ? Rennin Name of substrate ? Milk Materials - 50ml of full cream milk. - 10 small test tubes. - 5 140ml beakers. - Access to both hot and cold water supplies. - Pipettes. - Junket tablets. - Mortar and Pestle. - Distilled water. - Stopwatch. - Thermometer. Procedure Method -Using a pipette add 5ml of milk to each of the 10 small test tubes. Label 5 controls and 5 variables. -Place 100ml of water into each of the beakers, and using hot and cold water and thermometers raise the temperature of the first beaker to 20?C, the second to 30?C, the third to 40?C, the fourth to 50?C and the sixth to 60?C. These will be the water baths. -Place 2 test tubes, one control and one variable, in each of the water baths. -Whilst waiting for the milk to adjust temperature using the mortal and pestle grind up approx. 2 junket tablets and add 25ml of distilled water. -Recheck the temperature of the water baths and test tubes and make any necessary adjustments by adding hot or cold water to the beakers. -Add 4 drops of the rennin solution to each of the variable test tubes and time how long it takes for the milk to solidify. -Finally check your control test tubes to ensure that they have not solidified due to the temperature. Safety precautions that would need to be taken can be seen on included sheet. Results Temperature Time 20?C Did not solidify within time limit 30?C 2min 25sec 40?C 1min 20sec 50?C Did not solidify (most likely denatured) 60?C Did not solidify (most likely denatured) Also none of the control test tubes solidified during the experiment. Conclusion My conclusion is that my hypothesis was accurate. The optimal temperature based on the results was 40?C. However it is likely that this temperature could actually lie somewhere between 30?C and 40?C, most likely closer to 40?C. The reaction slows down considerably at 20?C taking longer than 15mins to clot. Above 50?C it appears that the enzyme was denatured as the milk did not coagulate at all. As none of the control experiments coagulated during the experiment we can safely assume that the results found were the product of rennin, not simply the effect of the increase in temperature on the milk. Discussion A control experiment must be performed to eliminate the possibility that the results are produced by a factor other than the one being tested. A Control experiment and the variable must be exactly the same except for on factor, the variable, which is what will be tested. My controls eliminated the possibility that the milk was simply clotting because of the increase in temperature. As the milk in the controls did not clot we can assume that the milk did indeed clot due to the rennin in the variable experiments. The variables I controlled were concentration of the rennin, quantity of substrate (milk) and enzyme, quality of the milk, and temperature. The concentration of the rennin was controlled by ensuring all rennin was taken from the same solution. The same quantity of both milk and rennin were used in order to make sure it is fair. All milk used was also taken from the same carton to ensure there were no differences in the quality of the milk. The temperature difference between the control and variable was also controlled by placing both test tubes in the same water bath. This ensured that both test tubes were the same temperature. The results were similar to what I expected. I was not sure if I would get a result for the 50?C experiment as I was not sure if the enzyme would have been denatured yet, but obviously it had been. The results supported my hypothesis to a certain degree, as the optimal temperature shown by the experiment was 40?C I was not able to test a smaller scale, so I have no way of knowing whether 37?C is the optimal temperature or another temperature around 40?C is. If I was able to do the experiment again I would most likely not conduct the experiment at 20?C, 50?C or 60?C and instead have more precise measurements in between 30?C and 45?C. If I did this far more accurate results would be achieved, and a more exact optimal temperate would be concluded. Accuracy could perhaps be improved by maybe taking a little more time, as the experiment was quite rushed and some results may not be completely accurate because of this. Safety precautions that would need to be taken can be seen on included sheet.

Enzyme Reactions and Temperature 8.4 of 10 on the basis of 3042 Review.