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To find out what factors affect the rate of reaction between rennin and milk.

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Introduction

Aim To find out what factors affect the rate of reaction between rennin and milk. SECTIONS OF THIS REPORT Research 1. Enzymes 2. Enzyme Action 3. Specificity 4. Reversibility 5. Temperature 6. pH 7. Other Factors which could Affect the Rate of an Enzyme 8. Rennin Predictions 9. Temperature 10. pH 11. Concentration of Enzyme 12. Which Variable has the Greatest Relative Effect? Planning 13. Measuring the Rate of Reaction 14. Quantities 15. Plan for Temperature 16. Plan for pH 17. Plan for Concentration of Enzyme 18. Accuracy Results 19. Temperature 20. pH 21. Concentration of Enzyme Conclusions 22. How Temperature Affects the Rate of Rennin 23. How pH Affects the Rate of Rennin 24. How the Concentration of Enzyme Affects the Rate of Rennin 25. Overall Conclusion RESEARCH I know that Rennin is an enzyme, so before conducting this experiment I am first going to do some research into enzymes and their effects. 1. Enzymes Enzymes are large globular molecules of which the vast majority are protein in nature, though some, known as 'ribozymes' are made of RNA. Enzymes have catalytic properties; in other words, they alter the rate of reaction without themselves undergoing a permanent change. Most chemical reactions require an initial input of energy, called activation energy, to enable them to occur. Enzymes reduce the need for activation energy and so allow reactions to take place more readily and at lower temperatures than would otherwise be necessary. This can be seen in the graphs. 2. Enzyme Action Enzymes, as biological catalysts, can be used in both anabolism (the build up of simple chemicals into complex ones) and catabolism (the breakdown of complex chemicals into simpler ones), although the latter is more common especially in the animal digestive system. As shown in the next diagram it is thought that the substrate molecules fit precisely into the enzyme molecules. This theory is referred to as the lock and key mechanism. ...read more.

Middle

For, though I know rennin to react best in acidic conditions, by adding hydrochloric acid to provide favourable conditions, I would be unsure whether it was the acid or the temperature having the most effect on the reaction, and I would have inaccurate results. Also, hydrochloric acid separates milk itself, so the reaction would begin before the rennin was added. When heating or cooling, I will do exactly the same to both the milk and the rennin, to ensure that both are at the same temperature and it is not just the milk being heated while the rennin remains at room temperature, which would, of course, effect the results I received. For if the milk was at 80�C, but I had not heated the rennin, the enzyme would still be able to react with the milk until eventually the rennin itself had reached a high temperature and was denatured. To ensure that the enzyme and substrate remain at the required temperature I am going to pour them together and watch for the reaction whilst they are still in their set conditions, ie I will not take the boiling tube out of the water bath. I am going to use ice and water baths, heated or cooled to different temperatures to achieve the correct temperature in the enzyme and substrate. 16. Plan for pH I am going to use the three categories of acid, neutral and alkaline to test how pH affects the rate of the enzyme rennin. Whilst studying the affects of varying the pH, I am going to ensure that all other variables are constant. Therefore, I will continue to use 2ml of milk and 4 drops of rennin. The temperature I shall conduct these experiments at will be room temperature (27�C). I have decided on this temperature because it is hot enough to provide the enzyme and substrate with enough energy for a successful collision and yet it is not quite ideal. ...read more.

Conclusion

25. Overall Conclusion From the results and conclusions of the three independent experiments, I am able to state that the ideal working conditions for rennin is in a temperature of 40�C, in a pH of 1 and in a maximum concentration of enzyme. I believe that my predictions were correct and temperature does have the greatest relative effect; for the concentration of rennin will not completely stop the reaction or dramatically increase it, because enzymes can be used over again. pH is a very important factor because in alkaline conditions the enzyme is denatured and the difference in reaction times between neutral and acidic conditions are quite great. However, by looking at the results for temperature I can see that it causes the reaction to stop above 40�C because the enzyme is denatured and below 20�C it has the effect of slowing the reaction dramatically and so I was unable to measure it. The considerable difference between the times for 20�C and 40�C suggests to me that just small variations in temperature have great affects on the rate of reaction. The primary limitation with this experiment was the judgement by eye of when the milk had fully clotted, as this is not going to be completely accurate and the same for each experiment. I considered conducting the experiment in another way, but as no gas, which I could collect for example, was produced, the only other way was to weigh the amount of curds and whey created. However, with thought I reasoned that the factors I was testing would not affect the actual amount of curd produced, just the speed at which it was produced. If I was to do this investigation again I would use more detailed and smaller ranges of readings because for many of the experiments I got no result, as it appears rennin is very specific in its ideal conditions. To conclude I have found rennin to be denatured in alkali conditions and/or temperatures over 60�C, but as predicted, to work best at 40�C, at pH 1 and with the maximum amount of the enzyme possible. ...read more.

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