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Enzymes Investigation

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Introduction Enzymes are proteins that speed up the rate of reaction at physiological temperatures without being used up or changed themselves. The nature of neither the end product nor the reaction equilibria is changed by the enzyme, just the rate at which it is reached. They are globular proteins, composed of polymers of amino acids. Enzymes act by becoming part of the reaction, creating a new pathway with a lower activation energy (EA), than the than the energy needed to carry out the original reaction, as seen in the graph to the left (Campbell, 1996). The active site of an enzyme is actually a very small proportion of the total volume. The substrate binds to the active site, forming an enzyme-substrate complex. The substrate is held in place by weak interactions such as hydrogen bonds and ionic bonds. The substrate is converted to the product and then leaves the active site, freeing it to take up another substrate molecule. As the enzyme is neither used up nor changed in the reaction it means a very small amount of enzyme can have a huge effect. Enzymes are usually specific and catalyse on particular type of reaction or even only one specific reaction. ...read more.


* To improve accuracy an average time was obtained for each pH buffer solution by the repetition of the above method. Risk Assessment In this investigation there are a number of risks to safety: Risk Possible hazard Precautions Glass-wear Could be broken and cut somebody. Care should be taken when handling glass-wear. Breakages should be reported and cleaned up immediately. pH buffers Could cause harm to skin or clothes if spilled. Protective clothing (lab coats, goggles, gloves, etc) should be worn. Spills should be reported and cleaned up immediately. Scissors/craft knife If used incorrectly could cause harm. Care should be taken when using these instruments; perhaps the teacher should do this. Water bath If too hot could scold. Should be kept at a safe temperature and hands should be kept out of the water. Pepsin solution Could cause harm to skin or clothes if spilled. Protective clothing (lab coats, goggles, gloves, etc) should be worn. Spills should be reported and cleaned up immediately. A first aid kit, including eyewash should be kept to hand at all times. Results PH 1 2 3 4 5 6 Time (mins) 0 10.26 8.52 15.42 22.50 0 Rate (1/time) ...read more.


The pH in the stomach can vary greatly between pH1 and pH5 or more, so it would be acceptable to think that pepsin would work between these pHs. However, pepsin works in a much narrower pH range, from the table and graph we can see that the pepsin worked most effectively at pH3, and worked very slowly in only three other buffers, therefore between somewhere between ph2 and pH4 is pepsin's optimum. This is probably closer to pH 2 as it worked faster there than at pH 4. Further Work To improve on this investigation we could carry out some further experiments. * Intermediate pHs should be tested to determine the exact optimum pH. * The effect of temperature should be tested so we could find the perfect conditions for pepsin. * Varying the substrate and enzyme concentrations would also give us an idea of the perfect working conditions for pepsin. * There were a number of errors in our investigation that should be thought about: o The buffers may not have been the exact pH stated. o The pepsin solution may not have been exactly 1%. o The film may not have been cut exactly to size. o The temperature of the water bath fluctuated slightly. o The amount of agitation to each tube may not have been the same. o o o o ...read more.

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