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How Does Changing the Substrate Concentration Affect the Rate of an Enzyme Controlled Reaction?

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Introduction

How Does Changing the Substrate Concentration Affect the Rate of an Enzyme Controlled Reaction? Aim The aim of my investigation is to find out how changing the substrate concentration affects the rate of an enzyme controlled reaction. The enzyme is catalase & the substrate is hydrogen peroxide. The catalase breaks down the hydrogen peroxide and the end result is water and oxygen. I will measure the amount of oxygen gas produced. Prediction I think that the higher the concentration of hydrogen peroxide is, the rate of reaction will be quicker & the most gas will be produced with the highest concentration. Explanation Enzymes and substrates have complimentary shapes. When a substrate collides with an enzymes active site, (Lock and Key) bonds within the substrate are broken & the products are released. If a beaker contains a low substrate concentration, this means there are few substrate molecules present. The reaction will be slow; this is because there is less chance of a collision between the enzyme & the substrate, this means that fewer products will be released. Whereas if another beaker has a high concentration of substrate, the reaction rate will be much more vigorous, this means more collisions and more products being released. ...read more.

Middle

Step 4-Get a boiling tube and measure out 1g of yeast into it, get a clamp stand. Step 5-Place the boiling tube containing the yeast into the clamp stand so it is just above the water in the trough. Step 6-Get another test tube or boiling tube and place a 20% concentration of hydrogen peroxide into it. Use the guide on the pipette to measure out 4ml. Step 7-Get a delivery tube & bung, place the transparent 'L' shaped end underneath the lip of the measuring cylinder in the trough, so it is just inside the cylinder. Step 8-Get a stopwatch. Pour the hydrogen peroxide into the tube with the yeast in it, and then very quickly place the bung securely into the tube. Once the bung is securely in place, start the stopwatch. Once it has reached 10 seconds, take the first reading of how much gas has been produced, do this again when it reaches 20 seconds and take a final reading at 30 seconds. Step 9-Once you've completed this for the 20% concentration, repeat it with concentrations of 15%, 10%, 5%, and 2.5% concentrations. Repeat each concentration, including the 20% 3 times in total. Results Table Amount of gas (Cm3) ...read more.

Conclusion

I had two anomalous results. For 10 seconds, the 2.5% concentration of hydrogen peroxide collected more gas than the 5% at 10 seconds. This lowers the reliability of my results. Something that could have affected the results is the equipment. The first delivery tube we used got clogged up so we had to change it, this new tube could have been wider or shorter than the first one. I carried out repeats then took my averages. Another thing that could have affected my results is the people. Something that could have affected the results is the measuring of the yeast and hydrogen peroxide, towards the end of the experiment we were running out of time, and may have taken wrong amounts of yeast and substrate which could be why there are anomalous results. I feel like my results aren't as reliable as they could be, if we did the experiment again and had more time I think we would have more reliable results because we wouldn't have messed up the amounts of yeast and hydrogen peroxide. If there were more concentrations I would be able to explain more about the rates of reaction because if there was a 25% or a 50% concentration I would have a more reliable set of results because I would have repeated it 3 times and had more results to work with. ...read more.

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