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Enzyme theory: explore the properties and functions of enzymes

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Introduction

Introduction In this experiment I will attempt to investigate how the change in temperature effects the catalyse reaction and what the optimum temperature is. Key factors Key factor (variable) Reason for controlling How it is going to be controlled Temperature of hydrogen peroxide H202 I am going to control this variable because if the temperature of the hydrogen peroxide was higher or lower then the right temperature the test wouldn't be fair and my results could be affected because a different temperature would result in a different froth height. I am going to control the temperature by placing the hydrogen peroxide into a water bath with the exact temperature for at least 3 minutes. Temperature of yeast I am going to control this variable because if the temperature of the yeast was higher or lower than the right temperature the test wouldn't be fair and my results could be affected because a different temperature would result in a different froth height. I am going to control the temperature by placing the hydrogen peroxide into a water bath with the exact temperature for at least 3 minutes. Water temperature I am going to control this variable because if I didn't the hydrogen peroxide and the yeast will be at different temperatures because I will use the water to heat the hydrogen peroxide and yeast. I am going to control this variable by having the water placed in a water bath which will keep the water at a constant temperature. Volume of hydrogen peroxide I am going to control this variable because if I didn't my results would differ to the results I would have if my results where accurate and this wouldn't be a fair test. I am going to control this variable by using a pipette to pour the hydrogen peroxide into the small measuring cylinder (10cm3). Volume of yeast I am going to control this variable because if I didn't my results would differ to the results I would have if my results where accurate and this wouldn't be a fair test. ...read more.

Middle

At this point the enzyme is said to be denatured. With a fixed amount of enzyme the addition of more substrate will cause the rate of reaction to increase until all the enzyme molecules are being used. At this point the rate of reaction levels off because the enzyme is limiting the reaction. An increase in the amount of enzyme will cause a proportional increase in the rate of reaction provided that there is excess substrate. Enzymes work in a narrow range of pH outside of which the hydrogen bonds between the NH and CO groups are broken. A solution that prevents changes in pH is called a buffer solution. Scientific knowledge used to plan Structure in enzymes The different levels of protein structure are known as primary, secondary, tertiary, and quaternary structure. There are 20 common amino acids are classified by their functional group, or their "R" group. When the weak hydrogen bonds that help the enzyme take its shape break because of the heat the enzymes have become denatured. Primary structure The primary structure is the sequence of amino acids that make up a polypeptide chain. 20 different amino acids are found in proteins. The exact order of the amino acids in a specific protein is the primary sequence for that protein. AA1-AA2-AA3-AA4-AA5-AA6-AA7-AA8-AA9-AA10-AA11-AA12 etc This structure twists and turns because of the R groups in the amino acids. Every R group is different If you zoom in on one of the amino acids and look at the structure you will see: H H R NH3 - C - C - C - CooH H H R Because of the attraction between the r groups weak hydrogen bonds are formed, these bonds are what hold the structure together and if the enzyme its alpha helix or beta sheet shapes. Secondary structure The amino acids form regular repeating patterns folding along the protein back bone. ...read more.

Conclusion

This will only be so until the enzyme denatures after its optimum temperature Since enzymes are catalysts for chemical reactions, enzyme reactions also tend to go faster with increasing temperature. However, if the temperature of an enzyme catalysed reaction is raised still further, an optimum is reached: above this point the kinetic energy of the enzyme and water molecules is so great that the structure of the enzyme molecules starts to be disrupted. The positive effect of speeding up the reaction is now more than offset by the negative effect of denaturing more and more enzyme molecules. Many proteins are denatured by temperatures around 40 - 50�C, but some are still active at 70 - 80�C, and a few withstand being boiled. So, my first prediction is that the enzyme will become denatured at around 40�C, and secondly, that as the temperature increases the reaction rate will increase by 50%, due to the molecules colliding together at a higher speed (kinetic theory) due to their extra energy obtained by the increase in temperature. My prediction is supported by Kinetic Theory in that if I apply twice as much heat there will be twice as much particle vibration therefore the reaction will happen twice as quickly. It is also backed by Collision Theory in that if I apply twice as much heat there will be twice as many collisions and therefore the rate of reaction will double. This will only be so until the enzyme denatures after its optimum temperature: 45�C. On the next page there is a graph of what I think the actual graph of the results is going to look. From the graph you can see that the maximum froth height rises until it reaches its optimum temperature (40 oc) then the graph starts to fall. Secondary source data In this experiment I intend to use at least 1 other piece of data to check my results against I am also going to use a set of results from a computer program called focus education software. In total I am using 3 sets of data including mine. ...read more.

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