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Enzymes - complex three-dimensional globular proteins, with hydrophillic side chains which makes them soluble

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Introduction

Enzyme Coursework Introduction Enzymes are complex three-dimensional globular proteins, with hydrophillic side chains which makes them soluble. The enzyme molecule is normally larger than the molecule of the substrate it acts upon, but only a small part comes into contact with the substrate. This region is called the active site so the substrate of the enzyme can bind to it. The active site has such a shape that it allows the substrate to fit perfectly, and to be held in place by temporary bonds. The bonds form between the substrate and some of the R- groups of the enzymes amino acids. Enzymes are very specific because the enzyme has a particular shape into which the substrate fit perfectly. This is known as the 'lock and key' hypothesis where the substrate is the key whose shape is complementary to the enzyme or lock. Fig.1 Fig.1 shows that when a substrate complex is formed it is 'activated' into forming the products of the reaction. Once formed, the products no longer fit into the active site and escape into the surrounding medium, leaving the active site and escape into the surrounding medium, leaving the active site free to receive further substrate molecules. Enzymes are biological catalysts, each enzyme is specific to a particular reaction or group of similar reactions. Catalyst is a substance that alters the rate of reaction but remains chemically unchanged at the end of the reaction. Catalysts speed up reactions. They do this by providing an alternative pathway for the reaction. ...read more.

Middle

intervals add 1 drop of reaction mixture to the iodine > Note change > Repeat for other temperatures Substrate Concentration > Mix 5cm3 of 1% starch suspension in buffer pH 7 with the same volume of 0.1% amylase, also made up in the same buffer. > Set up a control containing 5cm3 of buffer only instead of amylase. > Set up a second control containing 5cm3 of boiled amylase only. > Incubate the tubes at 37oC. > At 30 second intervals, remove drops of the reaction mixture and place in a well tray. > Add drops of iodine in iodine solution. > Note the colour change. > Note the time taken for the blue-black colouration to fail to appear. Enzyme Concentration > Mix 5cm3 of 1% starch suspension in buffer pH 7 with the same volume of 0.1% amylase, also made up in the same buffer. > Set up a control containing 5cm3 of buffer only instead of amylase. > Set up a second control containing 5cm3 of boiled amylase only. > Incubate the tubes at 37oC. > At 30 second intervals, remove drops of the reaction mixture and place in a well tray. > Add drops of iodine in iodine solution. > Note the colour change. > Note the time taken for the blue-black colouration to fail to appear. During the experiment try and measure out the chemicals as carefully as you can and try keeping the time as close to 30 seconds if not exactly. ...read more.

Conclusion

> The time at which the iodine drops were dropped at may have been to early or too late. To improve this I would drop the iodine solution exactly at the 30 second intervals. > Another reason may be that as the test tubes were taken out of the water bath the temperature may have decreased while putting the iodine drops in. > Also the test tubes were to remain in the water bath for 5 minutes but they may have been taken out too early or too late. To improve this I would take the tubes out exactly at 5 minutes. If I were to do this investigation further then I would do the following experiment: Experiment to test the hypothesis that catalase (in yeast) breaks down hydrogen peroxide 1. Half fill the beaker with tap water and use water bath with the Bunsen burner. 2. Place approximately, half the yeast-glucose mixture into the boiling tube and leave in the water bath for 5 minutes. 3. Use the spirit marker to label one test-tube A and the other B. 4. Place the test tubes in the test-tube rack. 5. Wearing safety glasses and gloves, pipette 5cm3 hydrogen peroxide into tubes A and B. 6. Cool the boiled yeast-glucose solution. 7. Using a clean pipette, place 5cm3 of the cooled yeast solution into tube A. 8. Place 5cm3 of the unboiled yeast mixture into tube B. 9. Start the clock immediately 10. At 2minute intervals, use the ruler to measure the height of the froth (In mm) which may appear above the liquid in each tube. 11. Record the data in the table. ...read more.

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