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The Effect Of Temperature On Anaerobic Respiration In Yeast

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GCSE Biology Coursework The Effect Of Temperature On Anaerobic Respiration In Yeast Enzymes Enzymes are the tools of life. They do almost everything in a cell. Virtually every one of life's chemical reactions is driven by some enzyme. Enzymes are organic catalysts that work like a starter on a car. With a small input of energy from the starter, a car can run on its own energy all day. They don't get not used up or changed when they "jumpstart" another molecule. They can perform the same task over and over working very fast. They can carry out their task thousands of times per second. Each enzyme has its own unique structural shape that allows it to bind to or "unlock" certain other molecules called substrates. When the correct "lock" and "key" come together, a chemical bond is formed. Lock and Key Theory The lock and key structure is a theory on why enzymes catalyse reactions. This theory states that all enzymes and substrates (the object which the enzyme act on) have specified structures (active site) and chemical properties. The substrate fits into the enzyme's active site, and they react. The substrate is broken down, and then the enzyme can act on the next substrate. This can be done as quickly as 32 million particles per second. This means that, like only a certain and correctly sized and shaped key can fit into a certain lock, only a certain substrate (key) ...read more.


Diagram: Method: 1. Using a beaker I set up a water bath at 30�C. 2. I then poured 20cm� of the yeast solution into a small conical flask and added 2 drops of diazine green. 3. I then added enough liquid paraffin to create a layer on top of the yeast. 4. I submerged the conical flask in the water bath at 30�C. 5. I then waited for the indicator to turn pink. 6. Once Pink I put a rubber bung with a tube connected to a gas syringe in the top of the conical flask. 7. Once I had put on the rubber bung, I started the stopwatch and took a reading of the volume of CO2 produced every 5 minutes for 15 minutes. 8. Using the same yeast I repeated this experiment at 40�C, 45�C, 50�C and 60�C. 9. I recorded my results in a table with the average volume of gas at each temperature. Results: Analysis: From looking at the graph from these results you can clearly see that as the temperature rises from 30�C to 50�C, the rate of reaction and the volume of gas produced through anaerobic respiration also rise. This is due to the Kinetic Theory. As the yeasts temperature rises, the molecules gain more kinetic energy and begin to move at much greater speeds. This causes the enzymes to collide with the substrates much more frequently, meaning many more keys will find there locks, which in turn causes more products to be formed. ...read more.


However my final reading at 15 minutes was far lower than the other two. Only 17 cm� compared with 42cm� and 33cm�. I am certain that this is due to the enzymes denaturing. I must have added too much hot water to the water bath, causing the temperature to rise above 50�C and denature the enzymes causing them to work much less effectively. You can see this result as the red circled one in my results table. I decided not to use it in the average for 50�C as it was an anomaly that would have drastically changed the average and shape of my graph. There is not a great deal I could have done to improve my experiment. I could have been a slightly more careful when adding hot or cold water, as this seemed to be the cause of my two anomaly's. I also could have used a burette instead of a gas syringe in order to get more accurate readings. Also it may have been useful to get results at more temperatures and also take more repeats in order to make the averages more accurate. This would also make it much far easier to identify any anomalies. Improved Experiment Diagram: Despite the various ways in which I could improve my experiment, I still can depend on my results. I got the data I set out to get and achieved my aim. Even though I got two anomalies' I managed to spot them and exclude them from the experiment, giving me sufficient, good quality data that allowed me to draw a firm conclusion. ?? ?? ?? ?? ...read more.

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