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Find the effect of temperature on anaerobic respiration of yeast.

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Introduction

Introduction We wanted to find the effect of temperature on anaerobic respiration of yeast. We investigated how a mixture of yeast, water, sugar, and flour were affected. Diagram Apparatus 1g of yeast 0.5g of sugar 10g of flour 6 measuring cylinders - to put the sachets in and the 20cm3 of water Measuring cylinders to measure the water Thermometers - to keep the same temperature in the water baths Water baths - at 20�C, 30�C, 40�C, 50�C, 60�C Hot air oven - at 70�C Beakers - to use to put the yeast mixture in the cylinders. Method We set up the apparatus as shown, and placed 1g of yeast, 0.5g of sugar, and 10g of flour each into the beakers. Then we added 20cm3 of water, measured with a measuring cylinder, and stirred the mixture until there were no bubbles left in it, and it was a smooth paste. Then the volume of the dough in each was 25cm3 and we poured it into 6 measuring cylinders. Then we placed the 4 cylinders in 10�C, 30�C, 40�C, 50�C and 60�C in water baths at those constant temperatures, maintained with a thermometer. Then we left a cylinder at room temperature (20�C) and the last in a hot air oven at 70�C. ...read more.

Middle

A chemical reaction always involves a substrate changing into another. The substance, which is present in the beginning of the reaction, is called the substrate. The substance, which is made by the reaction, is the product, e.g. ethanol + CO2 from glucose and yeast. Enzymes have a very precise 3D shape, and each has a "duct" and has exactly the right size and shape for a molecule of the enzyme's substrate to fit into it. This "duct" is known as the active site. When the substrate slots into the active site, the enzyme "tweaks" the substrate molecule, by pulling it out of shape and making it split into product molecules. These then depart from the active sit, which is then ready to repeat the process with another substrate molecule. Most chemical reactions happen faster when the temperature is higher. At higher temperatures, molecules move around faster. This makes it easier for them to react together. Usually a rise of 10�C will double the rate of the reaction. They are very sensitive to high temperatures. Once the temperature is above 100�C, the enzyme will be damaged. When this occurs, it cannot catalyze its reaction so well, so the reaction slows down. The water rehydrated the powdered yeast, sugar, and flour mixture, so it gave the enzymes a solution to work in. ...read more.

Conclusion

These are due to the problem we had with the uneven temperatures, in which the measuring cylinders with dough were in, as it was relatively difficult to maintain the temperatures in the water baths, as we continuously had to put some hotter or colder water into the baths. However, the results were reliable and accurate to support the conclusion, which also agreed with my hypothesis. As the temperature increased, the volume of the dough increased until it reached its peak, and the enzymes had reached their optimum temperature. Then the volume decreased because the enzymes were denatured. I hav creatd another experiment which investigates the best temperatures at which yeast enzymes work best at. I want to investigate further into what exactly is the yeast enzymes' optimum temperature, as it was 101cm3 at 50C, but as I mentioned before - the dough was at unevern temperatures, as it was hard to control it without the special abilities of laboratory machines. I know that the optimum temperature is between 40C and 50C. Method We will mix 1g of yeast, 0.5g of sugar, and 10g of flour, each in 4 beakers with 20cm3 of water, which will be measured with a measuring cylinder. Then we will pour it into measuring cylinders, but this time using a measuring cylinder with a larger opening, to avoid spilling the mixture around the edges of it. Then, the volumes in each of the 4 cylinders will be 25cm3 ...read more.

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