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To find out how temperature will affect the amount of carbon dioxide given off from yeast.

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Introduction

Biology Coursework Aim : To find out how temperature will affect the amount of carbon dioxide given off from yeast. Prediction : I predict that the cooler the water we use is, the less bubbles will be produced, if any at all. I think this because the warmer the water the molecules move faster/collide/react and more carbon dioxide will be given off from the yeast due to the enzymes respiring (fermentation). However I know that the enzymes that produce the carbon dioxide via fermentation will certainly denature after exposure to temperatures above that of 40oC. So I believe that anywhere between 20-40oC will produce a good amount of bubbles, less than 20oC will stop the enzymes from being able to produce carbon dioxide because they will simply stop. And above 40oC will more than likely denature the enzymes, resulting in no carbon dioxide bubbles being produced. ...read more.

Middle

Apparatus List : For the experiment, I will need : Bung Boiling Tube Clamp Stand Measuring Cylinder Smaller Test Tube Water Third Test Tube Fair Test : To make this a fair test, I will need to keep the same amount of water used in every experiment. The yeast will also be kept the same. I will use the same equipment every time I do an experiment in case yeast is left over in a measuring cylinder. Diagram : Method : 1. Set up all of the equipment as shown in the diagram 2. Measure 25cm3 of water, fill the boiling tube up 3. Measure 20cm3 of yeast, pour it into the smaller test tube 4. Heat the yeast to 20oC 5. Count the number of bubbles formed in the test tube linked to the yeast one. 6. Repeat steps 2-5 using different temperatures (40oC, 60oC, 80oC and 100oC) ...read more.

Conclusion

To avoid this problem I should have heated the water up before adding the dry yeast and sugar. We should have also mixed the yeast every time we took a sample. Maybe the main yeast cells had fallen to the bottom. If we shook the bottle the concentration would be equalled out instead of being at the bottom. Also temperatures above 50oC must have denatured the enzymes therefore we wouldn't have gained any bubbles from the yeast. To gain perfect results I could've averaged my results but unfortunately I got 0 bubbles from all 5 temperatures. I could have changed the water used in the boiling tube to a liquid which is less affected by temperature. I could also use an electric thermometer which would help me greatly as a manual thermometer isn't as accurate as an electric one would be. Finally I could have conducted another experiment to check if concentration of yeast affects the rate of which it respires. I could have kept the temperature at an optimal rate (40oC or so) and tried different concentrations of yeast ...read more.

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