The Rate Of Respiration In Yeast And

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The Rate Of Respiration In Yeast And How It Is Affected By Temperature. Essay, Research Paper Harry Fox 11ST Biology Science 1 – Strand 1: Planning Aim??????????? In my experiment, my aim is to find out any correlation between rate of respiration? of glucose by yeast and the mixture?s temperature. I shall do this by conducting an experiment which will involve the timing of the yeast, water and glucose which has been mixed with a little methylene blue. I shall time how long it takes to revert to the original colour using a control. This shall be done at various temperatures. To obtain the best range of values to use in my final experiment, I shall conduct a preliminary experiment. This will also aid accuracy of the final experiment by uncovering potential flaws in the

method.Hypothesis and Theory ??????????? There are many ideas to suggest that the change in temperature will cause an increase of respiration in yeast. Yeast is a single celled fungus made up mostly of protein which has been used for its applications in fermentation. Yeast, after activation creates the ferments carbon dioxide and ethyl alcohol by secreting the enzyme zymase (a complex of 12 enzymes) in the yeast which acts on simple sugars such as glucose. The alcohol produced has been used in making wines and beers and the carbon dioxide produced has been used in baking as it gets trapped in the dough and causes it to rise. ??????????? Enzymes are catalysts which speed up reactions, they are made from protein and are specific as to which substrate they work on. Enzymes basically

work due to the ?lock and key? theory, where the substrate substance (the ?key?) ?fits? into the active site on the enzyme and they bind together, the reaction takes place and the substrate unlocks to form one or more new substances leaving the enzyme ready to perform the binding again. An enzyme can only bind with a substrate that fits the shape of the active site unique to that kind of enzyme. A zymase-complex enzyme will only bind with a glucose molecule to produce the ferments carbon dioxide and alcohol which brings about the fermentation in my experiment. This ties in with the Induced Fit theory which states that the substrate cannot bring about catalysis and the reaction itself, but the active site, when it comes in to contact with the substrate slightly changes its shape

to form an effective fit and arrangement of catalytic groups on its surface which brings about the catalysis reaction. To display this, think of a hand in a glove where the hand acts as the key and substrate, inducing a change? in the shape of the glove which acts as the enzyme. When some substrate substances induce a fit with the enzyme, the enzyme may not be able to ?accept? some other substrate(s). These ideas tie in with my experiment to explain the formation of the products of respiration of yeast. ??????????? Yeast have to make energy, stored as ATP to carry out all cellular functions. To do this they can respire both aerobically when there is plenty of oxygen, but where oxygen is short, they respire anaerobically; by this, they are called partial anaerobes. This produces

less energy, but keeps the yeast alive. Pyruvic acid has to be broken down in respiration when formed by breaking down of glucose molecules, this can?t be done in the same way as it is aerobically when respiring anaerobically which is how the carbon dioxide and ethanol is formed through the zymase. Here is the equation for anaerobic respiration:??????????? ????? enzymes in cytoplasm ??????????????? ????????? (zymase complex) glucose???? —————–>??? ethanol???? +??? carbon dioxide??? +energy C6H22O6???????? ????? ????????????????? 2C2H6OH?????? ???????? CO2??????????? 210 Kj/mole210Kj/mole in anaerobic respiration as aposed to 2890Kj/mole in aerobic respiration There is 2ATP from each respired glucose molecule – in aerobic there is 38ATP.??????????? Kinetic theory