Investigation of the effect of temperature on the rate of respiration of yeast.

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Investigation of the effect of temperature on the rate of respiration of yeast


The aim of this investigation is to determine the effect of temperature on the rate of respiration of yeast. The temperatures at which the culture was tested at were 20°C, 30°C and 40°C to give a range of rates of respiration which can be compared. The yeast cultures were maintained at these temperatures using a water bath as water has a high specific heat capacity and thus maintains a specific temperature relatively well.

As a result of preliminary studies into the topic, the hypothesis was made that ‘as the temperature increased, the rate of respiration would also increase in the yeast.’ This is because the reactions that occur in respiration are enzyme catalysed. Therefore, we can deduce that any reaction where enzymes are present will have an optimum temperature at which the rate will be at its optimum. This is likely to be around the 30°C - 40°C.

For example at the very first step of respiration in glycolysis, the enzyme phosphofructokinase is used to phosporylate the glucose so that it can be split into to two triose sugars that will eventually produce a pyruvate molecule each. When these pyruvate molecules enter the Kreb Cycle and is converted to acetate, coenzyme A combines with this new compound to assist in the formation of oxaloacetate. Decarboxlases and dehydrogenases are also used in the  Kreb Cycle. Then in the last stage of oxidative phosphorylation cytochrome reductase and cytochrome oxidase are used. Thus, as a result of all these enzyme catalysed reactions, the temperature will be a limiting factor and from prior knowledge it is assumed that these enzymes work best around 30°C – 40°C.

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When we increase the temperature of a reaction the Rate of product formation increases. From a thermodynamic view increasing the temperature increases the average kinetic energy of the reactant molecules. According to the Collisional Theory, this increases the impact energy upon collision which increases the probability that more molecules will exceed the Activation Energy producing more product at an increased rate. How is this accomplished if concentrations are not altered? According to the Rate Law the only thing that would affect the Rate other than concentrations of reactants is to affect the rate constant itself. Svante Arrhenius investigated the relationship ...

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