What factors could have an effect on the rate of respiration in yeast?

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What factors could have an effect on the rate of respiration in yeast?

There are many factors that could affect the rate of respiration in yeast. Such as the temperature the yeast respires at as at different temperatures the enzymes in yeast work faster or slower at breaking down the glucose this is because the yeast enzymes will have more or less energy with which to break down the glucose. The amount of yeast will also have an effect on the results, as if we are to use different amounts in each experiment it will form an unfair test. Another factor that could affect our investigation is the percentage of glucose in the yeast. I must also make sure to leave all experiments undisturbed during the course of respiring, this means they cannot be stirred or let air get to them.

I have chosen to investigate the affect the percentage of glucose concentration has on the rate of respiration in yeast. I will use an experiment to determine whether the yeast’s rate of respiration will be quicker, slower or if it does not change when the percentage of glucose concentration in it is varied.

I predict that the yeast’s respiratory rate should increase in speed as the percentage of glucose increases. However this may at some point peak and therefore cease to increase in speed, one point of this investigation is to find the optimum percentage of glucose concentration to give the optimum rate of reaction.

My reason for the above prediction is that yeast is a unicellular fungus, which feeds saprophytically and can respire both aerobically and anaerobically. In the experiment the yeast will be respiring anaerobically and breaking down the glucose stored in it as a waste product of this process it will also form CO2 and alcohol in the form of ethanol. This respiration process is called fermentation. The yeast breaks down the glucose using a series of enzymes.
I deduce from this that the more glucose that is present in the yeast the more will be broken down and therefore more CO2 and ethanol will be produced as waste products at a faster rate.

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Prior to this investigation I carried out a shorter experiment of the same kind but just using percentage of glucose concentrations of three and five- percent. Although this was a very basic experiment I found that the five- percent concentration was quicker at producing 2ml of CO2 than the three- percent concentration. In this experiment I used 5 grams of yeast in both concentrations.

The basic method for my experiment is as follows:
1 I will change the percentage of glucose concentration in the yeast.
2 I will measure the rate of reaction (time taken) for the yeast to produce 2ml of ...

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