Anaerobic Respiration of Yeast.

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Anaerobic Respiration of Yeast

Aim: To investigate the effect of temperature on anaerobic yeast respiration.

Basic outline plan: I plan to force a solution of yeast and glucose to anaerobicly respire. I plan to measure the gas collected at allotted intervals during a set period of time, when the solution is at different temperatures. I will need equipment to accurately measure the volume of gas collected, and an indicator to show me that all no oxygen is present in my solution. I will also need to make a way to force it to anaerobicly respire by creating an air tight layer over the top of the substance.

Prediction & Background information:

I predict that a gas will be given off and this gas will be CO2 as we are anaerobicly respiring yeast.

We know that Anaerobic Respiration In yeast has the following formula.

Glucose            Carbon Dioxide + Ethanol + Energy

C6H12O6              2CO2 + 2C2H5OH + 210 KJ/Mole.

 I predict that the volume of gas expelled will increase with temperature. I believe this for a few reasons. The first is due to the ‘Kinetic theory’, this states that the extent of a molecules movement depends on its state and temperature. As temperature increases, the particles become more ‘exited’, and so move around and collide and react more frequently and rapidly. It is these collisions which cause the reaction. We also know that heat is a catalyst in all reactions.

I also know that yeast is an enzyme and all enzymes have an optimal temperature at which they work best, this is around 45º for yeast.  However I predict that if the temperature is raised too much, then the reaction will not occur at all. I believe this because yeast is an enzyme, and according to the, ‘GCSE revision guide’ and the lock and key theory, enzymes are protein molecules, and each enzyme has a different shape for a certain reactant to fit into. This is called the active sight. But protein molecules and the active sight become denatured by extreme temperature of pH. When the protein is denatured this is irreversible and the mechanism no longer works. Most enzymes become denatured around 45º, but yeast is a little stronger and so should become denatured around 50º-60º. Therefore I believe that the amount of gas collected will increase over an allotted time, until the temperature becomes to high, and then their will be no reaction taking place at all.

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Also I did some preliminary work where we used Hydrogen Carbonate indicator to detect C02 by turning yellow, and during this experiment it was made clear that more bubbles were produced in an allotted time, and the indicator turned yellow quicker with hotter temperatures.

I think it will also be best to use the same yeast for each experiment before we make it denatured, to ensure that the concentration of glucose and yeast is constant. This will also be easier as after the oxygen has been removed for our solution, we will not have to do it again. ...

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