To discover which temperature gives the best condition for anaerobic respiration to occur in yeast.

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The Effect of Temperature on the Rate of Anaerobic


Respiration in Yeast


AIM: To discover which temperature gives the best condition for anaerobic respiration to occur in yeast.

EQUATION: For anaerobic respiration in yeast, the equation is:

Glucose (Enzyme-yeast) Alcohol + Carbon Dioxide + Energy

C6H1206 (Enzyme-yeast) 2 C2H5OH + 2 CO2 + 2ATP


PREDICTION:

There are several factors that could have been looked at to investigate the rate of anaerobic respiration in yeast:

Concentration of solution

Temperature of solution

Age and size of yeast particles

The chosen variable was temperature. By looking at an experiment where the effect of temperature on the enzyme Amylase was investigated, it is possible to predict that with a higher temperature, the enzyme (yeast in this case) will act faster. It acts faster as with more heat, more energy is produced, and with a greater amount of energy, the particles move faster and act more rapidly,
as heat is a form of energy. In the previous experiment it was concluded that when the mixture of Amylase and Starch was heated, the Amylase broke down the Starch more quickly that it did at room temperature. By looking at that experiments conclusions, it can be predicted that the warmer the Glucose and Yeast solution is, the faster the Yeast will break down the Glucose, therefore the more rapid the production of Carbon Dioxide bubbles will be, therefore showing that the higher the temperature, the faster the rate of Anaerobic Respiration will be in Yeast.

This is also due to the kinetic theory that with an increase in temperature, the rate of reactions will increase. This is due to the increase in the speed of the particles, which is brought about by the heat. Faster moving particles will bring about more collisions, which will mean that the reaction will take place faster. Because enzymes are sensitive to temperature changes, up until a certain temperature the amount of carbon dioxide and alcohol produced will increase. This amount will gradually increase with temperature until the shape of the active site is altered drastically and the lock and key hypothesis can no longer take place. This is called denaturisation, and when this happens no anaerobic respiration will occur.

Yeast is a single celled fungus made up mainly of protein, which has been used for its applications in fermentation. By secreting the enzyme zymase (a complex of 12 enzymes) in the yeast, carbon dioxide and alcohol are produced. This enzyme, zymase, acts on simple sugars such as glucose. Zymase (or usually any other enzyme), works by the ‘Lock and Key’ hypothesis, whereby the ‘key’ (the substrate substance) fits into the active site on the enzyme and they bind together. The reaction then takes place and the ‘key’ unlocks to form one or more new substances leaving the enzyme ready to perform the process again. The enzyme can only bind with the ‘key’ that fits the shape of the active site, which is unique to that type of enzyme. The zymase enzyme in yeast will only bind with a glucose molecule to produce the carbon dioxide and alcohol, which brings about the fermentation in the experiment I am going to do.

The perfect temperature for an enzyme to work in humans is at 37ºC; hence our body temperature is also 37ºC. If the temperature is too high, then the enzyme becomes denatured. This happens because the molecules of the enzyme vibrate so violently that they break their weak bonds holding the structure of the enzyme together. In a human it could be predicted that the most bubbles of Carbon Dioxide and therefore the most anaerobic respiration will occur when the water bath is at a temperature of 37ºC. However when producing alcohol in factories temperatures are much higher, and I predicted that as the temperature increases, so will the amount of anaerobic respiration, up until a certain high temperature when the enzyme becomes denatured. As the temperature decreases from this degree I predict that the rate of anaerobic respiration will decrease and less Carbon Dioxide bubbles will be produced. When the enzyme becomes denatured, the production of any bubbles of Carbon Dioxide will be impeded, and any anaerobic respiration occurring will be prevented.



EQUIPMENT:

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Yeast & Glucose solution
10 ml Syringe
Ice Cream Tubs filled with equal amounts of water - X4
Stopclock



METHOD:

1. Four ice cream tubs are filled with equal measurements of water.

2. The first of these tubs is cooled using ice and is set to 12ºC. The second left at room temperature (around 24ºC), the third heated to body temperature at 37ºC, and the fourth heated to 65ºC.

3. The syringe is filled with 10ml of glucose and yeast solution.

4. The syringe is then placed into the first ice cream tub and immediately a timer is set ...

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