Fermentation Is a Metabolic Process

Fermentation is a metabolic process that converts sugars into acids, gases and or alcohols. There are two different types of fermentation, lactic and alcoholic. The fermentation that was used in this experiment was alcoholic fermentation. Yeast is a eukaryotic unicellular microorganism that will convert grape juice into alcohol, by the process fermentation.

The purpose of the experiment was to investigate the effect of temperature on the rate of anaerobic respiration in yeast. It was presumed that if the temperature of the yeast and the substrate was warmed, than the rate of respiration would be greater.

One test tube, filled with 3 grams of yeast and 20 mL of grape juice, was placed in a beaker of room temperature water while the other test tube of 3 grams of yeast and 20 mL of grape juice was placed in a beaker of 40 degree Celsius water. The test tubes were left in the beakers of water for five minutes before they were connected to the delivery tube. A graduated cylinder that was filled with water and no air bubbles was held by a ring clamp and was then submerged into a water trough. A delivery tube connected the yeast and grape juice to the graduated cylinder. After five minutes, the amount of carbon dioxide produced from the fermentation process was measured and recorded.

The independent variable in this experiment was the temperature of the fermentation system. The dependent variable was the volume of carbon dioxide produced. The volume differed depending on the temperature. The variables that were kept constant in both experiments were the wait time, the volume of grape juice, the mass of yeast and the time taken to collect gas. With these variables kept constant, the only difference between both setups was the temperature of the test tubes.

For the test tube in 40 degrees Celsius water, 33 mL of carbon dioxide were produced. This was seen in the amount of water displaced in the graduated cylinder. For the test tube at room

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