Biology: The Production of CO2 by Yeast

In this experiment, we investigated whether or not different wavelengths of light affected the rate of anaerobic respiration. It is a well-known fact that different wavelengths of light affect the rate of photosynthesis as lights aerobically respire, which then led us to the above question. As seen in the results obtained, whilst exposing the yeast and sugar solution to different wavelengths of light, there was no change in the amount of carbon dioxide produced. When the yeast and sugar solution was exposed to normal light and ultraviolet light, 15 cm³ of carbon dioxide was evolved. Hence, it can be concluded that different wavelengths of light have no effect on anaerobic respiration.

As stated earlier, we investigated the effect of different wavelengths of light on anaerobic respiration, and in effect we were also investigating the effect of heat energy on anaerobic respiration. Throughout the trials, we noted the temperature change to see if a change in temperature had any bearing on the results. When the yeast and sugar solution was exposed to visible light and ultraviolet, a similar change in temperature was noted which gave rise to similar results. However, when the yeast and sugar solution was exposed to infra-red light, there was a significant increase in the environment temperature (after 10 minutes, the temperature had reached in excess of 100 degrees Celsius). After this trial, the yeast and sugar solution had become a thicky paste, which then led us to believe that the enzymes had become denatured, which would explain why no carbon dioxide was produced. Enzymes are biological catalysts which are temperature, pH and substrate sensitive which can be seen in the diagram below:

Upon further investigation, we discovered that yeast’s optimum temperature was 25 degrees Celsius and because we were conducting the experiment in a room whose temperature was set at 22 degrees Celsius, the rate of the reaction would be less than the optimum rate of reaction. However, it could also be inferred from this that infrared energy would result in the greatest production of carbon dioxide as the yeast’s environmental temperature would be closer to that of its optimum. However, as stated earlier, over the duration of the trial (10 minutes) temperatures reached 100 degrees which was significantly higher than yeast’s optimum temperature which led to the denaturation of yeast and because of the permanent change in its structure, the yeast was unable to react witht eh sugar solution and so no carbon dioxide was produced.