The Effects of Concentration of Sugar on the Respiration Rate of Yeast

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The Effects of Concentration of Sugar on the Respiration Rate of Yeast Investigating the effect of concentration of sugar on the respiration rate of yeast We did an investigation to find how different concentrations of sugar effect the respiration rate of yeast and which type of concentration works best. Respiration is not breathing in and out; it is the breakdown of glucose to make energy using oxygen. Every living cell in every living organism uses respiration to make energy all the time. Plants respire (as well as photosynthesise) to release energy for growth, active uptake, etc…. They can also respire anaerobically (without oxygen) to produce ethanol and carbon dioxide as by-products. This reaction is shown in the equation: Glucose Ethanol + Carbon Dioxide + Energy C6H12O6 2C2H5OH + 2CO2 Anaerobic respiration by yeast is generally called fermentation. Yeast is a living organism that produces enzymes. These enzymes break down glucose (by colliding with each other) to be able to respire anaerobically. I predict that the rate of fermentation will increase proportionally as the concentration of sugar increases but only up to a certain point were it will begin to decrease and eventually stop. I believe this because the more sugar added to the yeast the more glucose broken down producing ethanol and carbon dioxide. The rate of carbon dioxide produced in a minute will also increase because the higher the concentration of sugar the more heat energy produced and so the more the molecules will move around and collide. Also the higher quantity of glucose molecules the higher chance of them colliding with the enzymes. I believe the reaction will slow down and eventually stop when the sugar reaches a certain concentration because the yeast will be killed by either: 1. The high concentration of ethanol produced as a by-product. 2. The temperature of the reaction, as some of the energy produced converts into heat energy. At really high temperatures the reaction will stop because the heat will have denatured the enzymes.

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