Yeast Respiration Lab Report

Before the experiment, we made some hypotheses based on predictions questions. First, yeast will metabolize sugar and produce a gas. This is because yeast is a living organism and all living organisms like yeast must use energy (such as sugar) to obtain energy. Yeast will metabolize sugar and gives off carbon dioxide as a by-product. For the second hypothesis, we were expecting that yeast will produce a gas when sugar is available. For the third hypothesis, we did not expect yeast to produce a gas when no sugar or other food is available. The reason is that carbon dioxide is a product of respiration and is formed when the yeast respires. Therefore, when no food and sugar is available, respiration cannot take place. Hence, no carbon dioxide is formed.
In the test tube 4, 5, 6 that contained yeasts and water only, the yeast did not have food which was sugar. That was the reason why test tube 4, 5 and 6 did not expand. In the test tube 1, 2, 3 which contain yeast, water, and sugar, the yeast should have thrived and made a lot of carbon dioxide, so that the balloon expand bigger and bigger
The reason we use three test tubes with yeast, sugar, and water and three test tubes with just yeast and water, instead of only one test tube with each type of mixture is because we had to compare the difference in size between each balloon and clarify that each of the test tubes that contain sugar will expand.
In this experiment, we had grown yeast in the test tube filled with water and sealed with a balloon. These growth conditions were considered as anaerobic because they were sealed and the amount of oxygen in the test tube will be reduced in a short time. Thus, these yeasts will carry out anaerobic