Cellular Respiration Lab-4-2

Biology Lab: Yeast Air Balloons Pictures are required and do not walk away while the experiment is going on because the balloon might burst and spread the contents all over your kitchen The purpose of any leavener is to produce the gas that makes bread rise. Yeast does this by feeding on the sugars in flour, and expelling carbon dioxide in the process. While there are about 160 known species of yeast, Saccharomyces cerevisiae, commonly known as baker's yeast, is the one most often used in the kitchen. Yeast is tiny: Just one gram holds about 25 billion cells. That amount of fungi can churn out a significant amount of carbon dioxide, provided it has the simple sugars it uses as food. Fortunately, yeast can use its own enzymes to break down more complex sugars—like the granulated sugar in the activity below—into a form that it can consume. Make a yeast-air balloon to get a better idea of what yeast can do. What Do I Need? What Do I Do? 1. Stretch out the balloon by blowing it up repeatedly, and then lay it aside. 2. Add the packet of yeast and the sugar to the cup of warm water and stir. (Make sure that you divide the yeast into 4 equal parts). Conduct the experiment using warm water, yeast and sugar, cold water, yeast and sugar, warm water, yeast and no sugar, cold water and yeast with no sugar. 3. Once the yeast and sugar have dissolved, pour the mixture into the bottle. You’ll notice the water bubbling as the yeast produces carbon dioxide. 4. Attach the balloon to the mouth of the bottle, and set both aside. 5. After several minutes, you’ll notice the balloon standing upright. If you don’t see anything happen, keep waiting. Eventually, the balloon will inflate. What's Going On? Please tell me what you think is happening. What gas is filling up the balloon? The yeast is feeding on the sugar and producing carbon dioxide as it breaks down the sugar. The carbon dioxide gas builds up inside and fills the balloon, which causes it to inflate. Additional things to do for this lab Also, try the same experiment using hotter and colder water. Use a thermometer to measure the temperature of the water. At what temperature is the yeast most active? The yeast is more active in warm water. At what temperatures is it unable to blow up the balloon? Colder water