Well Yeast eats, just like us. They eat sugar. Just like us they build up gas and release as what we call methane (aka commonly known as farting,medical term flatulence)
The sugar they eat builds gas up and releases it as Carbon Dioxide.
Yeast release carbon dioxide to make bread rise.
Yeast are tiny animals. When they eat, they release carbon dioxide. That "inflates" the dough.
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Yes Yeast converts or "feeds" on the carbohydrates that flour and sugar provide into carbon dioxide gas. This process allows your bread to rise
Mixing carbon dioxide with yeast to create fermentation is reversible in the sense that the process can be stopped and the components (yeast and carbon dioxide) can be separated. However, once the yeast consumes the sugars and produces the carbon dioxide, this chemical reaction cannot be undone to revert back to the original state.
When glucose is added to yeast in solution, the enzymes inside it turn the mixture into ethanol and carbon dioxide, so, for your question, carbon dioxide. It also respires normally (aerobically) and then too produces carbon dioxide.
Yeast produces CO2 gas and sometimes ethenol when it metabolizes sugar.
Carbon dioxide
The ingredient in bread that produces carbon dioxide is yeast.
Carbon Dioxide and Alcohol (anaerobic respiration)
Yeast will respire the sugar causing the yeast to give off Carbon Dioxide.
The gas produced by baking bread is called Ozone. It is a poisonous gas, if a lot is inhaled, but the little bit made when bread is baked is not harmful.