How does yeast make dough bread rise?
Yeast is a one-celled non-green plant. When put into bread dough it eats the sugar and digests it and gives off CO2 gas which causes the bread to rise. It also gives off alcohol which is evaporated when the bread bakes. The gas bubbles expand the gluten protein in the dough. In baking the gas expands more as the dough is heated.