Rising dough. Macrophotograph of bread dough in the process of rising during baking. Dough is a thick mixture of flour, Baker's yeast and other ingredients, used in the baking of bread, cake and pastry. Baker's yeast Saccharomyces cerevisiae is added to make the dough rise as it ferments sugar producing carbon dioxide in the process. This carbon dioxide gas produces air pockets in the dough, giving it a spongy appearance.