How does bread dough rise when you add yeast?

When you add yeast to bread dough, the yeast organisms consume sugars present in the flour and produce carbon dioxide gas and alcohol as byproducts through a process called fermentation. The carbon dioxide gets trapped within the gluten network, which is the elastic protein structure that forms when flour proteins combine with water during kneading. As fermentation continues, more gas bubbles accumulate and expand, causing the dough to increase in volume. The gluten network is essential because it acts like a stretchy web that holds the gas in place rather than letting it escape. When the bread is baked, the heat kills the yeast, the alcohol evaporates, and the gluten structure sets permanently, giving the bread its light, airy texture.