Lesson Two White Bread Step One Lesson 2, White Bread, will focus on understanding yeast and how it makes dough rise. Yeast is a tiny one-celled plant, a microorganism, about the size of a human red blood cell. It may be hard to believe that this microorganism actually causes bread dough to rise, but it’s true. Yeast breaks down sugar into carbon dioxide and ethyl alcohol gases. In bread dough, the gases form bubbles, which honeycomb the mass of dough and puff it out until it rises. The equipment you will need: hand-held or stand mixer large mixing bowl liquid measuring cup dry measuring cup measuring spoons table knife to level off the dry ingredients in the measuring cup and spoons thermometer that will register 120º to 130ºF two 9- x 5-inch bread pans plastic wrap Click to go on the next step.