When wheat flour is mixed with water and stirred or kneaded, the gultenin and gliadin proteins not only bond with the water but also link and crosslink with one another to eventually from sheets of a flexible, resilient film called gluten. Gluten can trap air and gases formed by yeast, causing bread to rise. As the yeasts feed on the sugars, they produce a liquid containing both alcohol and carbon dioxide. The carbon dioxide is released upon contract into the air bubbles, enlarging them. In baking, the alcohol converts to gas, enlarging the bubble even more-producing oven spring. Flexible starch granules held in place by the gluten network also bend around the air bubble. The gluten protein eventually cooks, releases its water into the starch, and begins to firm. This provides the structural framework for the loaf of bread. As the starch gelatinizes, it also becomes semi-rigid, giving even more support. In cake or quick breads, however, too much gluten can be detrimental. The efficacy of the chemical leaveners can be compromised when gluten prevents them from bubbling through a batter. Protein content determines how much water a flour can absorb-the greater the amount of protein, the more hydration is possible.