When the dough is hydrated, glutenin and gliadin, two naturally occurring proteins in flour become flexible and start to interact with each other. They stick together and form bonds called cross-links The chemical cross linking forms gluten. Gluten, a water-insoluble protein is very elastic and stretchable substance which gives structure to the bread. The more water is added to an extent, the stronger and more extensive gluten strands are formed. The more cross-links are formed, the more ability of gluten to support gas bubbles and starch granules as the dough rises and bakes.