A. Gluten is a protein that, when mixed in dough, allows the dough to become very stretchy or elastic. When the yeast mixes with sugar, it releases carbon dioxide. This is what makes the tiny bubbles in bread. The kneading makes the dough more elastic. It rises and makes a lighter, fluffier loaf.
Sugar is an absolutely necessary ingredient in the chemical reaction of baking.
Without the sugar, the yeast will not generate the gas necessary to make the bread rise. You can use sugar, brown sugar, honey, molasses, or whatever your recipe requires. The chemical reaction with the yeast will be the same, but the different forms of sugar will cause your bread to have different flavors and textures. We don't recommend using a salt substitute. The salt in a bread recipe is a necessary ingredient, as it controls the chemical reaction of the yeast and sugar.