1. She blinded me with science … and then made yeast bread.
Yeast Breads Notes
No. 2

2. Types of Flours
Bread Flour – high protein, best for yeast breads. Generally milled in the North. Highest gluten content. Use of bread flour means your dough will require a second rise.
All-purpose flour – middle protein content, O.K. for bread, O.K. for cake, biscuits and muffins. A flour that is for all purposes.
Cake Flour – low protein content. Generally milled in the South. Good for very tender baked goods, like cake, biscuits and muffins.

3. Chemical Leaveners
Chemical leaveners (Baking powder and baking soda) work by producing gas which makes baked goods rise.
Baking powder (often sold as Double Acting) releases the most gas when it is heated. Baking powder is baking soda with the addition of a dry acid like Cream of Tartar.
If you have no baking powder, you can substitute. 1 teaspoon baking powder is replaced by 1/4 teaspoon baking soda and 1/2 teaspoon cream of tartar.

4. Now for the science part …
Bread is actually a combination of ingredients, science and heat.
When yeast grows in bread dough, it produces two waste products – alcohol and carbon dioxide gas.
The carbon dioxide gas bubbles make yeast bread rise.
You punch down the dough and let the gas escape. Then you let the dough rise again. This process improves the flavor of your finished product. The punch down also redistributes the yeast to new food sources, so it can continue to grow.