Question

What happens when yeast is added to the dough?

Answer 1

Fermentation takes place in yeast cells, bacteria, and mammalian muscles. The mechanism that breaks down glucose is anaerobic.
The breathing that occurs at the cellular level in our bodies is referred to as cellular respiration. It can happen when there isn't enough oxygen or when there isn't enough. Glycolysis is the first step in any sort of cellular respiration, and the final product is pyruvic acid, a $3$-carbon molecule.
The pyruvic acid generated by partial oxidation of glucose is transformed to ethanol and carbon dioxide in organisms like yeast $\left( {C{O_2}} \right)$. Alcoholic or ethanol fermentation is the name for this anaerobic situation. The enzymes pyruvic acid decarboxylase and alcohol dehydrogenase catalyse the entire reaction.

Complete answer:
Large starch molecules break down into simple sugars as soon as these components are mixed together, thanks to enzymes in the yeast and wheat. The yeast breaks down these basic carbohydrates and produces a liquid that releases carbon dioxide and ethyl alcohol into the dough's existing air bubbles.
The sugar in the dough is converted to carbon dioxide gas and ethanol by the yeast (alcohol).
The trapped gas causes the dough to rise, while the alcohol created during the fermentation process evaporates during baking.
Fermentation, the mysterious process that transforms a dense ball of dough into a well-risen loaf of bread, is powered by yeast.
If the dough contains a strong and elastic gluten network, the carbon dioxide will be trapped within the bubble and begin to expand it, similar to how bubblegum gets inflated. The dough rises as more and more microscopic air cells fill with carbon dioxide.

Note:
Big molecules in proteins, carbohydrates, and fats have little flavour, but when they break down into their building blocks—proteins into amino acids, starches into sugars, or lipids into free fatty acids—they all have wonderful flavours, as Harold McGee has pointed out. Fermentation breaks down huge molecules into smaller, tasty ones, whether it's working on fruit juices to generate wine or flour to make bread.
At the start of fermentation, enzymes in the yeast begin to break down starch into more palatable sugars. The yeast consumes these sugars, as well as sugars already present in the dough, and generates a variety of delicious byproducts, including organic acids and amino acids, in addition to carbon dioxide and alcohol.