Nature uses the same chemical reaction for fermenting grape juice to wine, for making bread dough rise, and for converting blood sugar into muscular energy. Each mol (180 g) of glucose (grape or blood sugar) is transformed into two mols of ethanol (ethyl alcohol) and two mols of carbon dioxide gas, while 109 kilojoules of energy is produced.
The tiny amounts of catalyst (enzyme) needed to make the reaction go are present in both yeast and muscle.
In potatoes and cereals hundreds of glucose molecules are linked together, by bonds with alpha configuration, into long-chain molecules of starch.
If you chew bread slowly, paying attention to the taste, you will find it gets sweeter the longer you chew. This is because the enzyme amylase in saliva releases the sweet sugars glucose and maltose by breaking the alpha bonds in the wheat starch.
Maltose is converted to glucose in the intestine and all the glucose then passes into the bloodstream to make up about 0.1% of the blood.
Glucose is sold in food stores as a colorless syrup made from corn-starch.
To carry out starch digestion and glucose fermentation cut a four-egg-cup tray from the bottom of a plastic egg carton. In cup one put one tsp. (5 mL) of warm water, 1/2 tsp. of cornstarch, and 1/2 tsp. of saliva.
In cup two put one and a half tsp. of warm water and 1/2 tsp. of corn-starch.
In cup three put one and one half tsp. of warm water and 1/2 tsp. of corn syrup.
In cup four put 2 tsp. of warm water.
You can judge the temperature in all of the cups by dipping your finger into cup four.
Stir each cup with its own toothpick and keep the cups at close to body temperature (37 degrees C) , where enzymes work best, by floating the tray in hot water.
After 30 minutes of digestion, add 1/4 tsp. of baker's yeast to each cup and stir. After about another 30 minutes of fermentation, when the yeast plants have grown, you will see bubbles rise and smell the "yeasty" odor of fresh bread in cups 1 and 3.
The bubbles are the carbon dioxide we breathe out, that makes bread rise and puts the froth on beer and the bubbles in champagne. No bubbles or odor should come from cups 2 and 4.
About one half of the dry weight of plants is glucose molecules linked together with bonds of beta configuration into long-chain cellulose molecules. Only bacteria can break these beta bonds and this is why people cannot live on paper, straw or wood.

From Do-It-Yourself Chemistry
by Doug Hayward, University of British Columbia, 1988