Yeast Fermentation Causes Dough to Rise

Steps:

• Yeast ferments sugars in dough, producing gases and other byproducts.
• The diagram likely shows one container with risen or bubbly dough (X) and the other unchanged (Y).
• This difference results from gas trapping in the dough, increasing volume.
• Carbon dioxide from yeast is the gas responsible for leavening bread dough.

Why B is correct:

• In alcoholic fermentation, yeast converts glucose to ethanol and CO2 via C6H12O6 → 2C2H5OH + 2CO2, where CO2 gas forms bubbles that expand the dough.

Why the others are wrong:

• A. Alcohol is a liquid byproduct of fermentation that evaporates during baking, not causing visible rising.
• C. Lactic acid is produced by bacteria in sour dough, not primary yeast action in standard bread.
• D. Oxygen is consumed by yeast in aerobic respiration, not produced.

Final answer: B