Final answer:
Yeast uses the enzyme pyruvate decarboxylase to catalyze the fermentation process, converting pyruvic acid into acetaldehyde and releasing CO2. Alcohol dehydrogenase then reduces the acetaldehyde to ethanol, which is useful in the production of alcoholic beverages and in baking bread.
Step-by-step explanation:
Yeast contains an enzyme known as pyruvate decarboxylase and this catalyzes the fermentation process. The fermentation process begins with pyruvate decarboxylase catalyzing the removal of a carboxyl group from pyruvic acid, releasing carbon dioxide as a byproduct and producing acetaldehyde. This enzyme requires a coenzyme derived from vitamin B1, also called thiamine or thiamine pyrophosphate (TPP).
The second enzyme involved is alcohol dehydrogenase, which oxidizes NADH to NAD+ and concurrently reduces acetaldehyde to ethanol, the form of alcohol found in beer and other alcoholic beverages. This is vital for the production of alcoholic beverages as well as causing bread to rise by generating CO2 bubbles.