What is the pyruvic acid converted during fermentation in yeast?

In yeast, during the process of fermentation, pyruvic acid is converted into two products:

1. Ethanol: In the presence of an enzyme called pyruvate decarboxylase, pyruvic acid loses carbon dioxide (CO2) to form acetaldehyde. Acetaldehyde then undergoes reduction by the enzyme alcohol dehydrogenase, utilizing NADH as an electron donor, to produce ethanol (ethyl alcohol). This process is known as alcoholic fermentation.

The reactions involved in alcoholic fermentation are:

Pyruvic acid + H+ → Acetaldehyde + CO2

Acetaldehyde + NADH + H+ → Ethanol + NAD+

2. Lactic Acid: Under certain conditions, such as limited oxygen availability or when yeast is subjected to stress, pyruvic acid can also be converted into lactic acid through a process known as lactic acid fermentation. In this case, the enzyme lactate dehydrogenase catalyzes the transfer of a hydrogen atom from NADH to pyruvic acid, resulting in the formation of lactic acid.

The reaction involved in lactic acid fermentation is:

Pyruvic acid + NADH + H+ → Lactic acid + NAD+