Describe the fermentation reactions that occur after glycolysis, including which molecules are oxidized, which are reduced, and what the products are.
Input: 2NADH
- Output: 2NAD⁺, ethanol, lactate, 2ATP
- Pyruvate, the end product, serves as an electron acceptor for oxidizing NADH back to NAD⁺, which can be reused in glycolysis
-Occurs when O₂ is not present

a. Fermentation is used in the absence of oxygen to produce ATP.
b. Alcohol fermentation: pyruvate is converted to ethanol in two steps. First step releases carbon dioxide from the pyruvate, which is converted to the two-carbon compound acetaldehyde. In the second step, NADH reduces acetaldehyde to ethanol. This regenerates the supply of NAD⁺ needed for continuation of glycolysis.
c. Lactic acid fermentation: pyruvate is reduced directly by NADH to form lactate as an end product with no release of CO₂.