Which process regenerates NAD+ and produces ethanol, lactic acid, or CO2?

The process that regenerates NAD+ and produces ethanol, lactic acid, or CO2 is fermentation. During fermentation, cells convert carbohydrates into acids or alcohol in the absence of oxygen, enabling glycolysis to continue by recycling NADH back to NAD+. This regeneration of NAD+ is crucial as it allows glycolysis to persist and produce ATP, even when oxygen is limited.

In alcohol fermentation, commonly occurring in yeast, glucose is converted into ethanol and carbon dioxide. In lactic acid fermentation, which takes place in certain bacteria and animal muscle cells, glucose is converted into lactic acid. Both types of fermentation serve to maintain the flow of energy production by ensuring a steady supply of NAD+, which is essential for the continuation of glycolytic processes. This is vital in conditions where aerobic respiration cannot occur, such as during intense exercise or in an anaerobic environment.