Which process occurs when cells release energy in the absence of oxygen and often produces byproducts like lactic acid or alcohol?

Which process occurs when cells release energy in the absence of oxygen and often produces byproducts like lactic acid or alcohol?

• A. Fermentation
• B. Glycolysis
• C. Krebs cycle
• D. Electron transport chain

Answer: (A)

Fermentation is the process cells use to release energy without oxygen. It follows glycolysis and regenerates NAD+ so glycolysis can keep producing ATP when oxygen isn’t available. Depending on the organism, the end products are lactic acid (in animals) or ethanol and carbon dioxide (in yeast). This pathway gives far less ATP than aerobic respiration, because it stops after regenerating NAD+. The Krebs cycle and electron transport chain require oxygen and don’t produce lactic acid or alcohol as their typical byproducts, so they don’t operate in this anaerobic context.

Fermentation is the process cells use to release energy without oxygen. It follows glycolysis and regenerates NAD+ so glycolysis can keep producing ATP when oxygen isn’t available. Depending on the organism, the end products are lactic acid (in animals) or ethanol and carbon dioxide (in yeast). This pathway gives far less ATP than aerobic respiration, because it stops after regenerating NAD+. The Krebs cycle and electron transport chain require oxygen and don’t produce lactic acid or alcohol as their typical byproducts, so they don’t operate in this anaerobic context.