What term describes the biological process that breaks down carbohydrates to lactic acid as the main end product?

• A. Lactic acid fermentation
• B. Alcoholic fermentation
• C. Photosynthesis
• D. Ecosystem

Answer: (A)

This question focuses on how carbohydrates are metabolized in the absence of oxygen to form lactate. When oxygen is limited, cells still want to generate ATP, so glycolysis proceeds and pyruvate builds up. Lactic acid fermentation uses lactate dehydrogenase to convert pyruvate into lactate while oxidizing NADH back to NAD+. This regeneration of NAD+ lets glycolysis keep running and producing ATP without oxygen, with lactate as the main end product. That’s why the term lactic acid fermentation is the best fit.

Alcoholic fermentation also starts from pyruvate, but it converts it to acetaldehyde and CO2, then to ethanol. Photosynthesis builds sugars using light energy, not break them down to lactate. Ecosystem is a system, not a metabolic process.