Question

Which one of the following molecules is produced initially when glucose breaks down in the cytoplasm of a cell in aerobic as well as anaerobic respiration ?

• A. Lactic acid
• B. Ethanol
• C. Carbon dioxide
• D. Pyruvate

Hint:

Remember: Glycolysis produces pyruvate in the cytoplasm before any other products are formed.

Answer 1

The Correct Option is D

When glucose breaks down in the cytoplasm of a cell, the first step is glycolysis, which occurs in both aerobic and anaerobic respiration. In glycolysis, one molecule of glucose (6-carbon) is broken down into two molecules of pyruvate (3-carbon) along with the release of a small amount of energy (ATP). Further breakdown of pyruvate depends on the presence or absence of oxygen: - In aerobic respiration, pyruvate enters mitochondria and is converted into carbon dioxide and water. - In anaerobic respiration, pyruvate is converted into lactic acid (in animals) or ethanol and carbon dioxide (in yeast). Therefore, the first molecule formed is always pyruvate.