In the context of cellular respiration, where do the bubbles in beer or champagne primarily come from?

• A. Nitrogen gas added during bottling
• B. Oxygen released during photosynthesis
• C. Carbon dioxide produced during alcoholic fermentation
• D. Water vapor formed during condensation

Answer: (C)

Verified step by step guidance

1. Understand the context of the question: The problem is asking about the source of bubbles in beer or champagne, which are produced during the process of alcoholic fermentation, a part of cellular respiration in yeast.
2. Recall the process of alcoholic fermentation: Yeast cells break down glucose (C₆H₁₂O₆) in the absence of oxygen to produce ethanol (C₂H₅OH) and carbon dioxide (CO₂). This is an anaerobic process.
3. Write the chemical equation for alcoholic fermentation: $C{6}_{12}{6}_6\to 2C{2}_5\mathrm{OH}+2\mathrm{CO}{2}_{}$. The carbon dioxide produced is responsible for the bubbles.
4. Explain why other options are incorrect: Nitrogen gas is not added during bottling, oxygen is not released during photosynthesis in this context, and water vapor is not the source of bubbles in beer or champagne.
5. Conclude that the bubbles in beer or champagne primarily come from carbon dioxide (CO₂) produced during alcoholic fermentation by yeast.