A researcher compares growth of a facultative anaerobe at 37°C in identical medium containing 20 mM glucose, but with either vigorous aeration or an anoxic chamber (no O2). pH is maintained at 7.0. OD600 is measured after 4 hours.
Table (OD600 at 4 h): Aerobic: 0.95 Anoxic: 0.45
Which conclusion is most supported by the experimental results?
- Anoxic conditions increase ATP yield by enabling oxidative phosphorylation with O2
- Aerobic conditions increase ATP yield per glucose due to oxidative phosphorylation, supporting higher biomass (correct answer)
- Anoxic conditions increase growth because fermentation produces more ATP per glucose than respiration
- Aerobic conditions decrease growth because O2 directly inhibits glycolytic enzymes
Explanation: This question assesses understanding of prokaryotic growth, metabolism, and adaptation (Foundational Concept 2). Prokaryotic growth and metabolism are influenced by environmental conditions and nutrient availability, affecting cellular processes. In this experiment, oxygen availability affected growth yield in a facultative anaerobe, highlighting differences in ATP production. Choice B is correct because aerobic conditions enable oxidative phosphorylation, increasing ATP per glucose and supporting higher biomass, as shown by greater OD600. Choice C is incorrect as fermentation yields less ATP than respiration, not more, contradicting the lower anoxic growth. To tackle similar questions, focus on direct data interpretation and avoid inferring unstated conditions or unrelated pathways.