Beyond pH control, carbon dioxide (CO₂) contributes to mammalian cell culture metabolism in several ways. Which statements describe its roles?
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ACO₂ participates in de novo synthesis of purines and pyrimidines via one-carbon chemistry
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BCO₂ supports cellular respiration equilibria and gas exchange
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CCO₂, with bicarbonate, allows monitoring and stabilization of culture pH
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DAll of the above
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ENone of the above
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:CO₂ is not merely an incubator setting; it is a metabolically relevant molecule in cultured cells. Through the bicarbonate buffer system and carboxylation reactions, CO₂ affects biosynthesis and homeostasis.
Given Data / Assumptions:
- Bicarbonate-buffered media are used.
- Cells require balanced carbon sources and proper pH.
- Standard incubators regulate CO₂ around 5%.
Concept / Approach:CO₂ dissolves to form carbonic acid, establishing the bicarbonate buffer that sets pH. It also serves as a carbon donor in carboxylation and contributes to biosynthetic pathways, including nucleotide synthesis. Proper CO₂ tension maintains physiological conditions for respiration and enzyme activities.
Step-by-Step Solution:
Recognize CO₂ as part of the buffer system (pH control and monitoring).Note its biochemical role in one-carbon metabolism and nucleotide biosynthesis.Acknowledge its role in gas exchange and respiration equilibria.Verification / Alternative check:Media datasheets and biochemistry texts describe both buffering and metabolic roles for CO₂/HCO₃⁻ systems, confirming the comprehensive answer.
Why Other Options Are Wrong:
Any single role alone is incomplete; “none” contradicts standard cell biology.Common Pitfalls:Viewing CO₂ as a pH knob only; neglecting its integration into cellular carbon flux.
Final Answer:All of the above.