The size of a metabolizing cell is limited by its:

• A. number of mitochondria
• B. rate of cell division
• C. surface area-to-volume ratio
• D. amount of genetic material

Answer: (C)

Verified step by step guidance

1. Understand the concept of surface area-to-volume ratio: This ratio is crucial for cells because it determines the efficiency of nutrient uptake and waste removal. As a cell grows larger, its volume increases faster than its surface area, which can limit the cell's ability to exchange materials with its environment.
2. Relate the surface area-to-volume ratio to cell metabolism: Metabolizing cells require efficient transport of oxygen, nutrients, and waste products. A high surface area-to-volume ratio ensures that the cell membrane can adequately support these exchanges.
3. Compare the surface area-to-volume ratio with other factors: While the number of mitochondria, rate of cell division, and amount of genetic material are important for cell function, they do not directly limit the size of a metabolizing cell. The surface area-to-volume ratio is the primary limiting factor.
4. Consider examples of adaptations in cells: Cells like red blood cells and intestinal epithelial cells have specialized shapes (e.g., flattened or elongated) to maximize their surface area relative to their volume, enhancing their metabolic efficiency.
5. Conclude why surface area-to-volume ratio is the correct answer: The physical constraints imposed by the surface area-to-volume ratio are fundamental to cell biology and explain why cells remain small or adopt specialized shapes to maintain efficient metabolic processes.