Which of the following factors is believed to limit the size of most bacterial cells?

• A. The presence of a cell wall composed of peptidoglycan
• B. The amount of DNA in the nucleoid region
• C. The number of ribosomes present in the cytoplasm
• D. The rate of nutrient diffusion across the cell membrane

Answer: (D)

Verified step by step guidance

1. Understand that bacterial cell size is influenced by multiple factors, but the key limiting factor is related to how efficiently the cell can exchange materials with its environment.
2. Recall that nutrient uptake and waste removal occur primarily through diffusion across the cell membrane, which is a passive process dependent on surface area.
3. Recognize that as a bacterial cell grows larger, its volume increases faster than its surface area, leading to a decreased surface area-to-volume ratio.
4. Understand that a lower surface area-to-volume ratio limits the rate at which nutrients can diffuse into the cell and waste products can diffuse out, thus restricting further growth.
5. Conclude that the rate of nutrient diffusion across the cell membrane is the primary factor limiting bacterial cell size, rather than structural components like the cell wall, DNA amount, or ribosome number.