The physical composition of the cell as a means to promote efficiency – draft

Oftentimes in academic discussions of cellular vitality and function in living organisms, we discuss cellular behaviour as a part of a larger organ system as well as the smaller components within cells which dictate their function. This conversation has given rise to the discovery of DNA, organelles, and cell organisational systems, but though productive, tends to overshadow an equally important cellular truth: the physical composition of cells which allow cell activity to occur efficiently.  

A trend seen across all cells regardless of their variation or organism is their small size, yet typically large quantity. For instance, while a mature human blood cell averages at a diameter of 8μm, a range of 20-30 trillion blood cells are present in the body at any given time. This can be explained by the surface area to volume ratio of a cell. To sustain itself, a cell must import necessary molecules such as water and nutrients while exporting cellular waste at the same rate. When the surface area and volume of a cell are low, they maintain a 1:1 ratio allowing for homeostasis in this way. However, as the cell grows, the surface area and volume increase at different rates, imposing a dilemma. Because volume grows quicker comparatively to surface area within the ratio, large cells will be unable to exchange materials along the membrane as needed to sustain its mass, making for an inefficient cell. 

This phenomena, applied to bacterial bodies, was recorded by L.Harris et al in their study contrasting the surface area to volume ratio in rod-shaped bacteria to wild-type bacteria. The wild-type bacteria studied: A325P MreB was found to vary in its width at different parts of the cell but despite the fact, cellular mechanisms worked to maintain an optimal SA:V ratio. In mammalian organisms, slightly different mechanisms work to keep this ratio steady such as microvilli and cellular folding. For instance the microvilli (microscopic projections on the surface of the cell) present on “intestinal enterocytes increase to the apical plasma membrane area significantly” (Wu 2025) playing a critical role in nutrient uptake. In other cells such as T-lymphocytes , the increased surface area resulting from microvilli “enables cell deformations necessary for tissue intravasation and migration” (2025). 

All in all, the commonality between cells of various organisms is the unchanging SA:V ratio they must maintain as a working body. Though their internal makeup may vary across their domain and kingdom, the physical properties that allow the cell to sustain biological life stay the same. In this way, the biological and physical sects of science interact for a shared objective as the principles of physics influence the biological functions necessary for cellular survival. 

Namvar, A., Blanch, A. J., Dixon, M. W., Carmo, O. M. S., Liu, B., Tiash, S., Looker, O., Andrew, D., Chan, L.-J., Tham, W.-H., Lee, P. V. S., Rajagopal, V., & Tilley, L. (2021, January). Surface area-to-volume ratio, not cellular viscoelasticity, is the major determinant of red blood cell traversal through small channels. Cellular microbiology. https://pmc.ncbi.nlm.nih.gov/articles/PMC7757199/

Harris, L.K., Dye, N.A. and Theriot, J.A. (2014), Compensatory cell widening in an MreB mutant. Molecular Microbiology, 94: 988-1005. https://doi.org/10.1111/mmi.12811

Wu, W. (2025, April 7). Plasma membrane folding enables constant surface area-to-volume ratio in growing mammalian cells – sciencedirect. Science Direct. https://www.sciencedirect.com/science/article/abs/pii/S0960982225002659