# Most cells are very small. What physical and metabolic constraints limit cell size? What problems would an enormous cell encounter? What adaptations might help a very large cell survive?

Assignment 2: Most cells are very small. What physical and metabolic constraints limit cell size? What problems would an enormous cell encounter? What adaptations might help a very large cell survive?

The cell is an amazing structure.  A single cell, alone, can  function as a single entity: independently acquiring the nutrients it needs to survive, adapting to its environment, and eliminating the wastes it accumulates.  Other cells, however, would rather be a part of a community of cells, like a tissue or higher organism.  These cells often become specialized; they may specialize in motility, or they may be better suited for absorption and secretion.  Whether these cells are suited for autonomous living, or become specialized for a specific function, the size of the cell is a general feature that relates to its function.  Some cells, like bacteria, can be as small as a few microns.  Other cells, like neurons, have axonal extensions that can travel a few meters long in some organisms.  For the most part, however, cells are very small.  So, what are the constraints that limit the cell to its small physical size?  What types of problems would a cell that diverges from these constraints encounter?  Finally, how do those cells that are very large, compared to the majority of cells, adapt to their larger size?  These are the questions that will be explored.

Cells are small.  The cell is the smallest unit of life; it is a functional and structural unit, enclosed by a membrane, that can metabolize and self-replicate (Tortora).   It is the metabolic requirements of the cell that, ultimately, impose the greatest constraints on the size of the cell.  Geometry teaches us that as a particular shape increases in size, the volume of that shape grows proportionately more than its surface area (Campbell).  This concept can be further elucidated with some basic geometric equations: 1.  Area = (linear measurement)2,  2. Volume = (linear measurement)3.  Thus, if the size of an ...