Figure 1.
The scales of cell biology. Shown are images illustrating the range of scales in cell biology. At the smallest (∼10−9 m) is that of molecules represented by the structure of G-actin (left; reproduced from Paavilainen et al. 2008. J. Cell Biol. http://dx.doi.org/10.1083/jcb.200803100) and the largest (10−5 to 10−4 meters) is that of cell physiology, represented by a migrating fibroblast with a labeled actin cytoskeleton (right; image courtesy of Patrick Oakes). In between these length scales reside: macromolecular assemblies (10−8 to 10−7 m) of individual proteins, represented by a schematic of an Arp2/3-mediated F-actin branch (second from the left); and organelles (10−7 to 10−5 m), such as lamellipodia (third from the left), which are formed by the integration of macromolecular assemblies into a mechanochemical machine depicted as a pathway diagram. At the next level are organelle systems (10−4 to 10−5 m) that integrate organelles together for a specific aspect of cell physiology, represented by a fluorescent image of actin overlaid with vectors of actin flow at the leading edge that result from the coordination of numerous regulatory organelles across the cell (second from the right; reproduced from Thievessen et al. 2013. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201303129). Understanding the processes at this intermediate scale will greatly aid in our knowledge of how molecules construct living cells.