Force sensing is fundamental and made overt in hearing, touch, gravitropism and thigmomorphogenesis. Their molecular workings, however, are unclear. While current research is dominated by biochemistry and genomics, one should remember that the 17th century clockwork physics remains strictly enforced.
The amphipathic nature of phospholipids produces a highly anisotropic environment with localized tensions exerted on embedded proteins. Changes in these mechanical forces can activate proteins that underlie myriad biological phenomena. These forces were first illustrated with such biophysical models as the bacterial mechanosensitive ion channels. That the Drosophila phototransduction channels are ultimately operated by bilayer mechanical force recently caught many by surprise. Meanwhile, the voltage-gated K+ channel, central to neurobiology, is also found to be ultra-sensitive to bilayer stretch. Although ion channels are used as examples because they can be gauged accurately, lipid-force sensitivity has been shown for >18 structurally disparate membrane protein superfamily.
Of all the forces cells sense, osmotic pressure on the bilayer appears to be to have come first. Because it is the measure of water, this vital sense remains universal, manifests in prokaryotes, protists, animals, and plants alike.