When you drill a hole in your concrete house wall, your household DIY drill generates about 1000 Newton. The bit in your drill rotates at 2000-3000 RPM by a powerful electric motor with a gearbox that can increase or decrease its speed. To overcome the hardness of the wall material, we use a diamond bit and provide ‘extra’ energy by pushing the drill against the wall. If we drill a 2-cm-deep screw hole, we generate “work” on the wall by applying the force on these 2 cm. No matter how powerful your drill is, the amount of “work” for the hole is essentially the same.

At the molecular level, the story is quite different. Imagine, for example, our Molecular NanoMachine. Its size is only 1 nm, and its rotors can spin at 120,000,000 RPM. The energy of the motor is obtained from light, and thus, light energy is converted into mechanical force. If we assume that the footprint of the molecular machine on the surface of the lipid bilayer membrane is about 1 nm, we can then use simple formulas to determine the force exerted by drilling a pore into the bilayer lipid membrane. This is about 500 picoNewton.

This is about one order of magnitude larger than the mechanical force generated by other biological molecular machines that exist in our body (e.g., myosin, actin, ribosome).

Can the cell resist that force? In brief, the answer is no! There are several studies on membrane rupture and pore formation, and they are beyond the context of the blog. Nonetheless, based on the calculation above, the stress being applied on the lipid bilayer membrane by the Molecular NanoMachine is about 10 times GREATER than rupture stress for most lipid bilayer membranes.