Molecular motors are naturally occurring machines that walk, literally walk, around inside cells, moving things to where they need to go. There are many, many of them working away inside you right now!
One part of my PhD focused on the molecular motor called myosin-V. It is as much a 'motor' as the internal combustion engine, but the different physics at its scale of motion (myosin-V steps by no more than 36 nm at a time, 36 millionths of a millimetre) requires a different mechanism to acheive transport.
A myosin-V molecule (me) consists of two 'neck domains' (my legs) which bind to the track (the floor), and is connected to the cargo it is transporting (the ball) by a tether (my torso and arm). The motor is continually being buffeted around by surrounding water molecules (the four supporting dancers). Its world, comprised by the interactions with these molecules, is inherently random (represented by the background sounds). This randomness leads to apparently useless flailing around of the motor legs, with backward steps as well as forward ones. The motor, however, is capable of transforming this randomness into a forward motion along its track, on average, and eventually reaches its destination.
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