The cilium is a sort of “arm” of a cell that either moves stuff or feels stuff:
In Current Biology, Gaia Pigino wrote a “Primer” on Intraflagellar Transport (IFT). It’s called intraflagellar because a cilium is a type of flagellum (Latin for whip), which in the generic sense means a whiplike structure that can move. Both cilia and flagella use the IFT system for construction because both need to transport their building blocks down a shaft from the base to the distal tip. From the railcar’s perspective, the tip would seem a long way away.
There are motile cilia, like the ones that keep our windpipes clean and propel sperm cells, and “primary” cilia, which act as sensory antennae on almost all cells. Accurate construction of cilia is vital. When things go wrong, a host of problems called ciliopathies can result in severe diseases and death. Evolution News has mentioned these briefly in previous years (here, here, and here).
Consider first how many players are needed to build a cilium. Pigino’s parts list begins with microtubules in a 9+2 arrangement going up the cilium from base to tip. The two center microtubules are singlets; the outer ring of 9 are in doublet pairs. Riding on those rails are two engines: kinesin-2, which travels from base to tip (anterograde), and dynein-2, which goes from tip back to the base. Kinesin-2 has a head, stalk, hinge and two “feet” (called heads) that walk on the microtubule while carrying a load; the engine contains six protein subunits. Dynein-2 also has a motor, stalk, linker and tail, and is powered by two AAA+ domains that spend ATP for power. Those are the two engine types, and they work in teams along the microtubules.Evolution News, “Cilium and Intraflagellar Transport: More Irreducibly Complex than Ever” at Evolution News (June 30, 2021)
Of course, Darwinism is dead. It is the Darwin profs and the institutional structure that supports them who are very much alive.