part of part of axonemal microtubule axonemal central pair C1 axonemal microtubule One of two microtubules present in the axonemal central pair. It is distinguishable from the C2 axonemal microtubule (also called C2 tubule) by the presence of differing protein components of the projections. GO:1990719 cellular_component 2015-03-27T22:55:12Z krc C1 tubule