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. Author manuscript; available in PMC: 2017 Jun 10.
Published in final edited form as: Annu Rev Biophys. 2016 Apr 29;45:85–116. doi: 10.1146/annurev-biophys-070915-094206

Figure 8.

Figure 8

Active transport of monomers. (a) Cilia grow and shrink by adding and removing tubulin dimers at the tips of the cilia, which are also the plus end of the microtubules. A fixed number of intraflagellar transport (IFT) particles are loaded into each cilium, and these particles are carried by kinesin motor proteins (green) to the cilia tips, delivering components required for the assembly of the microtubule. They also carry the removed tubulin from the tip with the help of dynein proteins (orange). (b) Shorter microtubules get the building components faster than longer microtubules; hence, the assembly rate (blue) is length dependent. Because the disassembly rate (green) is constant, this process can lead to a steady-state microtubule length l*. The steady-state filament length distribution depends on the assembly and disassembly rate. (c) In the regime, r′ > γ, where the disassembly rate is less than the assembly rate, the distribution is peaked around a steady-state mean length. The parameters used are r′ = 500/s and γ = 1/s, and were chosen for illustration purposes.