Free ATP-actin monomers are held at concentration

PHYSICS · Multi-part · Fermi University Physics · Biophysics & Medical Physics · Macromolecules, membranes and cell architecture · Macromolecules, membranes and cell architecture

Forces, Machines and Signals, Ch Filaments, networks and the mechanics of whole cells

Problem

c = 0.50\,\mathrm{\mu M}

. At the barbed end, the on- and off-rate constants are

k_{\rm on} = 11.6\,\mathrm{\mu M^{-1}\,s^{-1}}

and

k_{\rm off} = 1.4\,\mathrm{s^{-1}}

, and each subunit added lengthens the filament by

\delta = 2.7\,\mathrm{nm}

. ((a)) Find the barbed-end critical concentration

c_c = k_{\rm off}/k_{\rm on}

. ((b)) Find the net elongation rate

v = \delta(k_{\rm on}c - k_{\rm off})

c = 0.50\,\mathrm{\mu M}

, and state whether the end is growing or shrinking.

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