Final answer:
Cytoskeletal filament growth occurs spontaneously when the concentration of free subunits exceeds the critical concentration, with dynamic growth and shrinkage at the plus and minus ends respectively, particularly influenced by ATP and ADP binding.
Step-by-step explanation:
The growth of a cytoskeletal filament proceeds spontaneously if the concentration of free subunits (C) is higher than the critical concentration (cc). In cytoskeletal polymers such as actin, the filaments exhibit different dynamics at their two ends, known as the plus and minus ends. The plus end generally has a higher rate of monomer association and disassociation compared to the minus end, leading to a dynamic process termed 'treadmilling' where one end grows while the other shrinks within certain monomer concentration ranges.
Specifically, the non-equilibrium dynamics of actin filament growth involve the polymerization and depolymerization of actin subunits, with the presence of ATP and ADP influencing monomer binding strength and stability. Experiments have shown the effects of substrate stiffness on cytoskeletal organization, demonstrating that the cytoskeleton's response is not only influenced by the concentration of free subunits but also by mechanical cues.