Final answer:
Older microfilaments would contain more ADP because the hydrolysis of ATP to ADP at the - end of the actin filament weakens the binding between monomers, leading to an increase in the likelihood of filament disassembly.
Step-by-step explanation:
Microfilaments, primarily composed of the protein actin, are crucial for various cellular motions. Within these structures, actin monomers polymerize to form a helical structure, which is inherently unstable due to the hydrolysis of ATP to ADP at the - end of the filament. The aging process of microfilaments means that older filaments would have actin subunits with more bound ADP, as newer subunits with ATP are added to the + end, pushing older ADP-bound subunits toward the - end. Consequently, older microfilaments would contain more ADP, leading to a weaker association between monomers, making the filament more likely to disassemble at the - end, a process balanced by the addition of new ATP-bound actin monomers at the + end.
In summary, older microfilaments would contain more ADP, as the structural dynamics of microfilaments show that the ADP-bound actin subunits are predominantly found at the - end, where they promote filament disassembly through reduced monomer binding strength.