Final answer:
The Arp 2/3 complex accelerates actin polymerization through nucleation and branching, providing additional sites for monomers to join the filament.
Step-by-step explanation:
The Arp 2/3 complex accelerates actin polymerization through nucleation and branching. The complex consists of seven subunits, including Arp2 and Arp3, which form a stable complex. When activated, the Arp 2/3 complex binds to the side of an existing actin filament and nucleates the formation of a new actin filament at a 70-degree angle. This branching process increases the rate of actin polymerization by providing additional sites for monomers to join the filament.