Final answer:
Actin-based microfilaments are composed of two intertwined strands of actin monomers forming a helical structure essential for muscle contraction and cellular movements. They work with myosin to enable cell motility and are a key component of the cytoskeleton.
Step-by-step explanation:
Structure of Actin-based Microfilaments
The structure of actin-based microfilaments is intricate yet vital for cellular functions. These microfilaments consist of two intertwined strands of actin, a type of globular protein. Actin monomers polymerize to form linear filaments known as F-actin, which then twist together to form a helical structure with a diameter of about 7 nm. This dual-stranded helix forms the core of actin filaments, which function dynamically within the cell, constantly assembling and disassembling.
Actin-based microfilaments, along with motor proteins such as myosin, play a critical role in muscle contraction and cellular movements, including ameboid movement, cytoplasmic streaming, and during cell division as part of the contractile ring. Actin filaments interact with myosin in the presence of ATP, which provides the energy for movement and contraction. These interactions are particularly well-understood within the context of skeletal muscle contraction, where actin and myosin filaments slide past each other to shorten and thus contract the muscle.