What is the primary component of microfilaments involved in muscle contraction?

The primary component of microfilaments involved in muscle contraction is actin. Actin is a globular protein that polymerizes to form long, thin filaments known as F-actin, which are crucial for various cellular processes, including muscle contraction.

In muscle cells, actin filaments form a complex with myosin, another protein that is critical for contraction. During the contraction process, the myosin heads bind to the actin filaments, forming cross-bridges that pull the filaments past one another. This sliding filament mechanism leads to the shortening of the muscle cell, ultimately resulting in muscle contraction.

Other components like myosin, while essential for muscle contraction, are not classified as microfilaments. Myosin is a motor protein that interacts with actin. Tubulin, on the other hand, is the main component of microtubules, which serve different functions such as maintaining cell shape and facilitating intracellular transport. Keratin is a structural protein found in epithelial cells and does not play a role in muscle contraction. Thus, actin is the definitive primary component of microfilaments involved in muscle contraction.