Final answer:
Integrins are heterodimeric receptors with two subunits that connect cells to the ECM, especially to collagen fibers, and participate in the formation of focal adhesions, which are crucial for cell-ECM adhesion and signaling.
Step-by-step explanation:
Integrins are heterodimeric transmembrane receptors that play a crucial role in connecting cells to the extracellular matrix (ECM), such as collagen fibers, and in the formation of focal adhesions. These molecules have two units or subunits that bind to ECM components and interact with a range of intracellular proteins like talin and vinculin, forming a complex that links the ECM to the cell's cytoskeleton. The ECM, containing structural proteins like collagen, fibronectin, and laminin, acts as a support structure for cells, while focal adhesions serve dual functions as mechanical anchor points and signaling hubs that regulate processes including cell migration, differentiation, and response to environmental stiffness.