Final answer:
Actin filaments play a crucial role in maintaining the cell's structural integrity, supporting cellular motion, and contributing to various cell junctions, but they do not exclude organelles; that function is attributed to intermediate filaments.
Step-by-step explanation:
The role of actin filaments in the cell is diverse, encompassing a variety of structural and motility functions. They reinforce the plasma membrane, support cellular motion and shape changes through mechanisms like stress fibers, and are involved in muscle contraction, cell support, and cytoplasmic movements.
Actin filaments also play a role in cell-to-cell and cell-to-matrix junctions, which are crucial for maintaining the structural integrity of tissues. However, actin filaments do NOT exclude organelles; instead, this is a role typically associated with intermediate filaments, which help to anchor organelles in place within the cell.