Cilia and flagella of eukaryotes are composed of ___

Cilia and flagella in eukaryotic cells are indeed composed of microtubules arranged in a distinctive 9 + 2 structure. This arrangement consists of nine pairs of microtubules forming a ring around a central pair of microtubules, which is a hallmark of eukaryotic motility structures. This specific architecture is crucial for their function in cell movement and the movement of fluids across the cell surface. The coordinated bending of this structure allows cells to propel themselves or move substances in their environment effectively.

In contrast, actin filaments, intermediate filaments, and collagen fibers serve different structural and functional roles within the cell. Actin filaments are primarily involved in muscle contraction and maintaining cell shape, while intermediate filaments provide mechanical support. Collagen fibers, on the other hand, are mainly found in the extracellular matrix and are critical for tissue strength and integrity, rather than being involved in the structural composition of cilia and flagella. Thus, the 9 + 2 arrangement of microtubules is what distinguishes eukaryotic cilia and flagella and is essential for their functionality.