Final answer:
Cilia and flagella possess a “9 + 2 array” of microtubules, with motile cilia facilitating movement and primary sensory cilia involved in sensing. The cytoskeleton consists of microfilaments, intermediate filaments, and microtubules, each playing distinct roles in the cell. Plant, animal, and bacterial cells have different types of boundaries like cell walls and plasma membranes.
Step-by-step explanation:
Arrangement of Microtubules in Cilia
Both cilia and flagella share a core structural arrangement of microtubules known as the “9 + 2 array”. This configuration consists of nine peripheral microtubule doublets encircling a central pair of single microtubules. The motion of a motile cilium is facilitated by the sliding of these microtubules against each other, driven by motor proteins like dynein and kinesin.
Key Differences Between Motile Cilium and Primary Sensory Cilium
Motile cilia are responsible for moving fluids across cell surfaces or propelling cells, as seen in sperm cells. In contrast, a primary sensory cilium does not have the same 9 + 2 structure—often it has a “9 + 0” arrangement—and serves as a sensor for molecular signals rather than aiding in movement.
Cytoskeleton and Cell Components
The cytoskeleton is comprised of microfilaments, intermediate filaments, and microtubules. Microfilaments are actin-based and play a crucial role in cell motility and shape, intermediate filaments provide structural support and resilience, and microtubules help maintain cell shape, enable intracellular movement, and are essential in cell division, among other roles. Cilia and flagella are formed from microtubules and facilitate locomotion and sensation, but differ from similar structures in prokaryotic cells.
Cell Boundaries
Plant, animal, and bacteria cells clearly differentiate in their boundaries. While plant cells are encased within a rigid cell wall, animal cells are bounded by a more flexible plasma membrane, and bacterial cells, depending on their classification, can have a cell wall that is structurally different from that of plants.