Which protein helps pinch animal cells in two during cell division?

The protein that plays a crucial role in the process of pinching animal cells in two during cell division is microfilaments, primarily composed of actin. During cytokinesis, the final step of cell division, a contractile ring made up of actin microfilaments forms just beneath the plasma membrane at the equator of the dividing cell. This structure contracts and creates the cleavage furrow that deepens until the cell is pinched into two daughter cells.

Actin filaments are a subset of microfilaments, but they are not the complete answer to the question as they refer specifically to the protein filaments themselves rather than the entire complex involved in cell division. Tubulin is associated with microtubules, which play essential roles in cell shape and intracellular transport but do not directly contribute to the pinching mechanism of cytokinesis. Myosin is a motor protein that interacts with actin to facilitate contraction, and while it is essential for the function of the actin ring during cytokinesis, it is the microfilament structure as a whole that directly enables the pinching action.

Understanding this process highlights the importance of microfilaments in animal cell division, as they provide the structural organization necessary for the successful separation of daughter cells.