Q.How does cytokinesis in plant cells differ from that in animal cells?

Cytokinesis is the division of the cytoplasm, but it is carried out differently in the two kinds of cell because of the cell wall.

• Animal cells divide by a pinching-in of the cell surface. A furrow appears in the plasma membrane, usually around the middle of the cell, and steadily deepens from the outside inward until the two sides meet and the cytoplasm is separated into two daughter cells. …

Cytokinesis is the division of the cytoplasm that finishes cell division, ensuring each new nucleus ends up inside its own separate cell. The way it is achieved depends largely on whether or not the cell has a rigid wall.

In animal cells, division is brought about by a pinching-in of the cell surface. A furrow — an indentation — appears in the plasma membrane, usually around the middle of the cell. This furrow steadily deepens, cutting inward from the outside, until it reaches the centre and the two advancing sides meet. When they join, the cytoplasm is cleaved into two, producing two distinct daughter cells.

In plant cells, this pinching approach is not possible, because a plant cell is surrounded by a fairly rigid, inextensible cell wall that cannot simply be squeezed inward. Plant cells therefore construct a new dividing wall from the inside out:

• Wall formation begins in the centre of the cell, not at the surface.
• It grows outward until it reaches and fuses with the existing lateral (side) walls. …

Step 1 — Identify the one structural difference that forces a different mechanism: plant cells have a rigid cell wall, animal cells do not.

Step 2 — Describe the animal-cell method, possible only without a rigid wall: a furrow appears in the plasma membrane and deepens inward until the cell pinches into two. …