Nearly all plant cells and many bacteria are surrounded by a cell wall. However, the roles these walls play in cell division dif
fer dramatically. In plants, the wall is sufficiently rigid so that in most cells, constriction of a ring of proteins could not cause the wall to fold in and eventually pinch off. Rather, a new plant cell wall is produced between the daughter cells by the formation of a cell plate, which eventually joins with the existing cell wall. In contrast, in bacteria, the cell wall is sufficiently flexible to fold in during constriction of the FtsZ protein ring. Bacteria lack the distinct microfilaments and microtubules that dominate the cytoskeletons of plant and animal cells. However, bacteria contain proteins that are similar to actin (the building block of microfilaments) and tubulin (the building block of microtubules). The tubulin-like proteins in bacteria function in the formation of two daughter cells through binary fission.
(A) In prokaryotes, constriction of a ring of _______ (microtubules/ microfilaments/ tubulin-like proteins) cause infolding of the plasma membrane and cell wall during cell division (binary fission).
(B) In plant cells, a network of _______ (microtubules/ microfilaments/tubulin-like proteins) functions in the formation of the cell plate.
(C) In animal cells, a ring of _______ (microtubules/ microfilaments/tubulin-like proteins) constricts, creating a cleavage furrow.
Cytokinesis in the bacteria is facilitated by the presence of these conserved tubulin-like proteins. Due to the fact that their walls are flexible, constriction of these walls is possible aiding in cytokinesis. Unlike in plant that have rigid cell wall, a cell plate is involved in the formation of a new cell wall between the daughter cells. Network of microtubules determines the position of the cell plate which is mostly like a disc in the middle of the two daughter cells. Cleavage furrow occurs in animal cells which is caused by the action of the contractile ring: a ring of actin microfilament.
