How does cytokinesis differ in plant and animal cells?

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Cytokinesis is a process during which the cytoplasm of a eukaryotic cell (a cell possessing a nucleus) is divided into two daughter cells. This cell division, aside from resulting in more cells, also includes the transmission of DNA from one generation of cells to the next. All living organisms are made up of cells and come from cells which existed previously. New cells come into being via a process called mitosis and result in diploid chromosomes. Meiosis, on the other hand, results in gametes with a haploid number, which later combine with other gametes during fertilization, giving diploid chromosomes with characteristics of both parents.

Eukaryotic cells have a number of stages in their lifespan. Interphase, also known as the resting stage, includes the S stage, in which the DNA of the cells replicates itself, resulting in identical chromatids connected in the middle by a centromere. Interphase is followed by prophase, which is the first stage of mitosis. In this stage, the replicated chromosomes condense, and centrioles, described as barrel-like structures usually found in animal cells, form. These centrioles move to the opposite ends of the cells and a mitotic spindle forms from the two centrioles. The chromatids attach themselves to the spindle fibers, and during metaphase, the chromosomes line up in the middle of the cell. During anaphase, the spindle fibers shorten, pulling the chromatids apart and toward the centrioles at the opposite sides of the cell. This way, each of the daughter cells will have the same set of chromosomes. Anaphase is followed by telophase, during which the nuclear membrane forms and cytokinesis occurs. In meiosis, however, cytokinesis occurs during anaphase.

Cytokinesis in animal cells is through a process known as cleavage. In this process, a shallow groove called a cleavage furrow appears through the action of a contractile ring, which consists of non-muscle myosin and actin microfilaments. The cell is gradually pinched into two cells in what has been termed a pulling of drawstrings by the microfilaments.

Unlike animal cells, plant cells have a cell wall and no cleavage furrow. The plant cell becomes longer, and a cell plate is formed in the middle of the cell instead of a contractile ring. This is accomplished by creating an array of microtubules called a phragmoplast, which guides and helps to support the generation of the cell plate. This phragmoplast comes from the remains of the mitotic spindle, and its position is the template where the vesicles are to go. The vesicles, which are made of carbohydrates, lipids and proteins, enable the formation of the new cell wall, and the Golgi apparatus participates in their transportation to the “construction site.” A tubular vesicular network is formed, and membrane tubes continue to fuse together, transforming into membrane sheets. Cellulose and other cell wall components are deposited at this site, and finally the cell plate merges with the parental cell wall. The cell plate continues to mature until it too turns into cell wall, with its callus, plant polysaccharide being replaced by cellulose, the main component of cell walls.

An interesting difference between plant and animal cells during their dividing of the parent cell into two daughter cells is that in plant cells, the cell wall often starts in the center of the cell and grows outward to the parental cell wall, whereas in animal cells, the contractile ring causes the cell membrane to be pinched inwards from the outside. Why don’t plant cells have cytokinesis as animal cells do? The cell wall of plants is too firm to be pinched in, unlike the cell membrane of animal cells.

Resource by Will

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