Definition of cytokinesis
Cytokinesis is the final process in eukaryotic cell division, which divides the cytoplasm, organelle, and cellular membrane. Cytokinesis after telophase usually occurs at the end of mitosis, but there are two independent processes. In most animals, cytokinesis begins in late anaphase or early telophase, to ensure that the chromosomes are completely separated. Movements of cytokinesis observed in the cell are caused by the same spindle network that was responsible for the separation of chromosomes. Parts of the spindle responsible for moving the chromosomes break down in late cell division, which is used in the reorganization of two new cells.
Cells can be divided evenly, known as symmetric cytokinesis, or one of the cells can maintain the majority of the cytoplasm. During male meiosis in humans, for example, at the end of meiosis, all 4 cells have the same size and the relative number of organisms. This process of spermatogenesis produces millions of small, but mostly identical sperm. Human oogenesis, on the other hand, divides through asymmetric cytokinesis. It produces a very large cell and 3 polar bodies. Small polar bodies do not form eggs. In this way, fewer eggs are produced, but they are much larger cells. Some cells, in humans and other species, do not undergo cytokinesis after mitosis and form large multi-nuclear cells.
Cytokinesis in animal cells
Whether cell division is mitosis or meiosis, cytokinesis occurs in the same manner. The cellular signal tells the cell where to divide, which forms the division plane. Around this plane, cytokinetic furrows will form, eventually closing to separate the two cells.
The final process of cytokinesis in animal cells is absconding. During absconding, the cytokinetic furoz-forming actin-myosin shrinking ring shrinks all the way, and the plasma membranes eventually undergo fission to separate the two cells.
Scientists are still not sure what causes the specification of the division plane in different cells. The process is a complex process involving many microtubules and cell signals. Once this condition is determined, the actin-myosin contractile ring should be installed. Actin and myosin are similar motor proteins that cause contraction of muscle cells. Muscle cells are packed with actin filaments, which the protein myosins can pull together when given ATP energy. This similar system is employed in dividing animal cells. Actin filaments form a ring in the division plane. Myosin proteins then begin to pull actin filaments together, forming a small ring.
Eventually, all cytoplasm and organelles are excluded from the ring. The only things left are the actin-myosin ring and microtubules narrowed by the ring. This is called the midbody structure and must also be divided to differentiate cells. It occurs during the absence process. Proteins are cut and the plasma membrane is closed. Cellularly holding the cells together dissolves and the cells can break apart. In some multicellular animals, cells are closely connected, and can also form connections between their cytoplasm and are known as gap junctions. These small bridges may form as remnants of the endoplasmic reticulum that become trapped in the midbody structure, or they may form later.
Cytokinesis in Plant Cells
Plants undergo a similar process of cytokinesis, with the difference being the stiffness of their cells. Plants are surrounded by a secondary layer, the cell wall. This extracellular structure is responsible for helping plants to form and should be established when a cell divides. To do this, plants use microtubule spindle structures, known as phragmoplast. The phragmoplast carries vesicles of cell wall material into the new cell plate. These materials, such as cellulose, interact to form a complex and strong matrix. After dividing the cell of the plate, the plasma membrane will close, and the two cells will separate.
The phragmoplast, like the centrosome of animal cells, organizes microtubules and directs their growth and decrease. The components for the new cell plate are manufactured and packaged by the endoplasmic reticulum and the Golgi apparatus. They are then sent to the phragmoplast, which forms the cell plate from the middle side. This can be seen in the graphic above. The cell plate will begin in the middle, and as soon as it is complete, the phragmoplast microtubules move outward, until they reach the present plasm membrane. This membrane will be cut off, and the cell wall will be completely fused between all the surrounding cells. Between the two cells, the trapped endoplasmic reticulum will form plasmodesmata, which are like gap junctions and allow molecules to pass from cell to cell. It is proven that plants can use these plasmodesmata as cellular communication.
Definition of Cytokinesis, Cytokinesis in Animal cell, and Plant cell