a cell membrane pinches together to divide during mitosis.
a cell membrane pinches together to divide during mitosis.
when does a cell membrane pinch together to divide?
mitosis
at the cytokinesis furrow, it is the actin-myosin contractile ring that drives the cleavage process, during which cell membrane and wall grow inward, which eventually pinches the mother cell in two. the key components of this ring are the filamentous protein actin and the motor protein myosin ii. the contractile ring assembles equatorially (in the middle of the cell) at the cell cortex (adjacent to the cell membrane). rho protein family (rhoa protein in mammalian cells) is a key regulator of contractile ring formation and contraction in animal cells. the rhoa pathway promotes assembly of the actin-myosin ring by two main effectors. first, rhoa stimulates nucleation of unbranched actin filaments by activation of diaphanous-related formins. this local generation of new actin filaments is important for the contractile ring formation. this actin filament formation process also requires a protein called profilin, which binds to actin monomers and helps load them onto the filament end. second, rhoa promotes myosin ii activation by the kinase rock, which activates myosin ii directly by phosphorylation of the myosin light chain and also inhibits myosin phosphatase by phosphorylation of the phosphatase-targeting subunit mypt. besides actin and myosin ii, the contractile ring contains the scaffolding protein anillin. anillin binds to actin, myosin, rhoa, and cyk-4, and thereby links the equatorial cortex with the signals from the central spindle. it also contributes to the linkage of the actin-myosin ring to the plasma membrane. another protein, septin, has also been speculated to serve as a structural scaffold on which the cytokinesis apparatus is organized. following its assembly, contraction of the actin-myosin ring leads to ingression of the attached plasma membrane, which partitions the cytoplasm into two domains of emerging sister cells. the force for the contractile processes is generated by movements along actin by the motor protein myosin ii. myosin ii uses the free energy released when atp is hydrolyzed to move along these actin filaments, constricting the cell membrane to form a cleavage furrow. continued hydrolysis causes this cleavage furrow to ingress (move inwards), a striking process that is clearly visible through a light microscope.
cytokinesis
the cell membrane (also known as the plasma membrane (pm) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates the interior of all cells from the outside environment (the extracellular space) which protects the cell from its environment. cell membrane is consisted of a lipid bilayer, including cholesterols (a lipid component) that sit between phospholipids to maintain their fluidity under various temperature, in combination with proteins such as integral proteins, and peripheral proteins that go across inside and outside of the membrane serving as membrane transporter, and loosely attached to the outer (peripheral) side of the cell membrane acting as several kinds of enzymes shaping the cell , respectively. the cell membrane controls the movement of substances in and out of cells and organelles. in this way, it is selectively permeable to ions and organic molecules. in addition, cell membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity and cell signalling and serve as the attachment surface for several extracellular structures, including the cell wall, the carbohydrate layer called the glycocalyx, and the intracellular network of protein fibers called the cytoskeleton. in the field of synthetic biology, cell membranes can be artificially reassembled.
cell membrane