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The cell cycle is a series of complex, ordered, sequential events that control how a single cell divides into two cells, and involves several different phases. The phases include the G1 and G2 phases, DNA replication or S phase, and the actual process of cell division, mitosis or M phase. [ 1 ]
The entry and exit of large molecules from the cell nucleus is tightly controlled by the nuclear pore complexes (NPCs). Although small molecules can enter the nucleus without regulation, [ 1 ] macromolecules such as RNA and proteins require association with transport factors known as nuclear transport receptors , like karyopherins called ...
In yeast, just one CDK (Cdc28 in S. cerevisiae and Cdc2 in S. pombe) controls the cell cycle. [59] However, in animals, whole families of CDKs have evolved. [60] [61] Cdk1 controls entry to mitosis and Cdk2, Cdk4, and Cdk6 regulate entry into S phase. Despite the evolution of the CDK family in animals, these proteins have related or redundant ...
Viral entry is the earliest stage of infection in the viral life cycle, as the virus comes into contact with the host cell and introduces viral material into the cell. The major steps involved in viral entry are shown below. [ 1 ]
Several types of cells support an action potential, such as plant cells, muscle cells, and the specialized cells of the heart (in which occurs the cardiac action potential). However, the main excitable cell is the neuron , which also has the simplest mechanism for the action potential.
DNA damage is the main indication for a cell to "restrict" and not enter the cell cycle. The decision to commit to a new round of cell division occurs when the cell activates cyclin-CDK-dependent transcription which promotes entry into S phase. This check point ensures the further process. [10]
Lysosomes carry out intracellular digestion, in a process called phagocytosis (from the Greek phagein, to eat and kytos, vessel, referring here to the cell), by fusing with a vacuole and releasing their enzymes into the vacuole. Through this process, sugars, amino acids, and other monomers pass into the cytosol and become nutrients for the cell.
The cell cycle is a cycle rather than a linear process because the two daughter cells produced repeat the cycle. This process contains two main phases, interphase, in which the cell grows and synthesizes a copy of its DNA, and the mitotic (M) phase, during which the cell separates its DNA and divides into two new daughter cells. [7]