what is the Cell Cycle? and why do cells go thrugh the Cell Cycle?

Answer 1

The cell cycle, or cell-division cycle (CDC), is the series of events in a eukaryotic cell between one cell division and the next. Thus, it is the process by which a single-cell fertilized egg develops into a mature organism and the process by which hair, skin, blood cells, and some internal organs are renewed. A specialized form of cell division is responsible for cellular differentiation during embryogenesis and morphogenesis, as well as for the maintenance of stem cells during adult life.

The cell cycle consists of four distinct phases: G1 phase, S phase, G2 phase (collectively known as interphase) and M phase. M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's chromosomes are divided between the two daughter cells, and cytokinesis, in which the cell's cytoplasm physically divides. Cells that have temporarily or reversibly stopped dividing are said to have entered a state of quiescence called G0 phase, while cells that have permanently stopped dividing due to age or accumulated DNA damage are said to be senescent. Some cell types in mature organisms, such as parenchymal cells of the liver and kidney, enter the G0 phase semi-permanently and can only be induced to begin dividing again under very specific circumstances; other types, such as epithelial cells, continue to divide throughout an organism's life.

The molecular events that control the cell cycle are ordered and directional; that is, each process occurs in a sequential fashion and it is impossible to "reverse" the cycle. There are two key classes of regulatory molecules that determine a cell's progress through the cell cycle: cyclins and cyclin-dependent kinases. Leland H. Hartwell, R. Timothy Hunt, and Paul M. Nurse won the 2001 Nobel Prize in Physiology or Medicine for their discovery of these central molecules in the regulation of the cell cycle.

Although the various stages of interphase are not usually morphologically distinguishable, each phase of the cell cycle has a distinct set of specialized biochemical processes that prepare the cell for initiatiation of the cell division. The term "post-mitotic" is sometimes used to refer to both quiescent and senescent cells. Nonproliferative cells in multicellular eukaryotes generally enter the quiescent G0 state from G1 and may remain quiescent for long periods of time, possibly indefinitely (as is often the case for neurons). This is very common for cells that are fully differentiated. Cellular senescence is a state that occurs in response to DNA damage or degradation that would make a cell's progeny nonviable; it is often a biochemical alternative to the self-destruction of such a damaged cell by apoptosis.

Answer 2

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Answer 3

Cell cycle is the process by which cells divide. There are several stages to the cell cycle: G0,G1,S,G2 and M phases. In each phase of the cell cycle the cell performs a specific function. G0 represents a newly divided cell. In G1, cells begin to synthesize proteins and nucleic acids required to replicate the DNA. The actual DNA replication takes place in S phase. All DNA is actively copied to pass on to 2 daughter cells. In G2, cells continue to synthesize proteins that will be required to undergo cell division. The cell will increase in size in preparation for division. There will also be assembly of a spindle, which segregates the DNA into a copy for each new cell. The segregation takes place during M phase, also know as mitosis. The spindle pulls the chromosomes into opposite ends of the cell and the cell wall pinches off to create 2 new daughter cells which are back to G0.

In summary: The cell cycle is the process of cell division whereby one cell and its DNA contents is replicated into 2 daughter cells which are exact copies of each other.