By Andy Kahn
Cancer is generally defined as a growth or tumor that results from abnormal and uncontrolled cell division. Normal cells of the body, with a few exceptions, constantly undergo division as old and injured cells die off and are replaced. The process of Controlled growth and death of normal cells is referred to as homeostasis, and its goal is to maintain a healthy balance in the life. To achieve this goal, cellular growth and division occurs in a process called the cellular cycle, and its steps are carefully controlled by a variety of genetic and molecular feedback mechanisms. In cancer cells, any one or several of these mechanisms malfunction, allowing their growth to proceed unchecked.
The cellular cycle is an orderly, four-stage process. The cell starts the cycle when it is engaged in its normal functions. It eventually prepares to make a copy of itself by entering a phase in which it's DNA the genetic material-replicates, resulting in duplicate genetic material. It then returns to its normal functions for a while before entering the final phase, when the cytoplasm and duplicate genetic material separates producing two identical cells. Normal cells follow the steps of the cellular cycle in an orderly fashion.
Cancer cells also follow these steps, but they bypass the controls that keep too many of them from entering the cycle at once and that make them die off when they should. Cancer cells do not stop dividing the way the normal ones do. They differ from normal ones in a number of ways. Normal cells require external growth factors to enter the cellular cycle. External growth factors are substances from the surrounding environment that trigger division. Cancer cells live independently of these growth factors, so they continually divide. Normal ones limit their division when they come into contact with other cells.
Cancer is generally defined as a growth or tumor that results from abnormal and uncontrolled cell division. Normal cells of the body, with a few exceptions, constantly undergo division as old and injured cells die off and are replaced. The process of Controlled growth and death of normal cells is referred to as homeostasis, and its goal is to maintain a healthy balance in the life. To achieve this goal, cellular growth and division occurs in a process called the cellular cycle, and its steps are carefully controlled by a variety of genetic and molecular feedback mechanisms. In cancer cells, any one or several of these mechanisms malfunction, allowing their growth to proceed unchecked.
The cellular cycle is an orderly, four-stage process. The cell starts the cycle when it is engaged in its normal functions. It eventually prepares to make a copy of itself by entering a phase in which it's DNA the genetic material-replicates, resulting in duplicate genetic material. It then returns to its normal functions for a while before entering the final phase, when the cytoplasm and duplicate genetic material separates producing two identical cells. Normal cells follow the steps of the cellular cycle in an orderly fashion.
Cancer cells also follow these steps, but they bypass the controls that keep too many of them from entering the cycle at once and that make them die off when they should. Cancer cells do not stop dividing the way the normal ones do. They differ from normal ones in a number of ways. Normal cells require external growth factors to enter the cellular cycle. External growth factors are substances from the surrounding environment that trigger division. Cancer cells live independently of these growth factors, so they continually divide. Normal ones limit their division when they come into contact with other cells.
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