How do cells determine what size to grow before dividing?
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To determine how large a cell should be it, it must at least alter growth rates and the cell cycles. Different tissues have various abilities to maintain these appropriate sizes—some more effective than others. In many tissues, if cells are the wrong size they don’t perform well.
It is the number of cells, not the size of an individual’s cells that makes one person larger than others. Despite this, organs maintain exact standards of cell size even when people are rapidly growing. During the production of new cells from stem cells, they can become much larger, by orders of magnitude compared with the original stem cell. Bone cells increased their size by more than 10 times when the bone is growing. In the pancreas there are two different cells, right next to each other, where one is two times the size of the other. These examples show that size is highly regulated.
B0006279 Ciliated epitheliumReceptors on the cell’s membrane respond to many signals from the environment that adjust the size of cells—cytokines, growth factors and molecules that signal cell division. Some factors increase cell growth and other stimulate the cell division cycle producing more cells. Some of the same factors function differently for specific cells. Research shows that, although these signals determine the average size of cells, they don’t actually determine the variance of individual cells. This needs the ability of the individual cell to participate in the process. Is there an optimal size for cells to function?
When cells are first produced from division, there is a time that they are growing when ultimate size can be determined. One way is to only have cells that have achieved the “correct” size to be able to divide and make more cells. Large cells divide rapidly to cut down the size of the cell in half. Research shows size measurement in the G phase of cell division.
The very complex cell cycle is the process where cells divide and make a new one. It is described as the interphase and then mitosis. The interphase is broken up into parts. The G phase is the “gap” between getting ready and then actually dividing. In G1 cells increase in size and are prepared for the very complex process of copying of the DNA.
The next phase is called S for “synthesis” of DNA. This is when the complex process where copies of the chromosomes are made and divided.