The Reproduction of Cells
As I wrote in my previous essay, cells are organisms perfectly made and organized in such an extraordinary manner. Everything that happens within our cells, up to what we know, could fit a description of many books.
Every day we grow and what our eyes can only let us see takes us to the conclusion that we are growing because all of a sudden our appetite grew stronger and our clothing is getting smaller. We have been filling our body with nutrients throughout our childhood years, then, when in the teenage years, we notice that our body is rapidly developing and extending its size and strength. However, have you ever wondered what happens deep within your body; what gives it the capability of growing about six inches in a few weeks?
You see, in the cellular level, there is a whole world going on inside of you that is enabling your bones, tissue, organs, and muscles to grow. Adults say, “Oh intolerable teenagers, with their emotional and hormonal attitudes. Get those annoying kids with the ‘attitude’ out of here.” And many times this is true in teens and we blame hormonal changes. I don’t make hormones responsible for the teens’ attitudes, but one thing is reality, and that is that in these years we have started to grow and that means our cells have started to communicate with one another saying, “we think it is time here in the toe, my dear foot, we need to reproduce and grow in number.”
Hormonal signaling, also known as Endocrine signaling, is occurring inside our bodies during this process of cell reproduction. In order to control the growth, cells have to communicate with each other. Cells in some areas of our body are sending a chemical signal (hormone) to other sells in different areas of our body and are telling each other to perform a specific task, in this case, to reproduce, which is an important phase in the life of cells and their cycle.
A signal called ligand is sent through the hormone to a specific cell. The receiving cell, in turn, catches the signal through its, what I call “ear”, that is really just a substance known as the G Protein. This part of the cell communication process is the reception.
After receiving the signal, the G Protein releases a substance named Guanosine Diphosphate (GDP) and picks up another substance called Guanosine Triphosphate (GTP). The GTP will trigger an energetic reaction that will cause the G Protein to move, bind with an enzyme and activate it. This is the transduction phase of the communication that releases a response in which the cell will perform the activity it has been required, here it will be reproduction.
The cell starts to enter a process of duplication, where she creates two genetically identical daughter cells, as if they were clones of the original cell. This process is known as Mitosis. In this phase of reproduction a replica of the DNA (our genetic structure) that resides in chromosomes, which are inside of the nucleus of the cell, is made. The DNA polymerizes and splits in half.
Each one of our cells has 46 chromosomes that are grouped inside of chromatins and these chromosomes, that the cell may reproduce, form clones of themselves known as chromatids. Chromatids start to pack themselves inside of coils within a cell and start to increase in density. In this, all protein structures form and start to move into place that the cell may be able to copy itself. The membrane that surrounds the nucleus or Nuclear Envelope begins to weaken and dissolve to allow the separation of the cloned chromosome or chromatid from the original copy of the DNA. This is the prophase, the first in mitosis.
Next, the metaphase forms and brings forth a structure called the spindle. The sister chromatids align as if they were face to face attached to each other by a centromere, in the center of the nucleus. The structure formed by the sister chromatids, is known as the Kinetochore. Lined up ate each “polar” end of the cell are centrosomes that sort of “enlighten the path” of the chromosome to split from its sister and go to one “polar” end of the cell through microtubules made of a polymerized substance called Tubulin. These microtubules are kind of like the “path” the chromosome is carried through. As the chromosome is carried on the shoulders of a motor protein that is engine by ATP and ADP, the polymerized Tubulin that conforms the microtubules, depolymerizes or breaks down, making them shorter at each step of the protein.
Finally in the anaphase the chromatids separate from each other by moving to each “polar” end of the cell. This phase gives form to the telophase in which we have obtained the result of two new nuclei that will cause the cell to conclude this process and be able to divide or reproduce.
Now each cell will be able to move about in its specific function in cytokinesis, which means that mitosis has been complete. It is important to mention, though, that the whole cell cycle is controlled by proteins called Kinases. These proteins control all the communication signals that are recorded inside a cell. Therefore, in reproduction, for example, they would be the ones in charge to tell the cell when to start or stop reproducing. You don’t want the cell to overproduce or there may be malfunctions within your body and it would be that there are sicknesses in the cell and deformations may take place.
This is all the reproductive cell cycle. Thanks to this system, we are able to grow perfectly. Of course, the correct ingest of nutrients is very necessary for the right development of our body cells and their proper reproduction. A very similar process takes place to regenerate our skin when we scrape our knees or cut ourselves.