(Sujin Ko, sujinko93@gmail.com)
Wednesday, March 30, 2011
The Cells That Make Us
In Chapter 7, Shubin describes all of the different kinds of cells that together make up the different organs and parts of the body. All of these cells that constitute all of these different organs has a distinct role in bodily functions. "What happens when you take away some bacteria from a mat of bacteria? You end up with a smaller mat of bacteria. What happens when you remove some cells of a human... say from the heart or brain? You could end up with a dead human" (117). Why are some of these cells more important than others when it comes to bodily functions? Which type of cells are more important for our body to continuously function properly? Why is it so important for cells such as skin cells to be sloughed off and continuously renewed, and why does our skin become wrinkly when we grow old if our skin cells are constantly able to produce new cells and replace our old ones?
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ReplyDeleteFirst, to clarify the mat of bacteria example, Shubin discusses bacteria and human cells staring on page 117 in the “Habeas Corpus: Show Me the Body” section. The main reason he brings up bacteria is to distinguish between an organism with a body (humans) and an organism without a body (bacteria). In a mat of bacteria, there is a plethora of bacterium, but it is key to recognize that each cell of bacteria is its own individual--it can survive on its own and carry out all of its necessary metabolic processes. A key feature of bacteria is that they sexually reproduce relatively rapidly via binary fission (the prokaryotic cell reproduction process). In binary fission, the single circular DNA is replicated and the cell splits into two roughly equal parts in which each cell receives a copy of the cell’s DNA. So, although there are many cells present in the mat of bacteria, each bacterium cell is its own individual and by removing some bacteria, you do not kill any of the other bacteria remaining. In fact, assuming there is food for the bacteria, the bacteria left would continue to reproduce.
ReplyDeleteHowever, for humans, there are different kinds of cells with different functions. All of these cells need to be present for the human to survive. Now, I would not say any individual type of cell is more important to the survival of a human, but it is apparent that if you removed a few skin cells you would not die, though if you removed some brain cells you could die or be seriously injured. One important reason for this is different types of human cells divide at different rates. Some cells such as hair, skin, and fingernail cells divide at a rapid rate, whereas brain and nerve cells “are rarely produced after [humans] are a few months old” (http://anthro.palomar.edu/biobasis/bio_2.htm). So it would be a lot easier to replace skin cells than losing brain cells, which could be a permanent loss. Without enough cells to function properly, that system would not function well, subsequently harming the ability of the human to survive.
Looking at skin cells, it is important for skin cells to be constantly renewed because that is our outer protection that faces many environmental stresses. For example, if some UV rays killed some of our skin cells, it would not be good if our cells did not continue to divide and replace the dead cells because we would be left with non-functional cells that we need to protect ourselves. Also, the continuous division of skin cells keeps our skin smooth; however, as we get older, our “skin produces less collagen” so our skin become less elastic (http://cancerj10.imascientist.org.uk/2010/06/how-come-skin-goes-wrinkly-as-you-get-older). In addition, our skin becomes thinner, and good ole gravity helps pull our skin down, producing wrinkles (http://cancerj10.imascientist.org.uk/2010/06/how-come-skin-goes-wrinkly-as-you-get-older).
To wrap things up, humans have many different cell types unlike bacteria and each cell type must be present for the human to function as a whole. Some human cells are constantly being renewed, whereas other cells do not undergo reproduction. Cell division is necessary for all cells at some point in the human development, but problems can occur. The cell cycle is regulated by checkpoints to make sure that each cell is dividing how it should, but sometimes cells ignore the cell cycle regulations and divide unchecked; these cells are known as cancer cells.
(Bobby Muttilainen, rmuttilainen@gmail.com)