Tuesday, March 29, 2011
Cell recognition
On page 123-124, Shubin describes the cell's ability to recognize each other in order to form larger masses such as tissues or bodies. In between cells can lay different kidns of collagen and proteoglycans that help attach cells. What causes the cell to be able to recognize other cells to attach to each other? How does this communication relate to the function that the cells must perform in the body? Relate this ability to recognize other cells to the function of DNA in expressing genes.
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ReplyDeleteIn these passages, Shubin discusses the ability of the body cells to come together and form larger groups of cells, eventually becoming tissues and organs. The "materials" mentioned in the prompt provide structure and support for those groups of cells.
ReplyDeleteThe process of cell-to-cell recognition can be considered part the process that Shubin discusses. When considering the fluid mosaic model for cell membranes with the phospholipid bilayer, the mechanism employed by the cells to allow for recognition becomes clear. The membrane proteins embedded within the membrane serve this purpose. Specifically, glycoproteins serve as "identification tags" that are recognized by the membrane proteins of other cells (Campbell, 129). Cells recognize each other by binding to surface molecules, sometimes carbohydrates, on the plasma membrane. However, cell-to-cell recognition is a critical component of a functioning immune system. White Blood Cells can recognize body cells by the specific membrane proteins or carbohydrates that allow for proper identification. Foreign objects would not contain those same identifiers, thus the B-Cells and T-Cells can identify foreign objects and prevent infection (Campbell 936).
As certain genes are turned on or off, it is possible that certain proteins or carbohydrates in the membrane could be changed, completely altering how that cell would be recognized. These membrane glycoproteins and carbohydrates can help mark certain traits because they can identify different types of cells. A prime example is the variation of blood types. The variation in blood types is simply an alteration of the carbohydrates that are embedded in the plasma membrane (Campbell 130). If certain genes code for a certain carbohydrate or glycoprotein to be embedded within the membrane, a change in the DNA could cause a completely different identification.
Vickram Pradhan 1/2a
vickram.pradhan@yahoo.com
Vickram was right when he said that B-cells and T-cells identify foreign bodies. They do this with the use of major histocompatibility complexes (MHC) molecules. These molecules are divided up into two classes, Class I and Class II. The Class I molecules are the key to cell recognition. Every nucleated cell in the body has these proteins, and each person's Class I MHC molecules are unique. Of all the human genes (and 99.9% are shared among all humans), the MHC gene is one that differs slightly from person to person. Our macrophages and neutrophils have these molecules too (as all cells do) and can recognize other cells' MHC molecules. When these cells run into the rest of our cells, they bump into our Class I MHC molecules and everything is fine. When a foreign cell is introduced into our body (either bacteria or an organ transplant), our white blood cells do not recognize the MHC molecules and the cytotoxic cells attack, lysing the intruders. Also, when our body cells become infected or cancerous can "synthesize foreign antigens and display antigen fragments" (Campbell 938) on the cell's surface. This attracts macrophages to destroy the infected cell, maintaining homeostasis.
ReplyDeleteJeremy Solomon
imabum14@gmail.com