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病毒与受体的发展 已有1人参与
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细 胞作为一个独立的生命体系，为什么会发展出一些受体，以主动的形式接纳一个准备消灭自身的病原体? 求系统的解释 参考文献《分子病毒学》 |
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Jianxiao_H
金虫 (正式写手)
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万木有灵(dllchina代发): 金币+2, 鼓励热心应助 2014-08-09 08:53:59
感谢参与，应助指数 +1
万木有灵(dllchina代发): 金币+2, 鼓励热心应助 2014-08-09 08:53:59
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Long before multicellular organisms appeared on Earth, unicellular organisms had developed mechanisms for responding to physical and chemical changes in their environment. These almost certainly included mechanisms for response to the presence of other cells. Evidence comes from studies of present-day unicellular organisms such as bacteria and yeasts. Although these cells largely lead independent lives, they can communicate and influence one another’s behavior. Many bacteria, for example, respond to chemical signals that are secreted by their neighbors and increase in concentration with increasing population density. This process, called quorum sensing, allows bacteria to coordinate their behavior, including their motility, antibiotic production, spore formation, and sexual conjugation. Similarly, yeast cells communicate with one another in preparation for mating. Cells in multicellular animals communicate by means of hundreds of kinds of signal molecules. These include proteins, small peptides, amino acids, nucleotides, steroids, retinoids, fatty acid derivatives, and even dissolved gases such as nitric oxide and carbon monoxide. Most of these signal molecules are released into the extracellular space by exocytosis from the signaling cell. Some, however, are emitted by diffusion through the signaling cell’s plasma membrane, whereas others are displayed on the external surface of the cell and remain attached to it, providing a signal to other cells only when they make contact. Transmembrane proteins may be used for signaling in this way; or their extracellular domains may be released from the signaling cell’s surface by proteolytic cleavage and then act at a distance. Regardless of the nature of the signal, the target cell responds by means of a receptor, which specifically binds the signal molecule and then initiates a response in the target cell. In most cases, the receptors are transmembrane proteins on the target cell surface. When these proteins bind an extracellular signal molecule (a ligand), they become activated and generate various intracellular signals that alter the behavior of the cell. In other cases, the receptor proteins are inside the target cell, and the signal molecule has to enter the cell to bind to them: this requires that the signal molecule be sufficiently small and hydrophobic to diffuse across the target cell’s plasma membrane. However, these receptors which play a significant roles in cell communication also can bind to pathogenic microorganisms due to a very low coincidence. Once the virus, for instance, enters a cell, it replicates and mutates. At the same time, by the natural selection, favourable mutations will develop. |
2楼2014-08-07 11:19:16
3楼2014-08-08 19:48:18
Jianxiao_H
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Well, I have to say that it's a really complex. When I studied virology via videos provided by the Columbia University Internet course, something aroused my interest. The professor was asked, from my perspective at least, a very interesting question: do they (scientists) think that bacteria evolve before the viruses or more they later than that. The professor responded: it depends on who you ask, you'll get both answers. Yes, some people believe in "organic soup" theory, others don't. Yet we haven't found any solid evidences in years of evolution to testify whether it's right. But they do have something in common. So, I hardly think that the cell produces some specific receptors to recognize the virus and provide a beneficial condition for them. Namely, the virus and cell share a biological system. To be exact, cell's replication and expression system does work for viruses, and then the virus survives. For the last question, you can check out this website: http://v.163.com/movie/2010/7/N/8/M84FN47JJ_M84IQKLN8.html |
4楼2014-08-09 00:29:21
Jianxiao_H
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5楼2014-08-09 00:31:51
6楼2014-08-09 10:00:30
7楼2014-09-04 21:18:05
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