![]() ![]() A virus that kills the host will be less successful over time, compared to a virus which doesn’t harm the host. Yet, not all virus infections will be detrimental to the host. With the virus causing the common cold, the virus attacks respiratory cells and damages them as it does its work. This leads to a total loss of immune function in patients. The HIV virus, for instance, attacks immune cells exclusively. This causes a number of reactions, depending on which cells were infected. The biochemistry they evolved to live within the other species is not compatible with the new species, and cell damage and death occur. Most dangerous viruses have just recently jumped to a new species. Further, a virus tends to evolve with its host. In fact, the only reason a virus affects us at all is because it becomes active within our cells. Neither organism is active within their protective coat, they only become active when they reach favorable conditions. Scientists who support a virus being a living organisms note the similarity between a virus in a protein coat and a bacterial spore. The protein coat it exists in outside of a cell is the equivalent of a bacterial spore, a small capsule bacteria form around themselves to survive harsh conditions. Yet, by the definition of life laid out before, it seems that when a virus is inside of a host cell it does have all the machinery it needs to survive. They would say that a virus, without a host cell, cannot replicate on its own and is therefore not alive. Some people do not consider a virus living because a virus does not contain all of the mechanisms necessary to replicate itself. This is the process all life takes, where it is a single-celled organism or a multi-cellular organism. A cell is considered to be living because it contains all the necessary components to replicate its DNA, grow, and divide into new cells. Other virus molecules have even larger and more complex protein coats, and specialize on various hosts. In this way the virus can live within cells its entire existence, and never need a protein coat to protect it in the environment. When seeds are created within the plant, the virus spreads to the seeds. In some plant virus species, the virus is passed from cell to cell within the plant. ![]() Some virus molecules have no protein coat whatsoever, or have never been identified making on. The sheath and collar compress, puncture the cell, and deposit the DNA into the bacterial cell. The tail fibers grasp the bacterial cell, pulling the base plate up to the cell wall or membrane. ![]() ![]() The collar, sheath, base plate, and tail fibers are part of an intricate system to attach to and inject the genome into a bacterial cell. The head portion contains the viral genome. The protein coat of a phage is much more complex, and has a variety of specialized parts. The above image shows a phage, a type of virus which specializes on bacterial cells. While many virus particles take a simple shape like the one above, some are much more complicated. The replicated virus molecules will be packaged within their own protein coats, and be released into the environment to find another host. The protein coat can then be discarded, as the viral genome will now replicate within the host cell. Part of the protein coat will then open, puncture through the cell membrane, and deposit the viral genome within the cell. The various envelope proteins will enable the virus to interact with the host cell it finds. The above virus shows the typical structure a virus takes, a viral genome surrounded by a shield of proteins. The shape, structure, and function of these proteins changes depending on the species of virus. A virus which replicates in mammalian cells will have a protein coat which enables it to attach to and infiltrate mammalian cells. The exact structure of a virus is dependent upon which species serves as its host. Inside of the protein coat is a carefully folded RNA molecule, which contains the information necessary to replicate the protein coat, the RNA molecule, and the components necessary to hijack a cell’s natural processes to complete these tasks. Each virus looks like a little bent worm. Here, you can only see the protein coat of the Ebola virus. ![]()
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