1. ARE viruses alive?
To discuss whether the viruses are alive or not, we need to know the definition of lives first. Unfortunately, there is no precise definition to separate the living and non-living. In my opinion, there are two factors, which are the most important criteria, to determine the existence of lives. The first one is self-awareness, which means the ability a living thing has to move and response to outer environment. In this sense, viruses are not alive since it neither can move nor react to simulation. On the other hand, viruses can be considered alive under certain circumstances. Another criterion for defining lives would be the ability to pass genetic information into future generations. In this case, viruses are undoubtedly alive since they can produce themselves by attacking host cells.
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However, I don’t like an uncertain answer for this question, so I generate my own thoughts to explain it. First of all, we need to take a look at viruses’ structure. They have either DNA or RNA as genetic materials and a “protein coat” called capsid, and……that’s it! Viruses are not composed of cells therefore they do not belong to any Domain. When we split viruses apart, there is nothing except proteins and DNA or RNA, which are definitely not forms of life. However, when we do the same thing to dissect those undoubted living creatures such as human, the stuff we get from decomposition will also be different kinds of molecules, which are considered non-livings. The only difference is that the molecules compose a human are far more than those of a virus. In other words, humans are just more complicated than viruses. Consequently, it makes no sense to define humans as living things while viruses are not!
Nevertheless, I realized that creatures’ composition is not a simple calculation like adding, subtracting or splitting apart. The different ways of molecular combination result in totally unique things. Cells are the key. The cooperation of varieties of cells which compose our body make us capable to do way more things that viruses can’t. The cells make us more complicated, they make us ALIVE.
2. Why the infected individual is never cured and has repeated outbreaks
A common sense tells us when a new kind of virus tries to break through our immune system, our strong body can always beat them and produce a specific kind of antibody to protect us from being infected by this virus again. Vaccine, a great invention that has saved uncountable lives, is based on this theory.
Nevertheless, antibody and vaccine do not always work. Similar to organisms’ evolution, there must be variations occur when new forms of virus are expected. The evolution of organisms happens rarely and slowly, which is a process that is often estimated to take over thousands of years. However, viruses evolve much more frequently. Moreover, most of the results after viruses evolved are harmful to humans, explaining why repeated outbreaks occur to single individual for multiple times.
Nevertheless, antibody and vaccine do not always work. Similar to organisms’ evolution, there must be variations occur when new forms of virus are expected. The evolution of organisms happens rarely and slowly, which is a process that is often estimated to take over thousands of years. However, viruses evolve much more frequently. Moreover, most of the results after viruses evolved are harmful to humans, explaining why repeated outbreaks occur to single individual for multiple times.
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In viruses’ lytic infection, a new generation of viruses can be produced within only 5 steps. Also, being taken over by a virus, a single infected cell can produce as many as 10,000 virus particles. The large amount of offspring and the negligible time required to make them create many chances for new mutants to be formed. Therefore, changing frequently, viruses can always outsmart our bodies’ defence and get us ill repeatedly.
3. How does your body defend against pathogens such as bacteria and viruses?
After the discovery of microscope, humans finally realized that there are much more organisms living around us than we could ever expect. The reason that we could not discover them sooner is because they are too tiny to see, yet they live right on the outside or inside of our bodies. Although most of them are harmless, the others can cause severe diseases if our bodies do not defend them appropriately. So, how do our bodies defend these pathogens?
1) Phagocytosis
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White Blood Cells in human immune system are good examples of Phagocyte. A phagocyte can recognize the chemical signal that released by bacterium, leading itself towards the harmful bacterium and attaches to its cell membrane. Engulfing the bacterium, the phagocyte can now digest it using the enzymes.
2) immune system response
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Interferon
Interferon is a kind of protein produced by the infected cells that can warn other cells and activate the immune system to response to the potential invaders. To clarify it scientifically, its real function is to stimulate the host cell and the nearby cells to produce certain kinds of protein which can prevent the replication within them.
Interferon is a kind of protein produced by the infected cells that can warn other cells and activate the immune system to response to the potential invaders. To clarify it scientifically, its real function is to stimulate the host cell and the nearby cells to produce certain kinds of protein which can prevent the replication within them.
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Antibodies
Have you wondered how immunization works inside your body? It works because a type of protein built by B cells (a kind of cell in immune system) defend them before you get sick. Once antigens enter into a human body and attach to B cells, B cells begin to divide and mature, allowing them to carry large amount of antibodies. Antibodies have the ability to attach the antigens, clump them together and immobilize them, making them easy to be destroyed by the phagocytes. Due to the existence of antibodies in your body, you will never get infected by same viruses or bacteria twice.
Have you wondered how immunization works inside your body? It works because a type of protein built by B cells (a kind of cell in immune system) defend them before you get sick. Once antigens enter into a human body and attach to B cells, B cells begin to divide and mature, allowing them to carry large amount of antibodies. Antibodies have the ability to attach the antigens, clump them together and immobilize them, making them easy to be destroyed by the phagocytes. Due to the existence of antibodies in your body, you will never get infected by same viruses or bacteria twice.
4. Explain three methods bacteria can use to alter its genetic information.
1) Transduction
In my opinion (which is just a thought and might not be right), the reason why that viruses can change so rapidly is that viruses have much less genetic materials than other more complex organisms, allowing a tiny genetic mutation to cause a real big change. The first method that bacteria use to change their DNA or RNA has to do with viruses' mistake during copying themselves.
Transduction is the process happens when a bacteriophage injects its genetic material into a bacterium and starts to replicate itself. However, instead of replicating identical new viruses, some mistakes may occur and result in some new viruses with host cell genetic material in them (which is supposed to be viral genetic material). The new viruses with mistakenly placed genetic material will go on and infect other bacteria, spreading the host cells' genetic material instead of his own. This process will therefore change the following infected bacteria's genetic material.
Transduction is the process happens when a bacteriophage injects its genetic material into a bacterium and starts to replicate itself. However, instead of replicating identical new viruses, some mistakes may occur and result in some new viruses with host cell genetic material in them (which is supposed to be viral genetic material). The new viruses with mistakenly placed genetic material will go on and infect other bacteria, spreading the host cells' genetic material instead of his own. This process will therefore change the following infected bacteria's genetic material.
2) Conjugation
Compared with Transduction, Conjugation is a much more direct way to change bacteria's genetic material. In Conjugation, a small circular piece of DNA called Plasmid inside bacteria plays an important role. It is separate from the chromosomal DNA. During the process, an F+ cell and an F- cell will tend to fuse together and allow a strand of plasmid DNA transferred from F+ cell to the F- cell. After the transfer, both F+ cell and F- cell will synthesize a complementary strand, making the F- cell a F+ cell, and restoring the original F+ cell to complete its plasmid.
3) Transformation
Transformation is a process that results alteration in bacterial genetic material. It is as simple as the graph shown above. The bacteria may take in or incorporate with the surrounding genetic materials produced by others through cell membranes. The exogenous genetic material will be inserted inside the original bacterial chromosomes, and therefore alter the bacterial genetic information.
5. Explain the evolution of antibiotic resistance. how is our use of antibiotics contributing to the development of "superbugs"?
When Alexander Fleming first identified antibiotics from fungi back in 1929, a revolution of medicine begun. Beyond people's expectation, an arm race between human and bacteria also silently started at the same time.
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Bacteria reproduces like crazy, they can produce a whole new generation within 20 minutes. Therefore, mutations occur much more frequently on bacteria than those occurred on humans (who reproduce every 25 years or so). The consequence of this would be a larger variety of bacteria and beneficial traits for bacteria to protect themselves. Sounds familiar, huh? This reminds us of Darwin's theory of evolution! Which means natural selection also applies to these unicellular prokaryotes. However, who would be the biggest "predator" of bacteria? Is that disinfectant? Or......ANTIBIOTICS!
Although bacterial mutation rate is already fast enough, the presence of antibiotics even accelerates the speed. Due to the beneficial mutations occurred normally, some bacteria may have antibiotics resistance. Hence, they can resist the attack from antibiotics while other bacteria without the ability would be killed. In this process, the antibiotics that people take in enforces the mechanism of natural selection, killing the weak ones while keeping the fit ones alive. Before long, the antibiotics resistant bacteria may occupy a large portion within ones' bodies, weakening the efficiency of antibiotics. Also, transduction, conjugation, and transformation, the methods bacteria use to alter their chromosomes would increase the number of them having resistant ability.
Undoubtedly, antibiotic resistance would be a tough yet necessary problem for human beings to overcome as soon as possible. The deficiency of antibiotics may retrogress our medicine technology back to 1920s. In the future, "Antibiotic Resistance" would be a familiar term for everybody on this planet, yet we are not even close to catch them in this deadly arm race.
Undoubtedly, antibiotic resistance would be a tough yet necessary problem for human beings to overcome as soon as possible. The deficiency of antibiotics may retrogress our medicine technology back to 1920s. In the future, "Antibiotic Resistance" would be a familiar term for everybody on this planet, yet we are not even close to catch them in this deadly arm race.