Viruses, Viroids & Prions - Introduction to Biology - 11.9

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• published: 30 Jul 2015
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Visit: http://academyofone.org Forum: http://www.academyofone.org/forums/ Youtube: https://www.youtube.com/user/Academyofone1 Article: http://www.academyofone.org/virus-viroids-prions-introduction-to-biology-11-9/ Royalty free music licensed by http://www.stockmusic.net Royalty free photos licensed by http://www.bigstockphoto.com Script: So far in this unit, we talked about all the wonderful different kinds of life in this world. Well today we are going to give a nod to our non-living enemy... viruses. What’s going on everybody! My name is Jack Jenkins and this is Academy of One. Today we are talking about viruses as well as viroids and prions. The basic definition of a virus is a small non-living infective agent. Well that definition has a lot of meaning it for just a few words. Let’s flesh out the definition with some background information. The small part in that definition comes from the fact that a virus is incredibly small even when we are talking on a cellular level. A virus can be as small as thirty nanometers. For comparison, a red blood cell is around six thousand nanometers. These viruses are incredibly tiny. The second statement in the definition of a virus is the point that they are non-living. Well, why isn't a virus considered a living organism? Well first, viruses don't have any cells. The basic and smallest component of life is the cell. Viruses don't have any cells so by default they can’t be considered a living organism. Now here’s a question you all are probably thinking. If a virus is not made up of cells then what is it made up of? Well a virus is made up of two or three parts, depending on the virus. The first part is the hereditary molecule or molecules. This is either a single or double strand of DNA or RNA. The second part is a coat that is made up of proteins that surrounds the DNA or RNA. This protein coat is known as a viral capsid. The purpose of the capsid is to latch on to and penetrate cells. The capsid also aids in protecting the DNA or RNA some viruses, not all, have a third part which is a bilayer of lipids that surround the protein coat. The protein coat and lipid layer are known as the viral envelope. Again, some have this while others don’t. In Fact, as you can see from all the pictures I’ve been putting up viruses can be very different from each other. Giving each virus its own special characteristics. Another reason why viruses’ are not considered a living thing is because viruses can’t do anything by themselves. They don’t have any membrane so they can’t eat, can’t replicate, can’t make proteins... they can’t do anything. Viruses rely entirely on their host for living. This is why they are considered an infectious agent. They can only survive at the loss of another cell. For example, they can only reproduce inside of a cell because they don’t have any of the organelles needed for reproduction. In order to reproduce, the virus will hijack parts of the cell such as the ribosomes, amino acids and more to make more versions of itself. Those versions will then go to different cells and hijack there parts and make more of them so on and so forth. The problem is that the cell won’t be able to replicate itself and the virus will eat all of the cells food. This will literally kill the cell. With viruses being able to affect and kill cells rapidly you can see why viruses are such a threat to our lives. You can also see why when you get the flu it just hits you like that. The flu sucks. Since viruses are so closely tied to the host of the cell, viruses are incredibly hard to kill or get rid of. There are some antiviral medications but viruses adapt very easy. Viruses are very simple and lack any way to check there DNA or RNA so mutations happen to them very quickly. These mutations may help them get around the antiviral medications. This is why virus caused diseases like HPV are very hard to cure. Once you do come up with a cure the virus will mutate itself around the cure. We’ll talk about the medical difficulties of viruses as well as more general information on viruses in our upcoming course on virology. I should say before we jump to our other infectious friends is that not all viruses can go into every host. A virus that affects one person won’t affect another. Also there is no organism that is immune to all viruses. Every organism out there has at least one virus that hunts it like a bounty hunter