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Current time:0:00Total duration:5:01

Subviral particles: viroids and prions

Video transcript

let's talk about sub viral particles they're called sub viral particles because they're smaller than viruses and one thing to keep in mind is that viruses and sub viral particles together are all categorized as nonliving infectious agents and this is a mouthful but let's break it down again the nonliving part should be review for you now because viruses as we know are a cellular they're only made of a protein coat or a capsid which protects the genetic information which is DNA or RNA and sometimes a lipid envelope which I haven't drawn here because not all viruses have that envelope and because they're a cellular they're so small that they don't have organelles and that means they can't make their own energy which means ATP and they also can't divide or reproduce on their own and in order to do these two things it means that a virus needs a host so we've recent and that's why it's called nonliving and because they need a host they're infectious agents so you might be thinking well I know that about viruses so what are sub viral particles and how do they share those same traits well let's talk about them now there are two types of sub Bible particles viroids and prions and v roads are smaller than viruses because they're only made of a single strand of circular RNA up until very recently they were pretty much only found to infect plants which i hope you can remember because i've written this in green and i've drawn this funky little bush thing on top of some grass and today v roids have been found in humans in the case of hepatitis D so how do V roids make more of themselves if they only are made of circular RNA well you can think of this in terms of C's because it's thought to be catalytic RNA so c4 catalytic and c4 circular and catalytic RNA means that it can make or break covalent bonds another C and because it can do that it can self cleave to create more V Rhodes now there's one thing to really pay attention to you don't want to confuse Bureau Ed's with very ons because very ons are what we call whole viruses that means the protein coat plus the RNA or maybe an envelope because once a virus gets inside of a host and the protein coat falls off it's only genetic material at that point DNA or RNA so that helps distinguish between a virus outside of a cell and a virus inside of a cell so remember V roids and Furion's are different and now let's talk about prions which are kind of funky they actually were very recently discovered because scientists have always argued about whether or not proteins can be infectious by themselves prions come from the word pro tenacious infectious particles and I know that Pro in is not prion but they jumbled up the oh and the eye to make prion and prions have no genetic material that means no RNA or DNA at all they are only made of proteins so a normal protein is generally in the shape of an alpha helix well a prion protein which we'll call PRP prion protein tends to be in a beta sheet conformation so to be completely honest we don't really know that much about prions but it's thought that because these two proteins the prion protein and the normal protein are made of the same amino acids they are the same protein but in a different shape when the beta sheet comes in contact with the alpha helix it will change the alpha helix to a beta sheet and as more and more of these alpha helixes become beta sheets this creates protein deposits and which is already a bad thing but if it happens somewhere like the brain normal clean up still happens so these protein deposits will be cleaned up and that would actually leave huge holes in your brain as the proteins are removed causing disease and again prions are different from viruses and viroids because as we know them now they are only proteins and do not have any genetic information