hello and welcome to learn a level biology for free with mr. ik in this session we're gonna be going through the structure of HIV and the replication and symptoms of AIDS make sure you got yourself a pen and paper in case you want to make notes as you go through pause the video any point to help you with that and to make sure you got sound on so first of all just the viral structure in general viruses aren't considered living cells they have to replicate replicate inside of the host cell and that's one of the reasons why viruses are hard to treat with medicine because in order to destroy the viral cell you'd have to destroy the host cell as well the other reason is why antibiotics specifically won't destroy a viral cell is antibiotics will interfere with mechanisms such as protein synthesis or respiration or the cell wall pause and the bacteria will have particular mechanisms that the antibiotics will direct the attack or interrupt whereas the viruses don't have those same membrane bound organelles and also they don't have the same chemical reactions so therefore the antibiotics aren't effective against them the structure is more basic so they have the protein envelope a protein capsid and within that they have their genetic material which can be DNA or RNA and HIV is one of the viruses which has RNA so the structure of HIV you would need to know and the key things you need to know about structure are first of all the core and that is made up of RNA as the genetic material and then the enzyme reverse transcriptase and both of these are needed for viral particles to be able to replicate inside of the host cell it has an outer protein coat which is shown here in orange that is the capsid so that is our protein layer the envelope around the outside is actually made up of the hosts cell membrane so though we do have that lipid membrane that is taken from the host cells and then final part we can see is these protein attachments and those are how the HIV particle is able to attach to the helper T cells so next n is looking at how HIV replicates inside of its host and if we think about the host we're going to think about the human as our host and the first thing that happens is that HIV particles will be transported around in the blood of the human and within the blood you also have the helper T cells a type of white blood cell and the protein attachment on the HIV cell is able to attach to what we call the cd4 protein on a helper T cell so once it's then attached the next part happens is the membrane from the HIV fuses with the membrane of the helper T cell and when it fuses the enzyme so the reverse transcriptase and the RNA are released into that white blood cell the helper T cell once the RNA and the enzymes are then within the white blood cell that HIV enzyme reverse transcriptase can then turn the RNA the viral RNA into copies of DNA and that DNA can then move into which we've seen here move into the nucleus of the helper T cell and that is then how we get new particles of our H of HIV being replicated and as it does this it destroys the helper T cell and that's actually the damage that HIV is causing it's destroying the helper T cells so symptoms of a HIV within the first couple of weeks often flu-like symptoms a fever high temperature my rash my fake swollen glands and that is linked to the idea these helper t-cells being destroyed the symptoms of AIDS are far more severe so if you are HIV positive that means you have four HIV virus within your body it's classed as Apes when the replicating virus is in helper T cells have destroyed so many helper T cells that it's interfering with the normal functioning of so with the helper T cells being destroyed by the replicating HIV virus the host in this case the human is unable to produce an adequate immune response and that's why they are vulnerable to infections and cancer and it is the destruction of the immune system which leads to death rather than the HIV directly so in summary viruses replicate inside of the host cells and cannot be destroyed by antibiotics the specific structure of HIV consists of a core which is made of RNA and enzyme reverse transcriptase it has a capsid out of protein coat and an envelope made of the host cell membrane and protein attachment HIV attaches to a cd4 protein on health t-cells when it does that it's envelope can fuse with the helper T cell and that releases in the enzyme reverse transcriptase and the viral RNA and once inside of the helper T cell DNA copies can be made and that will then result in the replication of the HIV causing helper T cells to be destroyed and with the helper T cells being destroyed the host is unable to produce an adequate immune response and that is why the host is left vulnerable to infections and cancer so the final thing just to point out that when the replication virus is in the helper T cells interfere with the normal function of the immune response that is when it's classed as AIDS and HIV positive just means you have the HIV virus inside of the host so that covers what you need to know about HIV for a QA level biology if you do want to practice will test your knowledge then go to miss Esther ich komm to find questions on this topic and I'll link it in the description below if you haven't already subscribed make sure you do click on the button to subscribe to keep up to date with all the latest videos