• Question: How does the structure of a virus help attack cells?

    Asked by anon-244767 on 29 Apr 2020. This question was also asked by anon-256666.
    • Photo: Emily Graves

      Emily Graves answered on 29 Apr 2020:

      Most viruses are made up of three parts: their genomic information (DNA or RNA), this is surrounded by a protective protein layer called the capsid, and an outer layer called the envelope (although not all viruses are enveloped).

      Viruses display different molecules on their surface which help them to attach to the surface of cells. These will only stick to specific molecules, called receptors, which are found on certain cells. The receptor that each virus will bind varies depending on what molecules the virus expresses. This is why viruses cause many diseases as they will attack different parts of the body through their binding to different receptors on certain cell types.

      Once the virus has attached itself to a cell it will be taken into the cell body. This is where the viral genetic information is copied by the cell and the viral genes are expressed to form new viral proteins. These proteins can then come together to form new virus particles which are released from the cell and can go onto attack more of the surrounding cells.

    • Photo: Sandra Greive

      Sandra Greive answered on 30 Apr 2020:

      A virus is a bit like a parcel where the box, or wrapping, protects the contents and the address on the outside directs it to the right place. A virus particle or “virion” is basically a container that protects the virus genes as it is spread to a new cell. This can either be in the same organism, like a plant or animal, or completely different one. The outside of the virus is covered with protein molecules that are unique to that type of virus. Different proteins have different shapes. So the shape of the proteins on the outside of the virus will match the shape of their partner protein on the outside of the target cell. This partner protein is called a receptor, because it receives the incoming virus protein. You can think of this process like the pieces of a 3D jigsaw puzzle fitting together. Once these shapes have ‘clicked’ into place in exactly the right way, the virus can enter the cell and unwrap the genes ready to make new viruses. If the shapes fit perfectly, the infection process is highly efficient, however, as the shapes begin to fit less well, the process becomes less efficient. If they don’t fit at all the virus can’t enter that cell. This is why viruses can only enter cells that have their receptor protein on the surface.

      The virus genes, or genome, (which can be either RNA or DNA) have all the information, or plans, needed to tell the machines (like the ribosomes that make new proteins) of the infected cell how to make all the parts needed to build lots of new viruses, and then how to assemble them. These new viruses are then spread to other cells which have the receptor on their outside surface.

    • Photo: Marta Dazzi

      Marta Dazzi answered on 30 Apr 2020:

      During a viral infection, viruses reproduce by hijacking your body’s cells. First the virus recognises the host cell. It does this by binding its proteins to specific receptors on the cell surface. If the cell does not have those specific receptors, it cannot be infected by the virus. Viruses surrounded by an “envelope” can fuse with the cell membrane. Enveloped and non-enveloped viruses’ can also trick the cell into taking them in through bulk transport (more specifically called endocytosis) of the cell. Once the genetic material of the virus has entered the cell it can replicate. The machinery for replication is provided by the host cell! The genes are also expressed to make viral proteins. These viral proteins can be used to surround genetic material, to create new viral particles.

      Once assembled, the viral particles are released from the living cell. It can do this by making the host cell burst (a method called lysis) and results in cell death. Other methods ensure the cell remains alive so that it can continue acting as a virus factory. For example, the new viruses can exit using the cell’s own transport pathways (exocytosis) or via a process called “budding”. During budding the virus fuses into the cell membrane, taking a part of it with them to form the viral envelope. Once escaped, the viruses can go and infect other cells!

    • Photo: Cameron Stockwell

      Cameron Stockwell answered on 19 May 2020:

      Viruses have proteins on their surface which allow them to bind to a cell and enter it allowing infection. When the viruses bind to the cell and enter they release their RNA (genetic material). This RNA allows the virus to make more versions of itself and use the host cell to make more virus.

      This RNA encodes more proteins that either allow the virus to replicate itself, or assemble more viruses to go on and infect more cells.