5.7 - The Human Immunodeficiency Virus (HIV) Flashcards
What is the structure of HIV?
- on the outside is a lipid envelope, embedded in which are peg - like attachment proteins
- inside the evolve is a protein layer called the capsid that encloses two single strands of RNA and some enzymes
What is the main enzyme called in HIV?
Reverse transcriptase
What does reverse transcripsase do?
Is catalyses the production of DNA from RNA - the reverse reaction to that carried out by transcriptase
Becasue of reverse transcripsase what group of viruses does HIV belong to?
Retroviruses
Becasue HIV is a virus what cant it do?
Replicate itself
How does HIV replicate then?
It uses genetic material to instruct the host cells biochemical mechanisms to produce the components required to make new HIV
What are the first half of steps of HIV replicating?
- Following infection HIV enters the bloodstream and circulates around the body
- A protein on the HIV readily binds to a protein called CD4. While this protein occurs on a number of different cells, HIV most frequently attaches to helper T cells
- The protein capsid fuses with the cell surface membrane. The RNA and enzymes of HIV enters the helper T cells
- The HIV reverse transcriptase converts the viruses RNA into DNA
What are the last steps of HIV replication?
- The newly made DNA is moved into the helper T cell’s nucleus where it is inserted into the cells DNA
- The HIV DNA in the nucleus creates mRNA using the cells enzymes. This mRNA contains the instructions for making new viral proteins and the RNA to go into the new HIV
- The mRNA passes out of the nucleus through a nuclear pore and uses the cells protein synthesis mechanisms to make HIV particles
- The HIV particles break away from the helper T cells with a piece of its cell surface membrane surrounding them which forms there nuclear envelope
Once infected by HIV the person is then said to be what?
HIV positive
The replication of HIV often goes into dormancy and only recommences when what?
When it leads to AIDS, many years later
How does HIV casue AIDS?
By killing or interfering with the normal functioning of helper T cells
How is without the sufficient amount of helper T cells bad?
The immune system cant stimulate B cells to produce antibodies or the cytotoxic T cells that kill cells infected by pathogens
Does HIV kill inderviduals directly
No - it effects the immune system meaning other infections cant be destroyed and so these infections therefore kill the individual.
What does ELISA stand for?
Enzyme linked immunosorbant assay
What does the ELIZA test do?
Allows you to tell if a particular protein, in this case a antigen is present in a sample
Give the first steps of the procedure of the ELIZA test
- Apply the sample to a surface, e.g a slide, to which all the antigens in the sample will attach
- Wash the surface several times to remove any unattached antigens
- Add the antibody that is specific to the antigen we are trying to detect and leave the two to bind together
- Wash the surface to remove any excess antibody
Give the last steps on the procedure of the ELIZA test
- Add a second antibody that binds with the first antibody. This second antibody has a enzyme attached to it
- Add the colourless substrate of the enzyme. The enzyme acts on the substrate to change it into a colours product
- The amount of antigen present is relative to the intensity of the colour that develops
