HIV Flashcards
What is AIDS caused by?
HIV.
What are the structures of HIV and draw?
- On the outside is a lipid envelope.
- Attachment proteins are embedded within the lipid envelope.
- Inside the envelope is a protein layer called capsid.
- Inside the capsid, it encloses 2 strands of RNA and some enzymes.
- One of the enzymes is reverse transcriptase, it catalyses the produce from DNA to RNA and in reverse, it the catalysed by transcriptase, making DNA from RNA.
What group of viruses does HIV belong to?
Retroviruses.
How can HIV reproduce?
As a virus, HIV cannot reproduce by itself, it uses its genetic material to instruct the host cell’s biochemical mechanism to produce the component needed to make a new HIV.
How does HIV instruct the body’s mechanism to make new HIVs?
- From infection HIV entering the bloodstream and circulates around the body.
- A protein on HIV readily binds with a protein called CD4. This protein appears on many different types of cells, but HIV is most frequently attached to helper T-cells.
- The protein capsid fuse with the cell-surface membrane. The RNA and enzymes of HIV enter the helper T-cell.
- HIV reverse transcriptase converts the virus’s RNA to DNA.
- The newly made DNA is moved into the helper T-cell’s nucleus where it’s inserted into the T-cell’s DNA.
- The HIV DNA in the nucleus creates mRNA using the cell’s enzyme. This mRNA has the instructions for making new viral proteins and the RNA goes into the new HIV.
- The mRNA passes out of the nucleus through the nuclear pore and uses the cell’s protein synthesis mechanisms to make HIV particles.
- The HIV particles break away from the helper T-cells with a piece of their cell-surface membrane which forms their lipid envelope.
How does HIV cause AIDS?
HIV specifically attacks helper T-cells, so HIV causes AIDS by killing or interfering with the normal functioning of helper T-cells.
A normal person might have 800-1200 helper T-cells in each mm3 of blood whereas an infected person might only have 200.
Without enough helper T-cells, the immune system cannot stimulate B cells to produce antibodies or cytotoxic T cells. Memory cells can also be infected or destroyed so the body cannot produce an immune response and becomes vulnerable towards other infections and cancers.
What does ELISA stand for?
Enzyme linked immunosorbant essay.
What does the ELISA test do?
It uses antibodies to detect the presence of proteins in a sample and its quantity. It is extremely sensitive so it can detect even the smallest amount of molecules.
How does the ELISA test work?
1) Apply the sample to a surface e.g. a slide, so the presented antigens will attach.
2) Wash the surface several times to remove any unattached antigens.
3) Add the antibody that is specific to that antigen and leaves them to bind.
4) Wash the surface to remove any excess antibodies.
5) Add a second antibody that will only bind with the first antibody. This second antibody has an enzyme attached to it.
6) Add the colourless substrate that is complementary to the enzyme. The enzyme will act upon the enzyme and change into a coloured product.
7) The amount of antigen present depends on the intensity of colour that develops.
How can HIV be detected?
By the ELISA test.
What can the ELISA test test for other than HIV?
The concentration of a drug and allergens.
Why antibiotics are ineffective against viral diseases e.g. AIDS?
Antibiotics work against bacterial cells by inhibiting certain enzymes that are needed for making and assemble the peptide cross-linkages in bacterial cell walls so it would weaken the cell wall. As water enters bacterial cells by osmosis, it would usually be controlled by the cell walls, but through the work of antibiotic, the cell walls cannot withstand the pressure of osmosis, therefore, the cell bursts and the bacterium dies.
However, viruses rely on host cells to carry out their metabolic activities, therefore, they don’t have their own metabolic pathways and cell structures. So antibiotics are ineffective because there are no metabolic mechanisms to disrupt and viruses have a protein coat rather than a murein cell wall so there are no sites for them to work on. Therefore, as viruses are within the organism’s own cells, antibiotics cannot reach them.
