BIOLOGY - HIV

- HIV enters the blood stream

- HIV attachment proteins bind to proteins on the cell surface membrane of a helper T cell

- the capsid fuses with the cell surface membrane of the helper T cell

- the contents of the capsid (HIV RNA, reverse transcriptase) enter the helper T cell

- reverse transcriptase makes a DNA copy of the HIV RNA

- the HIV DNA is joined to the host cell's DNA

- the DNA is used to make copies of HIV RNA, enzymes, proteins, capsids at the host cell's ribosomes

- these copies are used to make new HIV particles

-new HIV particles bud off from the cell surface membrane of the host cell, using it as a lipid envelope which causes the host cell to rupture and die

- HIV specifically attacks helpter T cells

- destruction of helper T cells means there is less of it in the blood

- people with HIV are classed as having AIDS iwhen they suffer from the symptoms of a failing immune system and if their helper T cell count is below a certain number

- helper T cells can't activate B cells

- no antibodies or cytotoxic t cells are being produced

- body can't fight of infections and/or cancers

- person dies from infections or cancers rather than from HIV

- only effective against bacteria

- in bacterial cells, water is constantly entering by osmosis. the cell wall is made of murein which is a strong material and this prevents the cell from bursting.

- antibiotics inhibit the metabolic pathways and enzymes involved in the formation of peptide cross-linkages 

- lack of peptide cross-linkages makes the cell wall unable to resist the pressures of osmosis so the cell bursts

- viruses don't have a cell wall

- viruses replicate inside a host cell. antibiotics can't get inside hhost cells

- viruses use the metabolic pathways of the host cell

- there is no current cure or vaccine

- antiviral drugs can be used to slow down the progress of HIV infection and AIDS

- best way of controlling is reducing its spread. it spreads by:

          - unpotected sex

          - contact with infected bodiy fluids

          - blood transfusion from a person with HIV

          - HIV positive mother to fetus