HIV

Structure of the human immunodeficieny virus:

• On the outside is a lipid envelope, embedded in which are attachment proteins
• Inside the envelope is a protein layer called a capsid that encloses two single strands of RNA and some enzymes
• One of these enzymes is called reverse transcriptase, so called because it catalyses the production of DNA from RNA
• The presence of reverse transcriptase and consequent ability to make DNA from RNA means HIV belongs to a group called the retroviruses

Replication of HIV:

• HIV does not replicate itself
• Uses genetic material to instruct the host cell's biochemical mechanisms to produce the components required to make new HIV
• Following infection HIV enters the bloodstream and circulates around the body
• A protein on the HIV readily binds to a protein called CD4
• HIV most frequently attaches to helper T cells
• The protein capsid fuses with the cell surface membrane
• The RNA and enzymes of HIV enter the helper T cell
• The HIV reverse transcriptase converts the virus's RNA into DNA
• The newly made DNA is moved into the helper T cell's nucleus where it is inserted intothe cell's DNA
• The HIV DNA in the nucleus creates messenger RNA using the cell's 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 cell's protein syntheis mechanisms to make HIV particles
• The HIV particles break away from the T helper cell with a piece of its cell-surface membrane surrounding them which forms their lipid envelope

How HIV causes the symptoms of AIDS:

• Killing or interferring with the normal functioning of helper T cells
• Without…