Describe the life cycle of HIV

A HIV molecule enters the blood stream and invades cells of the immune system (CD4 cells). To do this, proteins on the surface of the virus bind to receptors on the host cell. This then allows the envelope of HIV to fuse with the cell membrane of the host cell, allowing the contents of the HIV molecule to enter the host cell. This includes RNA (the genetic material of HIV) and the HIV enzymes - reverse transcriptase and integretase. Now inside the host cell, the HIV uses its reverse transcriptase enzyme to convert the HIV RNA into HIV DNA. This HIV DNA can then enter the host cell nucleus and be integrated into the host's DNA with help from the HIV integrase enzyme. As HIV DNA is now integrated into the host DNA, it uses the host's transcription machinery to produce more HIV proteins. These HIV proteins then move towards the cell surface where they 'bud', forming new molecules of HIV as they burst out of the host cell, killing it in the process.