2C - HIV and viruses Flashcards
What is HIV?
A virus that affects the immune system and the virus that causes AIDS.
What does HIV stand for?
Human immunodeficiency virus.
What does AIDS stand for?
Acquired immune deficiency syndrome.
What is AIDS?
A condition where the immune system deteriorates and eventually fails.
How does HIV work?
HIV infects (and eventually kills) Helper T-cells, which act as host cells for the virus. Without helper T-cells, the immune system is unable to mount an effective response to infections because other immune system cells don’t behave how they should.
When do people with HIV develop AIDS?
When the helper T-cell numbers in their body reach a critically low level.
What can attachment proteins also be called?
Envelope proteins.
Describe the structure of HIV
A core contains the RNA and some proteins including the enzyme reverse transcriptase which is needed for virus replication.
An outer coating of protein - capsid.
An extra outer layer called a lipid envelope made of membrane stolen from the cell membrane of a previous host cell.
Loads of copies of an attachment protein sticking out from the lipid envelope that help HIV attach to the host helper T-cell.
What enzyme does HIV have and what does it do?
Reverse transcriptase needed for virus replication.
How does HIV replicate?
- HIV infects body and goes around bloodstream.
- Comes across cell with CD4 protein which is usually found on Th cells.
- The attachment proteins are complementary to CD4.
- It binds to Th cell.
- The capsid fuses with the cell membrane allowing the RNA and transcriptase enzyme to enter cells.
- Reverse transcription takes place converting RNA to DNA (retrovirus).
- The RNA (viral) moves into nucleus and integrates with its DNA.
- This triggers messenger RNA to code for proteins (mRNA).
- This moves out of nucleus.
- Uses the cells organelles to replicate and make its proteins.
- The proteins allow the virus to assemble.
- It then breaks away from host cell.
- We struggle to detect it because it breaks away with parts of the Th cell membrane.
Why does our body struggle to detect HIV cells?
Because it breaks away with parts of the Th cell membrane when it replicates.
What is the length of time for HIV to develop into AIDS?
Usually around 10 years.
What are the initial symptoms of AIDS?
Minor infections of mucous membranes and recurring respiratory problems.
What happens as AIDS progresses?
Patients become susceptible to more serious infections including chronic diarrhoea, severe bacterial infections and tuberculosis.
What happens during the late stages of AIDS?
Patients can develop a range of serious infections such as toxoplasmosis of the brain (a parasite infection) and candidiasis of the respiratory system (fungal infection).
