Cell Recognition and the Immune System- HIV and Viruses Flashcards
What can HIV cause?
AIDS
What is HIV (human immunodeficiency virus?
A virus that affects the immune system
What is AIDS (acquired immune deficiency syndrome)?
A condition where the immune system deteriorates and eventually fails, which makes someone with AIDs more vulnerable to other infections
How does HIV infect cells?
HIV infects (and eventually kills) helper T cells (host cells) until there aren’t enough cells for an effective response to infections
When do people with HIV develop AIDS?
When the helper T cells reach a critically low level
What is the structure of HIV?
- A core that contains RNA and reverse transcriptase needed for virus replication
- Outer coating of protein called a capsid
- Extra outer layer called an envelope
- Attachment proteins sticking out from envelope
How does HIV replicate?
- Attachment protein attaches to receptor molecule on cell membrane of host helper T cell
- Capsid released into the cell and it uncoats and releases genetic material into cytoplasm
- Reverse transcriptase used to make a complementary strand of DNA from viral RNA template
- Double-stranded DNA made and inserted into human DNA
- Host cell enzymes used to make viral proteins from viral DNA found within human DNA
- Viral proteins assembled into new viruses which bud from cell and infect other cells
When are people with HIV classed with having AIDS?
When symptoms of their failing immune system start to appear or their helper T cell count drops below a certain level
What are initial symptoms of AIDS?
Minor infections of mucous membranes and recurring respiratory infections
What happens as AIDS progress?
The number of immune system cells decreases further and patients become susceptible to more serious infections
What happens during the late stages of AIDS?
Patients have a very low number of immune system cells and can develop a range of serious infections that kills AIDS patients
How do antibiotics kill bacteria?
Interfere with their metabolic reactions, they target bacterial enzymes and ribosomes used in these reactions
How are antibiotics designed to target only bacterial cells?
Bacterial enzymes and ribosomes are different from human enzymes and ribosomes so they don’t damage human cells
Why can’t antibiotics inhibit viruses?
Viruses don’t have their own enzymes and ribosomes as they use the ones inside the host cells and antibiotics don’t target human processes so can’t inhibit them
How are antiviral drugs designed?
To target the few virus-specific enzymes that exist
