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AQA Biology - Unit 2C - HIV And Viruses
Terms in this set (16)
What is HIV?
HIV is a virus that affects the immune system and eventually causes AIDS
What is AIDS?
AIDS is a condition where the immune system deteriorates and eventually fails. People with AIDS are more vulnerable to infections and viruses.
How does HIV infect the body?
HIV infects and eventually kills helper T-cells, which act as host cells for the virus, reproducing it.
What has to occur for people with HIV to develop AIDS?
There has to be a dangerously low level of helper T-cells
Name the main components in the structure of HIV
Genetic material, reverse transcriptase, capsid, liquid membrane, attachment proteins, envelope.
What is the purpose of reverse transcriptase?
This enzyme is needed for virus replication.
Explain the life cycle of HIV
1)The HIV binds to protein receptors on helper T-cells
2) The capsid is released into the cell, where it uncoats and releases the genetic information into the helper T-cell's cytoplasm
3)Inside the cell, reverse transcriptase is used to make a complimentary strand of DNA from the viral RNA strand
4)Double stranded DNA is made and inserted into the cell's DNA
5)Host cell enzymes are used to make viral proteins from the DNA
6)The viral proteins are assembled into new viruses, which bud from the cell and infect other cells
What is the latency period?
After initial infection, when HIV develops rapidly and produces flu-like symptoms, replication drops to a lower layer, in which they wont experience any symptoms.
What are the initial symptoms of AIDS?
Initial symptoms include minor infections of mucous membranes and recurring respiratory infections
What happens as AIDS progresses?
The number of immune system cells decreases, so you become more susceptible to more serious infections.
What happens during the late stages of AIDS?
Patients have a very low number of immune system cells and develop several serious infections. It is these serious infections that kill people, not the HIV.
How do antibiotics kill bacteria?
By interfering with their metabolic reactions. They target bacterial enzymes and ribosomes.
Why don't antibiotics work against viruses?
Because antibiotics work by attacking a bacteria's growth machinery. Because a virus does not have any of this machinery, and are thousands of times smaller than bacteria, there is no target to attack.
Is there a cure for HIV?
Not currently, but antiviral drugs can be used to slow down progression.
Why is HIV so effective?
Because it attacks the helper T-cells, which play a vital role in the immune system and protecting the body from infection.
What is antigen variability?
It is the ability of certain pathogens such as viruses to alter the antigens on their outer surfaces. This prevents the pathogen from being easily recognised and destroyed by the immune system.
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