2C - Cells and the Immune System Flashcards
1
Q
What are the the four main stages of the immune response?
A
- phagocytes engulf pathogens
- phagocytes activate T-cells
- T-cells activate B-cells, divide into plasma cells
- plasma cells make more antibodies to specific antigen
2
Q
How does a phagocyte engulf a pathogen?
A
- foreign antigens are recognised
- cytoplasm moves round the pathogen
- pathogen is now contained in a phagocytic vacuole
- lysosome fuses with the vacuole, breaks down pathogen
- antigens are presented by sticking to phagocytes’ surface to activate other immune system cells
3
Q
How do phagocytes activate T-cells?
A
- it’s receptor proteins bind to complementary antigens presented to it
- helper T-cells release chemical signals
- cytotoxic T-cells kill abnormal and foreign cells
4
Q
How do T-cells activate B-cells?
A
- antibodies on a B-cell binds to a complementary shaped antigen
- clonal selection
- B-cell divides into plasma cells
5
Q
What is the primary immune response?
A
- antigen enters the body for this 1st time
- slow response
- memory cells are produced
6
Q
What is the secondary immune response?
A
- same pathogen enters the body again
- quicker, stronger response
- clonal selection is faster
7
Q
What are vaccines?
A
- contain dead or inactive antigens that cause the body to produce memory cells
8
Q
What is meant by ‘antigenic variation’?
A
- pathogens change their surface antigens
- memory cells will not recognise the different antigens
- immune system has to have primary immune response
9
Q
What is meant by ‘active immunity’?
A
- immune system makes its own antibodies after being stimulated
- natural (becoming immune after catching the disease)
- artificial (vaccinations)
10
Q
What is meant by ‘passive immunity’?
A
- immune system doesn’t produce any antibodies on its own
- natural (baby becomes immune due to antibodies from its mother)
- artificial (injected antibodies from someone else)
11
Q
What are the differences between active and passive immunity?
A
- active requires exposure to antigens, passive doesn’t
- passive had immediate protection, active takes a while
- active produces memory cells, passive doesn’t.
- passive is short term, active is long term
12
Q
What are ‘monoclonal antibodies’?
A
- produced from a single group of genetically identical B-cells
- used to target specific substances or cells
13
Q
What are the stages in an ELISA test?
A
- antibody with an enzyme attached is used.
- enzyme reacts with a substrate to produce a coloured product
- colour change means antigen or antibody is present
14
Q
What are the ethical issues surrounding vaccines?
A
- tested on animals before humans
- animal based substances are used
- tricky, risky
- people don’t want to do it due to side effects, but still protected because of herd immunity
- new epidemic means increased demand for vaccinations
15
Q
What is the ethical issue surrounding monoclonal antibody therapy?
A
- animals are used to produce cells so monoclonal antibodies can be produced
16
Q
What is HIV / AIDS?
A
- virus that affects the immune system
- immune system deteriorates and eventually fails
- people become more susceptible to infections
- kill helper T-cells
17
Q
What is the structure of HIV?
A
- a core that contains RNA and proteins
- outer coating of protein (capsid)
- extra outer layer (envelope) made of membrane
- many copies of attachment proteins sticking out
18
Q
How does HIV replicate inside a helper T-cell?
A
- attachment protein attaches to receptor molecule on cell membrane of T-cell
- capsid is released, uncoats and releases RNA into cells cytoplasm
- reverse transcriptase makes complementary strand of DNA from viral RNA template
- double stranded DNA is made and inserted into DNA
- host cell enzymes make viral proteins from viral DNA
- viral proteins are assembled into new viruses which leave the cell and infect other cells
19
Q
What are the symptoms of AIDS?
A
- initial symptoms include minor infections of mucous membranes and respiratory infections.
- no. of immune system cells decrease
- late stages mean very low number of immune system cells and serious infections of the brain and respiratory system occur
20
Q
Why can’t antibiotics work against viruses?
A
- antibiotics do not target human processes
- they attack bacterial enzymes and ribosomes
- viruses don’t have enzymes or ribosomes, they use the host cells
- antibiotics can’t inhibit them
