2C - Cells and the Immune System Flashcards Preview

A-Level Biology > 2C - Cells and the Immune System > Flashcards

Flashcards in 2C - Cells and the Immune System Deck (20)
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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