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Biology A Level > Immunity > Flashcards

Immunity Flashcards

1
Q

What are antigens?

A

Molecules on the surface of cells that generate an immune response by detecting pathogens, abnormal body cells, toxins and foreign cells.

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2
Q

What is a phagocyte?

A

Type of white blood cell that is found in the blood and tissues - they’re the first cells to create an immune response.

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3
Q

Describe phagocytosis.

A
  • Phagocyte identifies foreign antigens on pathogen, it’s cytoplasm modes around the pathogen engulfing it
  • The pathogen become consigns in the phagocytic vacuole
  • Lysosome fuses with phagocytic vacuole and the lysozymes break down the pathogen
  • The phagocyte then presents the pathogens antigens, putting them on the surface of immune system cells
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4
Q

What happens after phagocytosis?

A

Phagocytes activate T-cells.

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5
Q

What is a T-cell?

A

White blood cell with receptor proteins on surface that bind to complement astray antigens presented by phagocytes, activating them.

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6
Q

How do helper T-cells and cytotoxic T-cells act differently?

A

Helper T-cells release chemical signals that activate phagocytes,cytotoxic T-cells and B-cells which secrete antibodies.
Cytotoxic T-cells kill abnormal and foreign cells.

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7
Q

What are B-cells?

A

White blood cells that are covered in antibodies - bind to antigens to from antigen-antibody complex. Each has a side rent shaped antibody.

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8
Q

How do B-cells work?

A

When antibody meet a complementary antigen they bind creating antigen-antibody complex. This along with the chemicals from the helper T-cells activates the B-cells and divides into plasma cells in clonal selection.

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9
Q

Describe plasma cells.

A

They are clones of B-cells that secret monoclonal antibodies specific to antigens, form antigen-antibodies complexes.

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10
Q

Describe how plasma cells work.

A

Antibodies secreted by plasma cells have two binding sites so can bind to two pathogens at one end causing them to agglutinate (clump)m making it easy for phagocytes to bind and under go phagocytosis of multiple pathogens - destroy for them.

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11
Q

What are antibodies?

A

Proteins with a variable region which forms the antigen biding site. Has a unique tertiary structure that is complementary to a specific antigen. All have same constant region.

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12
Q

What are the two types of immune response?

A

Cellular - helper T-cells, cytotoxic T-cells, phagocytes

Humoral - B-cells, plasma cells

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13
Q

What is the primary immune response?

A

When antigen enters body for first time it activates immune system, slow as aren’t many B-cells that make the correct antibody.

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14
Q

What happens when the body produces enough B-cells in the primary response?

A

Person shows symptoms, after being exposed to antigen T and B cells produce memory cells that remembers the antigen and the antibody that’s needed - person is immune.

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15
Q

Describe the secondary immune response.

A

Quicker stronger immune response, clonal selection happens faster - B-cells activated producing plasma cells which produce the correct antibody, memory T-cells activated and create correct type of T-cell to kill the antigen.

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16
Q

How do vaccines work?

A

Cause body to produce memory cells against pathogen without catching disease, immune without any symptoms.

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17
Q

What is herd immunity?

A

Rescued occurrence of disease as people immune so people without immunity as less likely to catch the disease.

18
Q

How are vaccinations carried out?

A

Dead attenuated version of pathogen injected or taken orally allowing memory cells to be produced.

19
Q

Disadvantage of oral vaccine.

A

Molecules may be to large to be absorbed into the blood or broken down by enzymes.

20
Q

What is antigenic variation?

A

Some antigens can change their surface antigens as a result of gene mutation.

21
Q

What issues does antigenic variation create?

A

Difficult to develop some vaccines due to antigenetic variation.

22
Q

Describe the influenza vaccine.

A

New vaccine very year as antigens on virus change regularly forming new strains, memory cells from one strain will not work with another as they are immunologically distinct. New vaccines have to be created each year and the most effective is selected.

23
Q

Describe active immunity.

A

Immune system makes own antibodies after being stimulated by an antigen:

  • natural after catching disease
  • artificial after being given a vaccination
24
Q

Describe passive immunity.

A

Immunity when given antibodies made by a different organism, no antibodies are produced yourself:

  • natural when baby receives antibodies from mother through placenta and breast milk
  • artificial when immune after being injected with someone else’s antibodies
25
Q

Primary differences between active and passive immunity.

A
  • active, requires exposure to antigen, passive doesn’t
  • active, takes while to develop protection, passive immediate
  • active, memory cells are produce, passive aren’t
  • active, protection is long term as antibody produced with Monroe cells, passive isn’t as antibodies eventually brown down
26
Q

What is a monoclonal antibody?

A

Produced from single group of genetically identical (in structure) B cells and can be made to bind to any specific molecule.

27
Q

What is a positive of monoclonal antibodies?

A

Reduced side affects compared to non-antibody drug as they only attack specific cells.

28
Q

What does the ELISA so and what is it used for?

A

Tests to see if patient has certain antibodies or antigens. Can test for pathogenic infections for allergies or anything needed for antibodies.

29
Q

How does the ELISA test work?

A
  1. Antibody with attached enzyme that can react with coloured precipitate to produce coloured product causing solution to change colour.
  2. Colour change demonstrates antigen or antibody of interest is present - with intensity of colour indicating amount.
30
Q

Describe the two different types of ELISA.

A
  • direct ELISA uses single complementary antibody

- indirect ELISA uses two different antibodies

31
Q

Describe indirect ELISA as a HIV test.

A
  1. HIV antigen bound to bottom of well in well plate
  2. Sample of blood plasma (contains antibodies) is added and any HIV specific antibodies bind to antigen, any unbound washed out
  3. Secondary antibody with enzyme added which can bind to the primary antibody, if no primary antibodies all the secondary will be washed away
  4. Solution containing a substrate added which reacts to enzyme producing a coloured product - if solution changes colour it indicates HIV specific antibodies meaning the blood is infected with HIV
32
Q

What are the ethical issues surrounding vaccines?

A
  • tested on animals which some people disagree with
  • testing vaccines on humans is difficult due to unnecessary risk
  • some people think taking vaccine due to risk of side effects but still protected from herd immunity which some think is unfair
  • who should receive a vaccine first
33
Q

Ethical issues surrounding monoclonal antibodies.

A

Animals often used to produce cells from which monoclonal antibodies are produced.

34
Q

What does HIV do?

A

Infects and kills helper T cells which act as host cells for the virus, without them chemical signal can’t be sent to activate phagocytes, cytotoxic T cells and B cells, preventing effective immune response to infections - develops into AIDS when help T cell numbers are critically low.

35
Q

What are the elements of HIV structure?

A

Core, capsid, envelope, attachment proteins.

36
Q

What do the capsid, core, envelope and attachment proteins do?

A

Core - contains genetic material and proteins (including reverse transcriptase needed for replication)
Capsid - protein outer coating to core
Envelope - outer layer made from membrane of previous hose cells
Attachment proteins - allow HIV to attach to host helper T cells

37
Q

Describe how HIV replicates.

A
  • Attachment protein attaches to receptor molecule on host helper T cells
  • Capsid released into cell where it uncoats and releases genetic material
  • Reverse transcriptase used to make complementary strand of DNA from viral RNA template from which DNA is made and inserted into human DNA
  • Host cells enzymes used to make viral proteins from viral DNA in human DNA which are assembled into new viruses
38
Q

What is the latency period of HIV?

A

When replication drops to a lower level and the infected experiences no symptoms.

39
Q

What don’t antibiotics work against viruses?

A

Antibiotics kill bacteria by targeting enzymes and ribosomes used in metabolic reactions, viruses don’t have their own enzymes and ribosomes (use host cells) so antibiotics wouldn’t work as they don’t target human processes and would affect host cell.

40
Q

What are reverse transcriptase inhibitors?

A

Antiviral drug that targets reverse transcriptase preventing HIV from replicating without affecting the host cell as only HIV uses this enzyme.

Biology A Level (14 decks)

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