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Biology Year 12 > Cell recognition & the immune system (5) > Flashcards

Cell recognition & the immune system (5) Flashcards

1
Q

What is an antigen?

A

cell-surface molecule which stimulates immune response

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2
Q

What are antigens usually?

A

glycoproteins, sometimes glycolipids or polysaccharides

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3
Q

What is the advantage of the immune system recognising ‘self’ and ‘non-self’?

A

enables identification of cells from other organisms of same species, pathogens, toxins and abnormal body cells

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4
Q

How can organisms identify cells, pathogens, toxins and abnormal cells?

A

immune system recognises ‘self’ and non-self’

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5
Q

What are the 5 steps on how phagocytosis destroys pathogens?

A

1) phagocyte moves towards pathogen via chemotaxis
2) phagocyte engulfs pathogen via endocytosis to form a phagosome
3) phagosome fuses with lysosome (phagolysosome)
4) lysozymes digest pathogen
5) phagocyte absorbs products from pathogen hydrolysis

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6
Q

What are the 2 roles of antigen-presenting cells?

A
  • macrophage displays antigen from pathogen on its surface after hydrolysis in phagocytosis
  • enhances recognition by T helper cells, which cannot directly interact with pathogens/antigens in body fluid
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7
Q

What are the 2 types of immune response?

A

nonspecific
specific

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8
Q

What does the non-specifc response involve?

A

inflammation
phagocytosis

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9
Q

What does the specific response involve?

A

B and T lymphocytes

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10
Q

What are 2 differences between the non-specific and specific responses?

A
  • non is same for all pathogens, specific is complementary to pathogen
  • non is immediate, specific has a time lag
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11
Q

What are the 2 types of specific response?

A

cell-mediated
humoral

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12
Q

What are the cell-mediated and humoral responses?

A

types of specific immune responses

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13
Q

What are the 2 steps of the cell-mediated response?

A

1) complementary T helper lymphocytes bind to foreign antigen on antigen-presenting cells
2) release cytokines that stimulate 2 things

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14
Q

What 2 things do cytokines stimulate in the cell-mediated response?

A
  • clonal expansion of complementary T helper cells (rapid mitosis) so they become memory cells or trigger the humoral response
  • clonal expansion of cytotoxic T cells which secretes the enzyme perforin to destroy infected cells
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15
Q

What are the 3 steps of the humoral response?

A

1) complementary T helper lymphocytes bind to foreign antigen on antigen-presenting T cells
2) release cytokines that stimulate clonal expansion of complementary B lymphocytes
3) B cells differentiate into plasma cells which secrete antibodies with complementary variable region to antigen

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16
Q

What are antibodies?

A

proteins secreted by plasma cells

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17
Q

How does the quaternary structure relate to antigens?

A

The quaternary structure has 2 light chains which have binding sites on variable regions that have a specific tertiary structure complementary to an antigen. The rest of the molecule is known as the constant region.

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18
Q

How do antibodies lead to the destruction of a pathogen?

A

form antigen-antibody complex which results in agglutination, which enhances phagocytosis

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19
Q

What are monoclonal antibodies?

A

antibodies produced from a single clone of B cells

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20
Q

What are memory cells?

A

specialised T helper and B cells produced from the primary immune response

21
Q

Where are memory cells found?

A

remain in low levels in the blood

22
Q

What is the function of memory cells?

A

can divide rapidly by mitosis if organism encounters the same pathogen again

23
Q

What are 5 differences between the primary and secondary responses?

A

Secondary response:
- faster rate of antibody production
- shorter time lag between exposure and antibody production
- high concentration of antibodies
- antibody level remains high after secondary response
- pathogen usually destroyed before any symptoms

24
Q

What 4 factors cause antigen variability?

A

1) random genetic mutation changes DNA base sequence
2) results in different sequence of codons on mRNA
3) different primary structure of antigen means H-bonds, ionic bonds and disulfide bridges form in different places in tertiary structure
4) different shape of antigen

25
Q

What 2 ways does antigen variability affect incidence of disease?

A
  • memory cells no longer complementary to antigen so individual is not immune so can catch the disease more than once
  • many varieties of a pathogen so difficult to develop vaccine containing all antigen types
26
Q

What are 2 similarities between passive and active immunity?

A
  • both involve antibodies
  • both can be natural or artificial
27
Q

What are the 4 types of immunity?

A

passive natural
passive artificial
active natural
active artificial

28
Q

What is an example of passive natural immunity?

A

breast milk

29
Q

What is an example of passive artificial immunity?

A

anti-venom

30
Q

What is an example of active natural immunity?

A

humoral response to infection

31
Q

What is an example of active artificial immunity?

A

vaccination

32
Q

What are 5 features of passive immunity?

A
  • no memory cells as it is a short-term response
  • antibodies not replaced when broken down as it is a short-term response
  • immediate
  • antibodies from external source
  • direct contact with antigen not necessary
33
Q

What are 4 features of active immunity?

A
  • memory cells produced as it is a long-term response
  • time lag
  • lymphocytes produced antibodies
  • direct contact with antigen necessary
34
Q

What are vaccinations made from?

A

contains dead/inactive form of pathogen or antigen

35
Q

What 3 things do vaccinations do?

A

1) trigger primary immune response
2) cause memory cells to be produced and remain in bloodstream so secondary response is rapid and produces higher concentration of antibodies
3) ensures pathogen is destroyed before it causes symptoms

36
Q

What is herd immunity?

A

when large proportion of population is vaccinated to reduce the available carriers of the pathogen

37
Q

What is the benefit of herd immunity?

A

protects individuals who have not been vaccinated e.g. those with a weak immune system

38
Q

What are 3 ethical issues of vaccinations?

A
  • production may involve use of animals
  • potentially dangerous side-effects
  • clinical tests may be fatal
39
Q

What is the structure of HIV?

A
  • genetic material (x2 RNA) and viral enzymes (integrase and reverse transcriptase) surrounded by capsid
  • surrounded by viral envelope derived from host cell membrane
  • GP120 attachment proteins on surface
40
Q

What are 2 reasons why antibiotics are ineffective against viruses?

A

1) antibiotics often work by damaging murein cell walls to cause osmotic lysis, however viruses have no cell wall
2) viruses replicate inside host cells so it is difficult to destroy them without damaging normal body cells

41
Q

What are the 4 steps in how HIV results in symptoms of AIDS?

A

1) attachment proteins bind to complementary CD4 receptor in T helper cells
2) HIV particles replicate inside T helper cells, killing or damaging them
3) AIDS develops when there are too few T helper cells for immune system to function
4) individuals cannot destroy other pathogens and suffer from secondary diseases/infections

42
Q

What are 3 clinical applications of monoclonal antibodies?

A

1) pregnancy tests by detecting HCG hormones in urine
2) diagnostic procedures e.g. ELISA test
3) targeted treatment by attaching drug to antibody so it only binds to cells with abnormal antigen e.g. cancer cells due to specificity of tertiary structure of binding site

43
Q

What does the direct ELISA test do?

A

detects presence of a specific antigen

44
Q

What are the 4 steps of a direct ELISA test?

A

1) monoclonal antibodies bind to bottom of test plate
2) antigen molecules in sample bind to antibody (rinse excess)
3) mobile antibody with reporter enzymes attached, binds to antigens that are fixed on the monoclonal antibodies (rinse excess)
4) add substrate for reporter enzyme, a positive result will cause a colour change

45
Q

What are the 2 types of ELISA test?

A

direct
indirect

46
Q

What does the indirect ELISA test do?

A

detects presence of antibody against specific antigen

47
Q

What are the 4 steps of the indirect ELISA test?

A

1) antigens bind to bottom of test plate
2) antibodies in sample bind to antigen (rinse excess)
3) secondary antibody with receptor enzyme attacked, binds to primary antibodies from the sample
4) add substrate for reporter enzyme, a positive result will cause a colour change

48
Q

What are 2 ethical issues of monoclonal antibodies?

A
  • production involves animals
  • drug trials against arthritis and leukaemia resulted in multiple organ failures

Biology Year 12 (22 decks)

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