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biology > 5 cell recognition and immune system > Flashcards

5 cell recognition and immune system Flashcards

1
Q

state 2 ways pathogens can cause harm

A

pathogens can produce toxins that damage tissue
pathogens can replicate inside and destroy host cells

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2
Q

what can the molecules on the plasma cell surface membrane identify?

A

pathogens
abnormal body cells
toxins
cells from other organisms of the same species

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3
Q

what is an antigen?

A

an antigen is a molecule that stimulates an immune response that results in the production of a specific antibody

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4
Q

what happens if antigens on a cell are not recognised?

A

the body will treat the cell as non self and initiate an immune response. this will destruct the cell

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5
Q

what are phagocytes?

A

groups of white blood cell

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6
Q

what does a phagocyte do?

A
  1. pathogen engulfed by phagocyte
  2. pathogen enters the cytoplasm of the phagocyte in a vesicle which is now called a phagosome
  3. lysosomes fuse with phagosome releasing lysozymes
  4. lysozymes hydrolyse pathogen
  5. waste materials are released by exocytosis and antigens are presented on the membrane making the pathogen an APC
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7
Q

what type of process is phagocytosis?

A

non specific.

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8
Q

what does non specific mean?

A

works the same for any cell that displays a non self antigen

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9
Q

why does phagocytosis not work all the time?

A

non specific so would take too long to destroy all pathogens in an infection resulting in damage to tissues and organs

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10
Q

what is a specific response?

A

specific to certain antigens or pathogens that have been recognised as non self

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11
Q

what are the 2 types of specific immunity?

A

cell mediated
humoural

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12
Q

what are the 3 stages of the cell mediated response?

A
  1. antigen presenting
  2. clonal selection
  3. role of t cells
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13
Q

describe antigen presenting stage of cellular response.

A

TH cells respond directly to specific pathogen or respond to APC (from phagocytosis) that presents specifically complementary antigen

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14
Q

explain clonal selection as a part of the cellular response

A
  1. specific TH cell binds to presented antigen via its complementary receptor
  2. TH cell activated and clones by mitosis (produces cells with complementary receptors to the antigen)
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15
Q

what is the role of a TH cell?

A
  1. binds to antigen on presenting cell
  2. releases cytokines that attract phagocytes and activate Tc cell
  3. activates specifically complementary B cell
  4. form memory Th cells
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16
Q

what is a Tc cell?

A

cytotoxic killer cell

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17
Q

what is the role of a Tc cell?

A
  1. locate and destroy infected body cell
  2. binds to APC
  3. releases perforin which created holes in the cell surface membrane
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18
Q

how are B cells activated in the humoral response?

A
  1. specific TH cell binds to APC and locates and activates a specifically complementary B cell
  2. TH cell releases cytokine that signals the B cell to clone by mitosis
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19
Q

what happens when the B cell clones by mitosis?

A

B cell differentiates into
plasma cell or memory B cell

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20
Q

what do plasma cells do?

A

produce and secrete vast quantities of specific antibodies into blood plasma

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21
Q

what do memory B cells do?

A

remain in body to respond to pathogen rapidly in case of future infection

22
Q

what is an antibody?

A

a protein made in response to a foreign antigen

23
Q

what is a specific antibody produced by?

A

specific plasma cell

24
Q

describe the antibody structure

A
  • complex protein with 4° structure
  • 4 polypeptide chains
  • Y shaped
  • constant region
  • variable region
  • antigen binding site
  • peptide bonds and disulphide bridges
25
Q

what is the constant region of an antibody?

A

the main part which is the same in all antibodies

26
Q

what is the variable region in an antibody?

A

have a different 1° and 3° structure
binding site specific which is different for each antibody

27
Q

antibodies have specific binding sites. what does this lead to?

A

they can only bind to specific antigens forming an antibody antigen complex

28
Q

how do antibodies assist destructing pathogens?

A
  1. agglutination
  2. opsonisation
  3. lysis
  4. anti toxin and anti venom
  5. prevent pathogen replication
29
Q

what does agglutination mean referring to antibodies?

A

specific antibodies bind to antigen on pathogen and clump them together

30
Q

what does opsonisation mean referring to antibodies?

A

mark pathogens so phagocytes recognise and destroy pathogen efficiently

31
Q

what does lysis mean referring to antibodies?

A

bind to antigen and lead to destruction of pathogens membrane

32
Q

what does anti toxin and anti venom mean referring to antibodies?

A

binds to toxins or venom to prevent these molecules from binding to complementary target receptors

33
Q

what happens if B memory cells encounter the antigen again?

A
  1. they are rapidly activated by cytokines (TH cell) and divide rapidly by mitosis
  2. clone into plasma cells and more memory cells
  3. plasma cells produce lots of specific antibodies for the pathogen QUICKLY
34
Q

what is the secondary response?

A

the activation of memory cells to produce antibodies

35
Q

why don’t some illnesses like HIV initiate a secondary response?

A

antigens mutate and change shape so pathogen will not be recognised and secondary response can’t be initiated. (antigenic variability)

36
Q

which two ways can immunity be gained?

A

active
passive

37
Q

what is passive immunity?

A

antigens aren’t produced by individual so no production of memory cells

38
Q

what is active immunity?

A

antibodies produced in exposure to antigen so memory cells are produced

39
Q

give an example of passive immunity

A

vaccine

40
Q

how do vaccines work?

A
  1. vaccines contain antigens from dead weakened or attenuated pathogens
  2. body carries out non specific and specific immunity
41
Q

what are vaccines not effective against?

A

pathogens that show antigenic variability

42
Q

define herd immunity

A

if enough individuals in the population are vaccinated (85%), there is little chance of the disease spreading and even non vaccinated individuals will be protected

43
Q

give 6 ethical issues associated with vaccines

A
  1. animal testing
  2. human testing
  3. availability to all countries
  4. side effect risks
  5. should they be compulsory?
  6. should we be aiming to eliminate an organism?
44
Q

explain the elisa test

A
  1. monoclonal antibodies fixed to surface of test well
  2. sample containing X binds to complementary antibody
  3. more monoclonal antibody and enzyme attached added and binds to X
  4. washed so any unbound antibodies removed
  5. substrate added- colour change
45
Q

describe the structure of HIV

A
  • HIV envelope
  • HIV capsid
  • HIV enzymes
  • HIV RNA
  • attachment protein
46
Q

what is the role of the capsid in HIV?

A

contains HIV RNA

47
Q

how does HIV replicate?

A
  1. attachment protein binds to protein on TH cells
  2. capsid fuses with membrane and releases viral RNA and enzymes into T cell
  3. HIV’s reverse transcriptase converts RNA into cDNA
  4. viral cDNA enters nucleus of T cell and inserted into the DNA
  5. transcription leads to translation of HIV proteins
  6. reduces number of TH cells
48
Q

how does HIV lead to symptoms of AIDS?

A

HIV reduces the ability to respond to pathogens as their cell mediated immunity is compromised so they have less TH cells
symptoms: infections, weight loss, diarrhoea

49
Q

how do antibiotics work?

A

prevent bacteria from making a normal cell wall by targeting 70s ribosomes
bacteria unable to resist osmotic pressure so burst

50
Q

why don’t antibiotics act on viruses?

A

viruses don’t have a cell wall (capsid instead)

biology (23 decks)

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