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Biology Paper 1 > Immunology > Flashcards

Immunology Flashcards

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1
Q

What is a pathogen?

A

a disease causing organism

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2
Q

Describe a virus.

A

acellular and non living
no nucleus, organelles, cytoplasm or cell membrane

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3
Q

What does a virus particle contain?

A
  • genetic material (RNA/DNA)
  • capsid
  • envelope
  • attachment protein
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4
Q

Where did viruses replicate?

A

in host cells

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5
Q

How are viruses replicated?

A
  • attach to host cell with complementary receptors
  • inject nucleic acid(RNA/DNA) into to host cell
  • genetic material codes for more virus particles
  • these are produced using organelles of the host cell
  • produce copies of nucleic acids and proteins to form complete viruses
  • viruses are released by lysis of the cell
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6
Q

What are non specific defence mechanisms?

A
  • the response is the immediate and the same for all pathogens

• physical barrier (skin)
• phagocytosis

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7
Q

Describe phagocytosis:

A
  • phagocyte engulfs pathogen
  • lysosome containing enzyme lysozyme fuses with phagosome and hydrolyse the pathogen

phagocyte can present antigen onto their cell surface membrane

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8
Q

What are specific defence mechanisms?

A

Response is slower and specific to each pathogen

  • t cells (cellular response)
  • b cells (humoral)
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9
Q

What is an antigen?

A

A protein/glycoprotein that may appear foreign to individual organisms exposed to them

• stimulate production if antibodies by b cells

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10
Q

Where may antigens be present?

A
  • surface if pathogen
  • cell surface membrane of other organisms of the same species
  • abnormal body cells (cancer)
  • as a toxin
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11
Q

Describe the Humoral response ( B cells)

A
  • b cells secrete antibodies into their surface
  • antigen complementary to antibody on b cell will bind
  • this stimulates b cell to divide by mitosis (clonal selection)
    -helpers t cells help them to divide
  • mitosis results in many plasma cells
  • plasma cells produce the same specific antibody and secrete it into blood plasma
  • some b cells divide into memory b cells
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12
Q

How do antibodies destroy antigens?

A

antibodies secreted by plasma cells bind to complementary antigen and form antigen-antibody complex

  • stimulates processes leading to antigen being destroyed
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13
Q

What is the primary response?

A

First response to new pathogen
- relatively slow and takes 72hrs to produce a significant concentration of antibody
- symptoms may occur during this time

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14
Q

How do memory B cells lead to the secondary response?

A

if the same antigen is encountered memory b cells will divide and develop into plasma cells

  • these plasma cells secrete antibodies more
    quickly and a higher concentration if them
  • provides immunity as pathogens are destroyed before symptoms develop
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15
Q

What is antigenic variation?

A

Some microorganisms have a high mutation rate
so even though you may be immune to one strain of the virus this wont provide immunity for any new forms

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16
Q

Where can antibodies be found?

A

breast milk
blood plasma
tissue fluid

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17
Q

Describe the structure if an antibody.

A

four polypeptide chains
2 heavy chains 2 light chains joined by disulphide bonds

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18
Q

what is the constant region of the antibody?

A

the sequence of amino acids is the same for every antibody

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19
Q

what is the variable region if the antibody?

A

sequence of amino acids vary between different molecules

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20
Q

Which processes destroy pathogens?

A

agglutination of antigens
stimulation of phagocytosis

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21
Q

What is agglutination?

A

clumping together cells containing the antigen specific to the antibodies

  • antibody uses its two binding sites to attatch to the same antigen present on two different cells
  • joins them together forming a massive clump of cells which is easily destroyed
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22
Q

How is phagocytosis stimulated?

A

an antibody attaches to the antigen on pathogen and identifies it for destruction by phagocytosis

  • phagocytes have receptors that recognise the antibody and enable them to bind to engulf the pathogen
23
Q

Describe the Cellular response ( t cells)

A
  • phagocyte presents antigen on its surface
  • t cell with complementary protein receptor will bing to antigen
  • stimulates t cells to divide by mitosis and form clones of identical t cells
24
Q

What do the clones t cells do?

A
  • activate cytotoxic t cells which attach to antigen and secrete chemicals to destroy it
  • develop into more helper t cells which stimulate b cells to divide
  • develop into memory t cells which remain in blood
25
Q

What is passive immunity?

A

Where individual receives pre formed antibodies from an outside source
- person not exposed to the antigens and don’t form antibodies of memory cells

  • short term immunity
26
Q

What is natural passive immunity?

A

antibodies are obtained across the placenta and through breast milk
this provides short-term immunity

27
Q

What is artificial passive immunity?

A

pre-formed antibodies are injected following exposure to infectious toxins/pathogen
short term protection

27
Q

What is active immunity?

A

individual is exposed to antigens and produces antibodies and memory cells
long term immunity

28
Q

What is natural active immunity?

A

results from the individual being infected and exposed to specific antigen
long term immunity

29
Q

What is artificial active immunity?

A

results from an individual being vaccinated and immune system produces its own antibodies

30
Q

What is in a vaccine?

A

vaccine contains antigens from a dead/weakened pathogen

31
Q

How does a vaccine work?

A

Injection stimulates primary immune response which produces plasma and memory b/t cells

32
Q

What is Herd immunity?

A

The higher the percentage of the population vaccinated against a pathogen the less risk of transmission

There is a low probability of an infected person encountering someone without immunity

33
Q

What is in HIV?

A
  • enzyme reverse transcriptase
  • RNA
  • attachment protein
  • capsid
  • viral envelope
34
Q

How can HIV be transmitted?

A
  • sex
  • blood transfusions
  • sharing needles
  • mother to baby (placenta)
35
Q

What is the function of the glycoprotein spikes?

A

They attach to complementary protein receptors on T cells

36
Q

How is RNA and reverse transcriptase released into the T cell

A

The lipid envelope fuses with the cell membrane of the host cell this releases RNA and RT

37
Q

What is the function of reverse transcriptase?

A

Uses RNA as a template to form viral DNA
- this viral DNA enters nucleus and attaches to host DNA
(can remain inactive for a long time)

38
Q

What is the function of the viral DNA?

A

controls the synthesis of viral RNA

39
Q

What is the function of viral RNA?

A

controls synthesis of viral proteins and more viral RNA

40
Q

How does HIV lead to AIDS?

A

They destroy T cells meaning the immune system no longer works and can’t fight off infections

41
Q

What is the first phases of the development of AIDS?

A

body produces HIV antibodies (may be flue-like illness)

42
Q

What is the second phases of the development of AIDS?

A

HIV positive phase
- the period between infection and the beginning of clinical signs

43
Q

What is the third phases of the development of AIDS?

A

AIDS-related complex
- results in a variety of microbial infections as number of T cells decrease

44
Q

What is the fourth phases of the development of AIDS?

A

Infections of body organs, possible cancers, weight loss, may die from pneumonia

45
Q

How do antibiotics work?

A

the affect cellular structures of bacteria such as, cell wall and ribosomes

46
Q

Why don’t antibiotics work for viruses?

A

Viruses don’t possess cellular structures

47
Q

What are monoclonal antibodies?

A

identical antibodies with the same antigen binding sites

48
Q

How do monoclonal antibodies target medication to specific cells?

A

a therapeutic drug is attached to an antibody

toxic cells have different antigens to healthy cells

monoclonal antibodies with a toxic drug attached can kill these cells without affecting healthy ones

49
Q

How are monoclonal antibodies used for medical diagnosis?

A

they can detect the presence of specific antigens of antibodies

50
Q

What is a direct ELISA test?

A

measures the concentration ANTIGENS and can determine if a pathogen is oresent

51
Q

What is an Indirect ELISA test?

A

measure’s concentration of ANTIBODIES and determine if someone has antibodies against a specific pathogen

52
Q

Describe a direct ELISA test

A
  • monoclonal antibody added to well
  • sample added and if specific antigen is present it will bind
  • second monoclonal antibody is added with enzyme attatched to it
  • well should be washed to remove any unbound second antibody
  • substrate for enzyme is added
  • if the enzyme is still present the colourless substrate turns into coloured product
53
Q

Describe an indirect ELISA test?

A

its the same as a direct ELISA but in an antigen is added to the well

Biology Paper 1 (8 decks)

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