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AQA A-level Bio + Chem + P.E. > Immunity > Flashcards

Immunity Flashcards

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1
Q

What is an antigen?

A

A cell-surface molecule which stimulates an immune response

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2
Q

How does phagocytosis destroy pathogens?

A
  1. Phagocyte moves towards pathogen via chemotaxis
  2. Phagocyte engulfs pathogen to form a phagosome (endocytosis)
  3. Phagosome fuses with lysosome
  4. Lysozymes digest pathogen
  5. Phagocyte absorbs product from pathogen’s hydrolysis
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3
Q

What is the role of the antigen-presenting cells?

A

Enhances recognition by T helper cells

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4
Q

What’s the difference between specific and non-specific immune responses?

A

Non-specific = same for all pathogens + immediate
e.g. phagocytosis
Specific = requires complementary pathogen + has a time lag
e.g. cell-mediated + humoral response

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5
Q

Outline the process of the cell-mediated response

A
  1. Complementary T lymphocytes bind to foreign antigen
  2. Release cytokines that stimulate the clonal expansion of complementary T helper cells (become memory cells or trigger humoral response)
    or
    cytotoxic T cells that secrete the enzyme perforin to destroy infected cells
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6
Q

Outline the process of the humoral response

A
  1. Complementary T 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
  4. Plasma cells secrete antibodies with complementary variable region to antigen
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7
Q

What is an antibody?

A

A protein secreted by plasma cells

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8
Q

Describe the structure of an antibody

A

2 light chains and 2 heavy chains held together by disulfide bridges
Binding sites on variable region are complementary to antigen

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9
Q

What are monoclonal antibodies?

A

Antibodies produced from a single clone of B cells

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10
Q

How do the primary and secondary immune response differ?

A

SECONDARY
faster rate of antibody production
no time delay between exposure and antibody production
higher concn of antibodies

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11
Q

Compare and contrast active and passive immunity

A

Both involve antibodies
Passive natural = antibodies in breast milk
Passive artificial = anti-venom
Active natural = humoral response
Active artificial = vaccination
PASSIVE
no memory cells produced when broken down (short-term)
immediate
ACTIVE
memory cells produced (long-term)

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12
Q

How does a vaccine work?

A
  1. Vaccine contains inactive form of a pathogen
  2. Triggers primary immune response
  3. Memory cells produced / remain in bloodstream
  4. Secondary response more rapid as higher concn antibodies destroys pathogen before any symptoms occur
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13
Q

What is herd immunity?

A

Vaccinating a large proportion of the population reduces the available carriers of the pathogen

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14
Q

What may be some ethical issues with the use of vaccines and monoclonal antibodies?

A

May involve the use of animals
Potentially dangerous side effects
Clinical tests may be fatal

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15
Q

Describe the structure of HIV

A

Genetic material + reverse transcriptase surrounded by a capsid
Surrounded by viral envelope from host cell
Attachment proteins on surface

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16
Q

How does HIV result in the symptom of AIDS?

A
  1. Attachment proteins bind to receptor on T helper cells
  2. HIV particles replicate inside T helper cells which kills them
  3. Too few T helper cells allows AIDS to develop as the immune system cannot function
  4. Individuals cannot destroy other’s pathogens (suffer from secondary disease)
17
Q

Why are antibiotic ineffective against viruses?

A

Antibiotics work by damaging the cell wall
Viruses don’t have a cell wall
They replicate inside the host cell

18
Q

Outline the process of a direct ELISA test

A
  1. Monoclonal antibodies bind to bottom of test plate
  2. Antigens bind to antibodies, rinse excess
  3. Antibody with enzyme attached binds to antigen, rinse excess
  4. Add substrate for enzyme with a +ve result changing colour
19
Q

Outline the process of an indirect ELISA test

A
  1. Antigens bind to bottom of test plate
  2. Antibodies bind to antigens, rinse excess
  3. Secondary antibody with enzyme attached binds to primary antibody
  4. Add substrate for enzyme with a +ve result changing colour

AQA A-level Bio + Chem + P.E. (95 decks)

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