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A-LEVEL AQA- BIOLOGY > 3.2.4 Cell recognition and the immune system > Flashcards

3.2.4 Cell recognition and the immune system Flashcards

1
Q

Non-specific - Phagocytosis (3),

A
  1. Phagosome/vesicle fuses with lysosome;
  2. (pathogen) destroyed by lysozymes/hydrolytic enzymes;
  3. Antigen (from pathogen) displayed on cell membrane (of phagocyte/antigen presenting c
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2
Q

Describe how a phagocyte
destroys a pathogen present in the
blood.(3)

A
  1. Engulfs;
    Accept endocytosis
    OR
    Description
    Ignore ‘taken in’
  2. Forming vesicle/phagosome and fuses with lysosome;
  3. Enzymes digest/hydrolyse;
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3
Q

Describe how presentation of
a virus antigen leads to the secretion of
an antibody against this virus antigen.

A
  1. Helper T cell / TH cell binds to the antigen (on the antigen-presenting cell / phagocyte);
  2. This helper T / TH cell stimulates a specific B cell;
  3. B cell clones
    OR
    B cell divides by mitosis;
  4. (Forms) plasma cells that release antibodies;
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4
Q

What is antigen? (2

A
  1. Foreign protein;
  2. (that) stimulates an immune response/production of antibody
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5
Q

What is antibody? (2)

A
  1. A protein/immunoglobulin specific to an antigen;
  2. Produced by B cells OR Secreted by plasma cells;
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6
Q

Explain Antibody specificity (4)

A
  1. Antibody has (specific) tertiary structure
  2. Has binding site/ variable region which only binds to one antigen
  3. Antigen is only found on this particular (pathogen/cell/tissue)
  4. so antibody (only) binds to / forms antigen/antibody complex with these (pathogen/cell/tissue) destroying them
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7
Q

Explain Antigen-Antibody
complex formation (4)

A
  1. Antibody has 4 polypeptide chains and has a quaternary structure
  2. Antibody has a variable region which has a specific amino acid sequence/primary structure
  3. Shape of the binding site is complementary to the antigen
  4. Forming an antigen-antibody complex
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8
Q

Explain the Humoral Response (6)

A
  1. Antigen on surface of bacterium binds to surface protein / surface receptor on a (specific/single) B cell;
  2. (Activated) B cell divides by mitosis / produces clone;
  3. (Division) stimulated by cytokines / by T cells;
  4. B cells/plasma cells release antibodies;
  5. (Some) B cells become memory cells;
  6. Memory cells produce plasma / antibodies faster;
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9
Q

Give two types of cell, other
than pathogens, that can stimulate an
immune response.(2)

A
  1. (Cells from) other organisms/transplants;
  2. Abnormal/cancer/tumour (cells);
  3. (Cells) infected by virus;
  4. Antigen presenting cells
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10
Q

Draw a labelled diagram of an
antibody (3)

A
  1. Y shape showing two long and two short (polypeptide) chains correctly positioned;
  2. binding site labelled on the end of the branches of the Y of the antibody;
    Accept one or two being labelled, if two both must be correct.
  3. Variable region labelled /Constant region labelled / Disulfide bridge/bond labelled;
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11
Q

Describe and explain the role
of antibodies in stimulating
phagocytosis.
Do not include details about the
process of phagocytosis.

A
  1. Bind to antigen
    OR
    Are markers;
    Accept opsonin for ‘marker’
    Accept form (antibody-antigen) complexes/are complementary to antigen
  2. (Antibodies) cause clumping/agglutination
    OR
    Attract phagocytes;
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12
Q

Compare Active and
Passive Immunity (6)

A
  1. Active involves memory cells, passive does not;
  2. Active involves production of antibody by plasma cells/memory cells;
  3. Passive involves antibody introduced into body from outside/named source;
  4. Active long term, because antibody produced in response to antigen;
  5. Passive short term, because antibody (given) is broken down;
  6. Active (can) take time to develop/work, passive fast acting;
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13
Q

Compare Primary
and
Secondary Response (4)

A
  1. Before vaccination no antibody released because patients not yet encountered vaccine/antigen/virus;
  2. Primary response/after first dose) activation/clonal selection/expansion of B cells into plasma cells;
  3. Plasma cells release antibodies;
  4. Secondary response/after second dose) memory cells produce more antibodies/produce antibodies more
    quickly;
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14
Q

How does a vaccine produces an immune response (7)

A
  1. Vaccine contains antigen from pathogen;
  2. Macrophage presents antigen on its surface;
  3. T cell with complementary receptor protein binds to antigen;
  4. T cell stimulates B cell;
  5. (With) complementary antibody on its surface;
  6. B cell/plasma cell secretes large amounts of antibody;
  7. B cell divides to form clone all secreting/producing same antibody;
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15
Q

Explain why giving children
more than one vaccination develops
good immunity (2)

A
  1. (Production of more) memory cells;
  2. (So) higher concentration of (circulating) antibodies in blood
    OR
    (So) rapid production of antibodies (on further infection)
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16
Q

Determining the genome of
the viruses could allow scientists to
develop a vaccine.
Explain how.(2)

A
  1. (The scientists) could identify proteins (that derive from the genetic code)
    OR
    (The scientists) could identify the proteome;
  2. (They) could (then) identify potential antigens (to use in the vaccine);
17
Q

Describe how B lymphocytes
would respond to vaccination

A
  1. B cell (antibody) binds to (viral) specific/complementary receptor/antigen;
    Accept B cell forms antigen-antibody complex
  2. B cell clones
    OR
    B cell divides by mitosis;
  3. Plasma cells release/produce (monoclonal) antibodies (against the virus);
  4. (B/plasma cells produce/develop) memory cells;
18
Q

Describe and explain HIV treatment with anti-retroviral
drug AZT (6)

A
  1. Person (infected with HIV) has HIV DNA (in their DNA);
  2. New HIV (particles) still made;
  3. (AZT) inhibits reverse transcriptase;
  4. (AZT) stops replication of HIV;
  5. Stops destruction of more / newly infected T cells;
  6. So immune system continues to work (and AIDS does not develop);
19
Q

Describe how HIV is replicated (5)

A
  1. Attachment proteins attach to receptors on helper T cell/lymphocyte;
  2. Nucleic acid/RNA enters cell;
  3. Reverse transcriptase converts RNA to DNA;
  4. Viral protein/capsid/enzymes produced;
  5. Virus (particles) assembled and released (from cell);
20
Q

Describe how the human
immunodeficiency virus (HIV) is
replicated once inside helper T cells
(TH cells). (4)

A
  1. RNA converted into DNA using reverse transcriptase;
    Reject ‘messenger’ or ‘m’ before RNA
  2. DNA incorporated/inserted into (helper T cell) DNA/chromosome/genome/nucleus;
  3. DNA transcribed into (HIV m)RNA;
    Accept descriptions of transcription
  4. (HIV mRNA) translated into (new) HIV/viral proteins (for assembly into viral particles);
21
Q

Explain how HIV affects the
production of antibodies when AIDS
develops in a person. (3)

A
  1. Less/no antibody produced;
  2. (Because HIV) destroys helper T cells;
    Accept ‘reduces number’ for ‘destroys’
  3. (So) few/no B cells activated / stimulated
    OR
    (So) few/no B cells undergo mitosis/differentiate/form plasma cells;
22
Q

Describe the structure of the
human immunodeficiency virus
(HIV).(4)

A
  1. RNA (as genetic material);
    Reject nucleus/DNA/plasmids.
  2. Reverse transcriptase;
  3. (Protein) capsomeres/capsid;
    Reject capsule.
  4. (Phospho)lipid (viral) envelope
    OR
    Envelope made of membrane;
    Reject if HIV has a cell membrane or a cell wall.
  5. Attachment proteins;
23
Q

What is a monoclonal antibody?
(3)

A
  1. Antibody specific/complementary to one antigen only
  2. Antibodies all the same and from one original plasma cell
  3. Derived from a hybridoma cell/fused B lymphocyte and cancer cell
24
Q

Suggest monoclonal antibodies
help scientists to identify target cells (4)

A
  1. antigen in cell-surface membrane;
  2. Antibody is complementary;
  3. (So) binds/attaches to the ZO-1/protein;
  4. (Cells identified with) dye/stain/fluorescent marker linked to antibody;
25
Q

Suggest how one antibody can
bind two different molecules (2)

A
  1. have a similar shape/structure;
  2. Antibody is complementary to both
26
Q

Explain why antibody will only bind to target cell

A
  1. antibody has a (specific) tertiary structure;
  2. Has binding site / variable region that only binds to / complementary to one antigen;
  3. Antigen to this antibody (only) found on these nerve cells;
  4. So, antibody (only) binds to / forms antigen-antibody complex with these cells
27
Q

Describe the role of antibodies
in producing a positive result in an
ELISA test.(4)

A
  1. (First) antibody binds/attaches /complementary (in shape) to antigen;
  2. (Second) antibody with enzyme attached is added;
  3. (Second) antibody attaches to antigen;
    Accept (second) antibody attaches to (first) antibody (indirect ELISA test).
  4. (Substrate/solution added) and colour changes;

A-LEVEL AQA- BIOLOGY (38 decks)

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