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Biology > 2.4 - Cell recognition and the immune system > Flashcards

2.4 - Cell recognition and the immune system Flashcards

1
Q

Describe how HIV is replicated. (4)

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

ADCs are molecules made of a monoclonal antibody linked to a cancer drug. Figure 1 shows how an ADC enters and kills a tumour cell. The process of entering the cell and the breakdown of the antibody to release the drug is very similar to phagocytosis.
Use your knowledge of phagocytosis to describe how an ADC enters and kills the tumour cell. (3)

A
  • Cell ingests/engulfs the antibody/ADC
    / Cell membrane surrounds the antibody/ADC (to take it inside the cell
    ‘ accept endocytosis for ingest/engulf’
  • Lysosomes fuse with vesicle/phagosome (containing ADC)
  • Lysozymes breakdown/digest the antibody/ADC to release the drug
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3
Q

Some of the antigens found on the surface of tumour cells are also found on the surface of healthy human cells. Use this information to explain why treatment with an ADC often causes side effects. (2)

A
  • ADC will bind to non-tumour/healthy cells
    Reject reference to active site
  • Cause death/damage of non-tumour/healthy cells
    /Cause damage to other organs/systems
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4
Q

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

A
  • RNA converted into DNA using reverse transcriptase
    Reject ‘messenger’ or ‘m’ before RNA
  • DNA incorporated/inserted into (helper T cell)
    DNA/chromosome/genome/nucleus
  • DNA transcribed into (HIV m)RNA
    Accept descriptions of transcription
  • (HIV mRNA) translated into (new) HIV/viral proteins (for
    assembly into viral particles)
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5
Q

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

A
  • Engulfs ‘accept endocytosis’
  • Forming vesicle/phagosome and fuses with lysosome
  • Enzymes digest/hydrolyse
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6
Q

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

A
  • (Cells from) other organisms/transplants
  • Abnormal/cancer/tumour (cells)
  • (Cells) infected by virus
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7
Q

What is the role of the disulfide bridge in forming the quaternary structure of an antibody? (1)

A
  • Joins two (different) polypeptides
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8
Q

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

A
  • Less/no antibody produced
  • (Because HIV) destroys helper T cells
  • (So) few/no B cells activated / stimulated
    /(So) few/no B cells undergo mitosis/differentiate/form plasma cells
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9
Q

In Europe, viruses have infected a large number of frogs of different species. The viruses are closely related and all belong to the Ranavirus group. Previously, the viruses infected only one species of frog. Suggest and explain how the viruses became able to infect other species of frog. (3)

A
  • Mutation in the viral DNA/RNA/genome/genetic material
    Accept named examples mutations
  • Altered (tertiary structure of the) viral attachment protein
    ‘accept antigen for attachment protein’
    ‘accept causes antigenic variability’
  • Allows it/attachment protein/virus to bind (to receptors of other species)
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10
Q

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

A
  • (The scientists) could identify proteins (that derive from the genetic code)
    /(The scientists) could identify the proteome
  • (They) could (then) identify potential antigens (to use in the vaccine)
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11
Q

Describe how the B lymphocytes of a frog would respond to vaccination against Ranavirus. (3)

A
  • B cell (antibody) binds to (viral) specific/complementary
    receptor/antigen
    ‘accept B cell forms antigen-antibody complex
  • B cell clones / B cell divides by mitosis
  • Plasma cells release/produce (monoclonal) antibodies (against the virus)
  • (B/plasma cells produce/develop) memory cells
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12
Q

What is a monoclonal antibody? (1)

A
  • (Antibodies with the) same tertiary structure
  • (Antibody produced from) identical/cloned plasma cells/B cells/B lymphocytes
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13
Q

After a disease is diagnosed, monoclonal antibodies are used in some medical treatments. Give one example of using monoclonal antibodies in a medical treatment. (1)

A
  • Targets/binds/carries drug/medicine to specific cells/ antigens/receptors
  • Block antigens/receptors on cells
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14
Q

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

A
  • (First) antibody binds/attaches/complementary (in shape) to antigen
  • (Second) antibody with enzyme attached is added
  • (Second) antibody attaches to antigen
    ‘accept (second) antibody attaches to (first) antibody (indirect ELISA test)’
  • (Substrate/solution added) and colour changes
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15
Q

Describe and explain the role of antibodies in stimulating phagocytosis. (2)

A
  • Bind to antigen /are markers
    ‘accept form (antibody-antigen) complexes/are
    complementary to antigen’
  • (Antibodies) cause clumping/agglutination which attracts phagocytes
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16
Q

When a person is bitten by a venomous snake, the snake injects a toxin into the person. Antivenom is injected as treatment. Antivenom contains antibodies against the snake toxin. This treatment is an example of passive immunity. Explain how the treatment with antivenom works and why it is essential to use passive immunity, rather than active immunity. (2)

A
  • (Antivenom/Passive immunity) antibodies bind to the
    toxin/venom/antigen and (causes) its destruction
    ‘accept attach for bind’
    ‘accept agglutination/phagocytosis for destruction of toxin’
  • Active immunity would be too slow/slower
17
Q

During vaccination, each animal is initially injected with a small volume of venom. Two weeks later, it is injected with a larger volume of venom. Use your knowledge of the humoral immune response to explain this vaccination programme. (3)

A
  • B cells specific to the venom reproduce by mitosis
  • (B cells produce) plasma cells and memory cells
  • The second dose produces antibodies (in secondary immune response) in higher concentration and quickly
    / The first dose must be small so the animal is not killed
18
Q

Describe how phagocytosis of a virus leads to presentation of its antigens. (3)

A
  • Phagosome / vesicle fuses with lysosome
  • (Virus) destroyed by lysozymes / hydrolytic enzymes
  • Peptides / antigen (from virus) are displayed on the cell membrane
19
Q

Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen. (3)

A
  • Helper T cell / TH cell binds to the antigen (on the antigen presenting cell / phagocyte)
  • This helper T / TH cell stimulates a specific B cell
  • B cell clones / B cell divides by mitosis
  • (Forms) plasma cells that release antibodies
20
Q

What is an antigen? (2)

A
  • Foreign protein
    ‘accept glycoprotein / glycolipid / polysaccharide’
  • (that) stimulates an immune response / production of antibody
21
Q

What is an antibody? (2)

A
  • A protein / immunoglobulin specific to an antigen
  • Produced by B cells / Secreted by plasma cells
22
Q

In the UK, children are vaccinated against this disease. Describe how vaccination can lead to protection against bacterial meningitis. (6)

A
  • Antigen on surface of the bacterium binds to surface protein/ surface receptor on a (specific / single) B cell
    ‘allow Antigen binds to (specific / single) T cell’
  • (Activated) B cell divides by mitosis / produces clone
    ‘allow (Activated) T cell releases cytokine’
  • (Division) stimulated by cytokines / by T cells
    ‘allow (Cytokine) stimulates production of plasma cells’
  • B cells / plasma cells release antibodies
  • (Some) B cells become memory cells
  • Memory cells produce plasma / antibodies faster
23
Q

When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how. (5)

A
  • Vaccine contains antigen from pathogen
  • Macrophage presents antigen on its surface
  • T cell with complementary receptor protein binds to antigen
  • T cell stimulates B cell
  • (With) complementary antibody on its surface
  • B cell secretes large amounts of antibody
  • B cell divides to form clone all secreting / producing same
    antibody
24
Q

Describe the difference between active and passive immunity. (5)

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

Biology (40 decks)

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