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AQA A Level Biology > Immunity Exam Qs > Flashcards

Immunity Exam Qs Flashcards

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1
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 marks)

A
  1. Cell ingests/engulfs the antibody/ADC
    OR
    Cell membrane surrounds the antibody/ADC (to take it inside the cell);
    Accept endocytosis for ingest/engulf
  2. Lysosomes fuse with vesicle/phagosome (containing ADC);
  3. Lysozymes breakdown/digest the antibody/ADC to release the drug;
    Accept hydrolytic enzyme for lysozyme
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2
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 marks)

A
  1. ADC will bind to non-tumour/healthy cells;
    Reject reference to active site
  2. Cause death/damage of non-tumour/healthy cells
    OR
    Cause damage to other organs/systems;
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3
Q

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

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);
    Accept descriptions of translation Accept named viral protein, eg capsid Reject viral cells
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4
Q

HIV-1 is the most common type of HIV. HIV-1 binds to a receptor on TH cells called CCR5.
Current treatment for HIV-1 involves the use of daily antiretroviral therapy (ART) to stop the virus being replicated. Only 59% of HIV-positive individuals have access to ART.
Scientists have found that two HIV-1-positive patients (P and Q) have gone into remission (have no detectable HIV-1). This happened after a blood stem cell transplant (BSCT).

  • Patient P was given two BSCTs, and patient Q was given one BSCT.
  • All BSCTs came from a donor with TH cells without the CCR5 receptor.
  • In addition, patient P had radiotherapy, and patient Q had chemotherapy.
    Both of these treatments are toxic.
  • Both patients (P and Q) stopped receiving ART 16 months after BSCT.
    18 months after stopping ART, both patients had no HIV-1 RNA in their plasma, no HIV-1 DNA in their TH cells and no CCR5 on their TH cells.

Use the information given to evaluate the use of BSCT to treat HIV infections (5 marks)

A

Max 4 for reasons for or against

For
1. (There appears to be) no virus/ HIV(-1)/RNA/DNA, so could be a cure/effective;
Ignore virus is killed
2. No CCR5/receptor, so not get HIV(-1) in the future
OR
No CCR5/receptor, so nothing for HIV(-1) to bind to;
Reject less CCR5/less HIV(-1) bind
3. Only one transplant/BSCT needed (shown by patient Q)
4. Would not need (daily) ART (16 months after BSCT);

Against
5. Don’t know if chemotherapy/radiotherapy is needed
OR
Do not know if BSCT alone would be effective;
OR
Do not know which treatment is having the effect
OR
Could be due to chemotherapy/radiotherapy;
Accept: chemotherapy/radiotherapy is toxic/harmful/has side-effects
6. Only for HIV-1;
Accept: Might not work in other types of HIV
7. Don’t know if it would work in all people
OR
Only worked/tried in 2 cases;
8. Might not be long term
OR
Only 18 months;
9. HIV-1 may mutate and be able to bind to a different receptor (on TH cells);
10.Might be a lack of (suitable stem cell/BSCT) donors;
Accept stem cells/BSCT (might be) rejected

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5
Q

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

A
  1. Engulfs;
    Accept endocytosis
    OR
    Description Ignore ‘taken in’
  2. Forming vesicle/phagosome and fuses with lysosome;
  3. Enzymes digest/hydrolyse;
    Accept lysozymes for ‘enzymes’
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6
Q

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

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/So) few/no B cells undergo mitosis/differentiate/form plasma cells;
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7
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. (2 marks)

A
  1. Mutation in the viral DNA/RNA/genome/genetic material;
    Accept named examples mutations
  2. Altered (tertiary structure of the) viral attachment protein;
    Accept ‘antigen’ for ‘attachment protein’
    Accept causes antigenic variability
  3. Allows it/attachment protein/virus to bind (to receptors of other species);
    Accept descriptions of binding eg is complementary
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8
Q

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

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);
    reject if answer suggestd vaccine contains antibodies
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9
Q

Describe how the B lymphocytes of a frog would respond to vaccination against Ranavirus.
You can assume that the B lymphocytes of a frog respond in the same way as B lymphocytes of a human.
Do not include details of the cellular response in your answer. (3 marks)

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;
    Accept B cell undergoes clonal selection/expansion
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10
Q

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

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;
  4. (Substrate/solution added) and colour changes
    only award if enzyme is mentioned
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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. (2 marks)

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;
    Reject clotting
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12
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 marks)

A
  1. (Antivenom/Passive immunity) antibodies bind to the toxin/venom/antigen and (causes) its destruction;
    For ‘bind’ accept ‘attach’, ignore ‘attack’.
    For ‘destruction of toxin’ accept agglutination or phagocytosis.
    Ignore reference to antibodies ‘neutralising toxin/stopping damage’
    Reject reference to ‘killing’ toxin/venom.
  2. Active immunity would be too slow/slower;
    Accept ‘passive immunity is faster’, not simply ‘passive immunity is fast’.
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13
Q

A mixture of venoms from several snakes of the same species is used. Suggest why. (2 marks)

A
  1. May be different form of antigen/toxin (within one species)
    OR
    Snakes (within one species) may have different mutations/alleles;
  2. Different antibodies (needed in the antivenom)
    OR
    (Several) antibodies complementary (to several antigens);
    No mark points are available for answers related to collecting venom from different species of snake.
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14
Q

Horses or rabbits can be used to produce antivenoms.
When taking blood to extract antibody, 13 cm3 of blood is collected per kg of the animal’s body mass.
The mean mass of the horses used is 350 kg and the mean mass of the rabbits used is 2 kg
Using only this information, suggest which animal would be better for the production of antivenoms.
Use a calculation to support your answer. (2 marks)

A
  1. Horses because more antivenom/antibodies could be collected (as more blood collected);
  2. 4550 (cm3) v 26 (cm3) (blood collected);
    Accept 175 rabbits needed to (collect the volume of blood from) one horse.
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15
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 marks)

A
  1. B cells specific to the venom reproduce by mitosis;
    Accept in context of primary or secondary immune response.
    Credit idea of specificity if given once in relation to T or B cell.
    Accept a description for specificity. Accept ‘clone’ for ‘reproduce by mitosis’. ‘Clonal selection of B cells’ = MP1.
  2. (B cells produce) plasma cells and memory cells;
  3. The second dose produces antibodies (in secondary immune response) in higher concentration and quickly
    OR
    The first dose must be small so the animal is not killed;
    Accept ‘a lot of antibody’ for ‘higher concentration of antibody’.
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16
Q

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

A
  1. Phagosome / vesicle fuses with lysosome;
    Accept vacuole fuses with lysosome
    Reject virus fuses with lysosome
  2. (Virus) destroyed by lysozymes / hydrolytic enzymes;
  3. Peptides / antigen (from virus) are displayed on the cell membrane;
17
Q

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

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;
  5. and 2. ‘Helper’ is required once only.
  6. Accept ‘This (helper) T cell stimulates a
    competent B cell’
    ‘T cell stimulates B cell to undergo clonal selection’. This statement achieves mp2 and mp3.
18
Q

Collagen is a protein produced by cells in joints, such as the knee.
Rheumatoid arthritis (RA) is an auto-immune disease. In an auto-immune disease, a person’s immune system attacks their own cells. RA causes pain, swelling and stiffness in the joints.
Scientists have found a virus that produces a protein very similar to human collagen.
Suggest how the immune response to this viral protein can result in the development of RA. (2 marks)

A
  1. The antibody against virus (antigen) will bind to collagen;
  2. This results in the destruction of the (human) cells / collagen;
    ignore attacks
19
Q

What is an antigen? (2 marks;

A
  1. Foreign protein;
    *accept glycoprotein/glycolipid/polysaccharide
  2. (that) stimulates an immune response / production of antibody;
20
Q

What is an antibody (2 marks)

A
  1. A protein / immunoglobulin specific to an antigen;
  2. Produced by B cells
    OR
    Secreted by plasma cells
21
Q

Bacterial meningitis is a potentially fatal disease affecting the membranes around the brain. Neisseria meningitidis (Nm) is a leading cause of bacterial meningitis.

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

A
  1. Antigen / epitope on surface of N. meninigitidis / bacterium binds to surface protein / surface receptor on a (specific / single) B cell.
    If answered in context of T cell, allow Antigen binds to (specific / single) T cell
  2. (Activated) B cell divides by mitosis / produces clone;
    If answered in context of T cell, allow (Activated) T cell releases cytokine.
  3. (Division) stimulated by cytokines / by T cells;
    If answered in context of T cell, allow (Cytokine) stimulates production of plasma cells;
  4. B cells / plasma cells release antibodies;
  5. (Some) B cells become memory cells;
  6. Memory cells produce plasma / antibodies faster
22
Q

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

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 secretes large amounts of antibody;
  7. B cell divides to form clone all secreting / producing same antibody.
23
Q

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

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.
24
Q

A mutation of a tumour suppressor gene can result in the formation of a tumour.
Explain how.

A
  1. (Tumour suppressor) gene inactivated / not able to control / slow down cell division;
    Ignore: references to growth
  2. Rate of cell division too fast / out of control.
    1 and 2 Accept: mitosis
    1 and 2 Reject: meiosis
25
Q

The percentage of the population vaccinated does not need to be 100% to be effective in preventing the spread of whooping cough.
Suggest why.

A
  1. More people are immune / fewer people carry the pathogen;
    If neither point 1 or 2 awarded
    Herd immunity = 1 mark

Unvaccinated does not mean infected
Q Do not accept disease for pathogen
2. So susceptible / unvaccinated people less likely to contact infected
people.

26
Q

Putting bee honey on a cut kills bacteria. Honey contains a high concentration of sugar.
Use your knowledge of water potential to suggest how putting honey on a cut kills
bacteria.

A
  1. Water potential in (bacterial) cells higher (than in honey) / water potential in honey lower (than in bacterial cells);
    Q candidates must express themselves clearly
    Must be comparative e.g. high WP in cell and low WP in
    honey
  2. Water leaves bacteria / cells by osmosis;
  3. (Loss of water) stops (metabolic) reactions.
  4. Needs a reason why lack of water kills the cell
27
Q

Some cancer cells have a receptor protein in their cell-surface membrane that binds to a hormone called growth factor. This stimulates the cancer cells to divide.
Scientists have produced a monoclonal antibody that stops this stimulation. Use your knowledge of monoclonal antibodies to suggest how this antibody stops the growth of a tumour.

A
  1. Antibody has specific tertiary structure / binding site / variable region;
    Do not accept explanations involving undefined antigen
  2. Complementary (shape / fit) to receptor protein / GF / binds to receptor
    protein / to GF;
    Ignore: same shape as receptor protein / GF
  3. Prevents GF binding (to receptor).
28
Q

Give two ways in which pathogens can cause disease.

A
  1. (Releases) toxins;
  2. Kills cells / tissues.
  3. Accept any reference to cell / tissue damage
    Ignore infecting / invading cells

AQA A Level Biology (12 decks)

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