The Immune System

• Suggest and explain two further investigations that should be done before this ADC is tested on human breast cancer patients.

  1. Test other animals to check for side effects (e.g. rats).
  2. Test healthy humans to check for side effects.
• People given the whole-cell vaccines produced a greater range of antibodies against the bacterium than the people given the vaccines containing parts of the bacterial cells. Explain why.

  They were exposed to a greater range of antigens, each antigen causing its own immune response/production of a specific antibody;
• People given whole-cell vaccines were more likely to develop harmful side effects than people given vaccines containing parts of the bacterial cells. Suggest reasons why.

  The bacteria may be alive, meaning it could reproduce/the bacteria may contain toxins which may be killing the cell.
• Give two structures a bacterial cell may have that a white blood cell does not have.

  1. Cell wall;
  2. Capsule/slime layer;
  3. Circular DNA;
  4. DNA without histones;
  5. Flagellum;
  6. Plasmid;
  7. Pilus;
  8. 70s/smaller ribosomes;
  9. Mesosome;
• The scientists concluded from their test that 4% of patients with long-term coughs had whooping cough.

  Explain how they used the results of their test to reach this conclusion.

  1. Only patients who had whooping cough have toxin/antibody/immune response;
  2. Toxin is an antigen;
  3. Toxin (only) produced by this bacterium;
  4. Leading to the presence of a specific antibody;
  5. Only 4% had this antibody;
• Explain how a blood transfusion from a patient recently recovered from a virus may be an effective treatment.

  There will be a large quantity of antibodies in the transfused blood. They are specific to the virus and will bind with its antigens to destroy the virus (or prevent it entering cells).
• Explain why a high mutation rate makes it difficult to develop a vaccine.

  A high mutation rate leads to antigenic variability. Vaccines contain specific antigens which are not complementary to and therefore will not bind to the changed antigen(s).
• Explain how the treatment with antivenom works and why it is essential to use passive immunity rather than active immunity.

  Antivenom antibodies bind to the venom and destroy it.

  Active immunity would be too much slower than passive immunity.
• When creating an antivenom, why is a mixture of venom from multiple snake species used?

  Different snake venoms may have different antigens or toxins, so therefore different antibodies are needed in the antivenom.
• 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.

  1. B-cells specific to the venom reproduce by mitosis.
  2. The B-cells produce plasma and memory cells.
  3. The second dose produces antibodies (secondary immune response) in high concentrations quickly.
• Suggest and explain how a virus in one animal species could become able to infect other species of animal.

  A mutation in the viral DNA/RNA alters the tertiary structure of the viral attachment proteins/antigens and allows it to bind to the cell receptors of other species.
• Name two techniques scientists may use when analysing viral DNA to determine that two viruses are closely related.

  1. DNA fingerprinting
  2. DNA/genome sequencing
  3. the polymerase chain reaction
• Determining the genome fo a virus could allow scientists to develop a vaccine.

  Explain how.

  The scientists could identify proteins that derive from the genetic code of the virus and therefore could identify potential antigens to use in the vaccine.
• The scientists suggested that people newly diagnosed with this bladder infection should be treated with both the current antibiotic and the new antibiotic.

  Explain why the scientists made this suggestion. Use information from Figure 2 and your knowledge of evolution of antibiotic resistance in bacteria in your answer.

  1. New/old antibiotic does not kill all bacteria;
  2. Resistant bacteria will reproduce to produce more resistant bacteria;
  3. Use of both = one antibiotic will kill bacteria resistant to the other antibiotic;
• A new antibiotic is safe to use in humans because it does not inhibit the ATP synthase found in human cells. Suggest why human ATP synthase is not inhibited and bacterial synthase is inhibited.

  Human ATP synthase has a different tertiary structure to bacterial ATP synthase.

  OR

  Human ATP synthase has a different shape active site to bacterial ATP synthase.