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Unit 2: Maintaining the internal environment
Quick questions on Vaccines, herd immunity and antibiotic resistance (QCE Biology Unit 2)
11short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is how vaccines work?Show answer
A vaccine introduces antigens from a pathogen in a form that cannot cause serious disease. The immune system treats the antigens as if they were the real pathogen and mounts a primary adaptive response (see innate and adaptive immunity):
What is herd immunity?Show answer
When a high proportion of a population is immune to a pathogen, susceptible individuals are indirectly protected because chains of transmission cannot sustain themselves. This is herd immunity (or community immunity).
What is antibiotic resistance?Show answer
Antibiotics are drugs that kill bacteria (bactericidal) or stop them growing (bacteriostatic). Different classes have different targets: cell wall synthesis (penicillins, cephalosporins), protein synthesis (tetracyclines, macrolides), DNA replication (quinolones), folate metabolism (sulfonamides).
What is mechanisms of resistance?Show answer
- Alteration of the antibiotic's target (modified penicillin-binding protein in MRSA). - Production of enzymes that inactivate the antibiotic (beta-lactamases hydrolyse penicillin). - Efflux pumps that export the antibiotic out of the cell.
What is practices that accelerate resistance?Show answer
- Patients stopping antibiotic courses early. - Prescribing antibiotics for viral infections (which they cannot treat). - Routine use of antibiotics in livestock as growth promoters.
What is implications for human health?Show answer
- "Superbugs" such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE) and multi-drug-resistant tuberculosis (MDR-TB) are major causes of hospital-acquired infection. - Surgery and chemotherapy depend on effective antibiotics; rising resistance threatens to make routine procedures dangerous again. - The WHO has identified antimicrobial resistance as one of the top global public health threats.
What is slowing resistance?Show answer
- Antibiotic stewardship: prescribe only when needed, use the right drug at the right dose, finish the full course. - Infection control: hand hygiene, isolation of infected patients, vaccination to reduce demand for antibiotics. - New drug development and alternative therapies (bacteriophage therapy, monoclonal antibodies).
What is saying vaccines "fight off the pathogen"?Show answer
The vaccine itself does not fight off anything; it triggers an adaptive response and leaves memory cells.
What is confusing antibiotic and antiviral?Show answer
Antibiotics target bacteria; antivirals target viruses. They are not interchangeable, and prescribing antibiotics for a viral illness drives resistance without helping the patient.
What is treating resistance as caused by antibiotics directly?Show answer
Antibiotics select for pre-existing resistant variants; they do not create resistance through induction. The variation arises by chance through mutation; antibiotics are the selective agent.
What is forgetting horizontal gene transfer?Show answer
Bacteria can swap resistance genes across species. This is why resistance can spread faster than a simple parent-to-offspring model predicts.