Infection & Response
What's covered
Key facts
Antibiotics do not work against influenza or any other viral illness.
Antibiotics kill bacteria or stop them reproducing by damaging cell walls, membranes, or protein synthesis.
Aseptic technique is a set of procedures that prevents unwanted microorganisms from contaminating a culture.
Human clinical trials run in phases: Phase 1 uses a small group of healthy volunteers (safety, low dose, side effects); Phase 2 uses patients with the disease (efficacy and dose); Phase 3 uses a large patient group (effectiveness vs existing treatment / placebo).
Antibodies are proteins that bind to specific antigens on a pathogen, marking it for destruction.
A hybridoma cell (lymphocyte + tumour cell) divides indefinitely and produces a specific antibody.
Gonorrhoea is a bacterial sexually transmitted infection that can cause infertility if untreated.
Tobacco mosaic virus (TMV) is a plant pathogen that produces a mosaic pattern of discolouration on leaves, reducing photosynthesis and growth.
Patients must finish the full course of antibiotics; stopping early leaves resistant bacteria alive to reproduce.
Antibiotics do not treat viral infections because they target bacterial cell structures (cell wall, ribosome, DNA gyrase) that viruses lack.
Sample questions
A taste of the 109 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
Why must patients finish a full course of antibiotics?
- •Antibiotics work better when finished
- •It's required by UK law to finish
- •Patients feel better quickly when finished
- ✓Stopping early leaves resistant bacteria alive
What are the four pathogen types? Give a disease example of each.
- •Bacteria (athlete's foot), viruses (Salmonella), fungi (malaria), protists (rose black spot).
- •Bacteria (flu), viruses (rose black spot), fungi (HIV), protists (Salmonella).
- •Bacteria (measles), viruses (cholera), fungi (malaria), protists (TB).
- ✓Bacteria (TB), viruses (flu), fungi (athlete's foot), protists (malaria).
What is the purpose of aseptic technique when culturing microorganisms?
- •Increases the nutrient content of the agar
- •Makes the culture visible under a microscope
- ✓Prevents contamination of a culture by unwanted microbes
- •Speeds up the growth rate of the bacteria
In which stage are drugs tested for the first time on people?
- ✓Clinical trials
- •Manufacturing
- •Marketing
- •Preclinical (cells)
Which non-specific defence is the skin?
- •Killing all bacteria with heat
- ✓Physical barrier preventing pathogen entry
- •Producing white blood cells inside
- •Triggering antibodies on contact
What cell is made when a lymphocyte fuses with a tumour cell?
- ✓A hybridoma — it divides indefinitely and produces specific antibodies.
- •A memory cell — it stays dormant until antigen re-exposure occurs.
- •A phagocyte — it engulfs pathogens but does not make antibodies.
- •A plasma cell — it secretes antibodies but cannot keep dividing.
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