Infection & Response
What's covered
Key facts
Antibiotic Resistance
Antibiotics do not work against influenza or any other viral illness.
Communicable Diseases
Antibiotics kill bacteria or stop them reproducing by damaging cell walls, membranes, or protein synthesis.
Culturing Microorganisms
Aseptic technique is a set of procedures that prevents unwanted microorganisms from contaminating a culture.
Drug Development
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).
Human Defence Systems
Antibodies are proteins that bind to specific antigens on a pathogen, marking it for destruction.
Monoclonal Antibodies
A hybridoma cell (lymphocyte + tumour cell) divides indefinitely and produces a specific antibody.
Named Communicable Diseases
Gonorrhoea is a bacterial sexually transmitted infection that can cause infertility if untreated.
Plant Disease and Defences
Tobacco mosaic virus (TMV) is a plant pathogen that produces a mosaic pattern of discolouration on leaves, reducing photosynthesis and growth.
Antibiotic Resistance
Patients must finish the full course of antibiotics; stopping early leaves resistant bacteria alive to reproduce.
Communicable Diseases
Athlete's foot is a fungal disease affecting the skin (especially between the toes) and nails.
Practice questions with answers
A taste of the 87 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
Why are antibiotics ineffective against viruses?
- •Antibiotics dissolve in water inside cells
- •Viruses are immune to all chemicals
- •Viruses are too small to be targeted
- ✓Viruses lack the cellular structures antibiotics target
Which option correctly matches each type of pathogen to a disease it causes?
- •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?
- ✓Physical barrier preventing pathogen entry
- •Producing white blood cells inside
- •Trapping pathogens in mucus and cilia
- •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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