3. Infection and Response

Pathogen

Microorganisms that cause infectious disease (viruses, bacteria, protists, fungi)

How pathogens spread

Direct contact, water, air (droplets)

Bacteria reproduction

Rapid inside body, produce toxins that damage tissues

Virus reproduction

Live and reproduce inside cells, cause cell damage

Measles symptoms

Fever and red skin rash, spread by droplets from coughs/sneezes

HIV spread

Sexual contact or body fluids (e.g., blood, needles)

Tobacco Mosaic Virus

Plant virus causing mosaic leaf pattern, reducing photosynthesis

Salmonella spread

Contaminated food, causes food poisoning symptoms

Gonorrhoea symptoms

Yellow/green discharge, pain on urination, spread sexually

Rose Black Spot

Fungal disease with black spots on leaves, spread by water/wind

Malaria vector

Mosquito transmits protist causing fever and can be fatal

Non-specific defence: skin

Physical barrier preventing pathogen entry

Non-specific defence: nose

Mucus traps pathogens

Non-specific defence: trachea/bronchi

Cilia and mucus remove pathogens

Non-specific defence: stomach

Acidic environment kills pathogens

White blood cells role

Phagocytosis, antibody production, antitoxin production

Vaccination

Injection of dead/inactive pathogen to stimulate immunity

Antibiotics

Kill bacteria, not effective against viruses

Antibiotic resistance

When bacteria evolve to survive antibiotic treatment

Painkillers

Relieve symptoms but don’t kill pathogens

Digitalis source

Heart drug from foxglove plant

Aspirin source

Painkiller from willow plant

Penicillin source

Antibiotic from Penicillium mould discovered by Fleming

Preclinical testing

Lab tests on cells, tissues, animals for toxicity and efficacy

Clinical trials

Human testing for safety, dosage; includes double-blind trials with placebos