DiseaseEdexcel GCSE Biology: Revision notes

Section 1

Health and Disease

WHO defines health as complete physical, mental and social well-being, not just absence of disease.

Type	Definition
Communicable	Caused by a pathogen, spreads between organisms
Non-communicable	Cannot be transmitted

One disease can increase susceptibility to others (e.g. HIV weakens immunity to other infections).

Key termsHealthCommunicable diseaseNon-communicable disease

Common mistake

Health includes mental AND social well-being, not just 'not being ill'.

Section 2

Pathogens and Named Diseases

Disease	Pathogen	Effect
Cholera	Bacteria	Diarrhoea
TB	Bacteria	Lung damage
Stomach ulcers	Bacteria (Helicobacter)	Stomach lining damage
Chalara ash dieback	Fungi	Leaf loss/bark lesions
Malaria	Protists	Blood/liver damage
HIV	Virus	Destroys WBCs → AIDS
Ebola	Virus	Haemorrhagic fever

Key termsPathogenAIDS

Section 3

Spread and Prevention

Cholera: water. TB: airborne. Chalara: airborne. Malaria: vectors (mosquitoes). Stomach ulcers: oral. Ebola: body fluids. Prevention targets the specific route (clean water, vaccination, nets, hygiene, isolation).

Key termsVector

Section 4

Viral Lifecycle

Lytic pathway: virus injects genetic material, host makes new viruses, host lyses. Lysogenic pathway: viral DNA inserts into host chromosome, replicated as cell divides, dormant, may later switch to lytic.

Key termsLytic pathwayLysogenic pathway

Section 5

Sexually Transmitted Infections

Chlamydia (bacteria) and HIV (virus) spread via sexual contact; prevention via condoms and screening.

Key termsSTI

Section 6

Plant Defences and Disease Detection

Physical: cell wall, cuticle. Chemical: antibacterial compounds (some used in human medicine).

Detection: eliminate environmental causes, distribution analysis, observe symptoms, diagnostic testing.

Key termsCuticle

Example

Willow bark contains a compound related to aspirin.

Must Know

Health (WHO) = physical, mental, social well-being.
Communicable vs non-communicable.
Know all 7 named diseases, pathogen type, spread route.
Viral lytic (burst) vs lysogenic (dormant) pathways.
Plants: cell wall/cuticle physical; chemicals for defence.
Plant disease detection: elimination, distribution, symptoms, diagnostics.

That's the notes covered.

Carry on to the next subtopic.