Health Disease and Medicine – Edexcel GCSE Biology Revision Notes

What you'll learn

This topic examines how diseases affect human health, the distinction between communicable and non-communicable diseases, and how modern medicine prevents and treats illness. Edexcel GCSE Biology papers frequently test your understanding of disease transmission, immune responses, antibiotic resistance, and lifestyle factors affecting health. Expect questions requiring data interpretation, evaluating treatments, and explaining biological mechanisms.

Key terms and definitions

Health — the state of physical and mental wellbeing, not merely the absence of disease.

Disease — a condition that impairs the normal functioning of the body or mind.

Communicable disease — an infectious disease caused by pathogens that can be transmitted between individuals (e.g. tuberculosis, malaria, HIV).

Non-communicable disease — a disease that cannot be transmitted between individuals, often chronic and developing over time (e.g. cardiovascular disease, Type 2 diabetes, cancer).

Pathogen — a microorganism that causes disease, including bacteria, viruses, fungi and protists.

Antibiotics — medicines that kill or inhibit the growth of bacteria but are ineffective against viruses.

Vaccination — the administration of antigenic material to stimulate immunity against a specific pathogen without causing disease.

Herd immunity — when a large percentage of a population is immune to a disease, reducing transmission and protecting vulnerable individuals.

Core concepts

Communicable diseases and pathogens

Pathogens cause communicable diseases through infection. The four main types tested in Edexcel GCSE Biology are:

Bacteria — prokaryotic cells that reproduce rapidly inside the body, causing damage by producing toxins. Examples include:

Salmonella causing food poisoning through contaminated food, producing fever, cramps and vomiting
Gonorrhoea, a sexually transmitted disease causing painful urination and thick discharge

Viruses — non-living particles that invade host cells and use cellular machinery to replicate, destroying cells in the process. Examples include:

Measles spreading through droplet infection, causing fever, rash and potentially fatal complications
HIV transmitted through bodily fluids, attacking immune cells and potentially progressing to AIDS
Tobacco Mosaic Virus (TMV) infecting tobacco plants, causing mosaic patterns on leaves and reduced photosynthesis

Protists — eukaryotic organisms, often parasitic. Example:

Plasmodium causing malaria, transmitted by mosquito vectors, causing recurring fever and potentially fatal organ damage

Fungi — organisms spreading through spores. Example:

Rose black spot infecting rose plants, causing purple-black spots on leaves, reducing photosynthesis

Disease transmission and prevention

Pathogens spread through multiple routes:

Direct contact — touching infected individuals or contaminated surfaces (e.g. athlete's foot fungus)

Droplet infection — inhaling droplets from coughs and sneezes (e.g. influenza, tuberculosis)

Contaminated food and water — consuming materials containing pathogens (e.g. cholera bacteria, Salmonella)

Vector transmission — organisms carrying pathogens between hosts (e.g. mosquitoes transmitting malaria)

Prevention strategies reduce transmission:

Improving hygiene: handwashing, sterilising water, proper food preparation
Isolating infected individuals: quarantine prevents disease spread
Destroying vectors: insecticides, mosquito nets, removing standing water
Vaccination programmes: stimulating population immunity
Using contraception: barrier methods prevent STD transmission

The immune system and defence mechanisms

The body employs multiple defence layers:

Physical barriers prevent pathogen entry:

Skin provides a waterproof, protective barrier
Nose hair and mucus trap particles
Trachea and bronchi produce mucus that traps pathogens; cilia move mucus upward for removal
Stomach acid (pH 2) destroys ingested pathogens

Immune response when pathogens breach barriers:

Phagocytosis: white blood cells (phagocytes) engulf and digest pathogens
Antibody production: lymphocytes detect antigens (proteins on pathogen surfaces) and produce specific antibodies that bind to antigens, marking pathogens for destruction
Antitoxin production: lymphocytes produce antitoxins that neutralise toxins released by bacteria
Memory cells: after infection, some lymphocytes remain as memory cells, enabling rapid antibody production if the same pathogen reinvades

Vaccination and herd immunity

Vaccines contain:

Dead or inactive pathogens
Live attenuated (weakened) pathogens
Pathogen fragments or toxins

The vaccination process:

Vaccine injected containing antigens
Lymphocytes detect antigens and produce specific antibodies
Memory cells remain in the bloodstream
Upon actual infection, memory cells rapidly produce large quantities of antibodies
Pathogens destroyed before symptoms develop

Edexcel GCSE Biology examines herd immunity principles: when approximately 90-95% of a population is vaccinated against diseases like measles, transmission chains break because insufficient susceptible hosts exist. This protects individuals who cannot be vaccinated (babies, immunocompromised people).

Antibiotics and antibiotic resistance

Antibiotics kill bacteria or prevent their reproduction by:

Inhibiting cell wall synthesis
Disrupting protein production
Interfering with DNA replication

Crucial understanding for Edexcel GCSE Biology: antibiotics are ineffective against viruses because viruses lack cellular structures and metabolic processes to target.

Antibiotic resistance develops through natural selection:

Bacterial populations contain genetic variation through mutation
Some bacteria possess alleles conferring antibiotic resistance
When antibiotics are used, susceptible bacteria die
Resistant bacteria survive and reproduce
Resistance alleles increase in frequency
Entire populations become resistant (e.g. MRSA — methicillin-resistant Staphylococcus aureus)

Reducing antibiotic resistance:

Completing prescribed courses (prevents partially resistant bacteria surviving)
Doctors prescribing antibiotics only for bacterial infections
Restricting agricultural antibiotic use
Developing new antibiotics (challenging as bacteria evolve resistance faster than drug development)

Non-communicable diseases

Non-communicable diseases cannot spread between individuals but significantly impact health:

Cardiovascular disease results from lifestyle and genetic factors:

High blood pressure, high cholesterol, smoking, obesity, inactivity increase risk
Atherosclerosis: fatty deposits (plaques) accumulate in arteries, restricting blood flow
Heart attacks occur when coronary arteries become blocked, depriving heart muscle of oxygen
Strokes result from blocked or burst blood vessels in the brain

Type 2 diabetes develops when:

The body becomes resistant to insulin
Pancreas cannot produce sufficient insulin
Blood glucose levels remain elevated
Risk factors: obesity, poor diet, inactivity, genetic predisposition

Cancer arises from uncontrolled cell division:

Mutations in genes controlling cell division create tumours
Benign tumours remain localised, usually non-life-threatening
Malignant tumours invade tissues and metastasise (spread) through bloodstream
Risk factors: smoking (lung cancer), UV exposure (skin cancer), genetic factors, viral infections (HPV causing cervical cancer)

Obesity and diet-related conditions:

BMI (Body Mass Index) = mass (kg) ÷ height² (m²)
BMI >30 indicates obesity
Increases risk of Type 2 diabetes, cardiovascular disease, joint problems, certain cancers

Lifestyle factors and disease interaction

Edexcel GCSE Biology emphasises disease interaction:

Immune system defects increase infection susceptibility (HIV destroys immune cells, making individuals vulnerable to tuberculosis and other infections)
Viruses triggering cancer: HPV causes cervical cancer; hepatitis viruses cause liver cancer
Physical ill health affecting mental health: chronic diseases cause depression and anxiety
Malnutrition weakening immunity: vitamin deficiencies impair immune function

Modern medicine and drug development

Drug discovery sources:

Plants: aspirin from willow bark, digitalis from foxgloves (heart medication)
Microorganisms: penicillin from Penicillium mould
Synthetic production: laboratory-created compounds

Preclinical testing:

Computer models predict drug effectiveness and toxicity
Cell and tissue culture testing
Animal testing for efficacy, toxicity and dosage

Clinical trials:

Phase 1: healthy volunteers, testing safety and dosage
Phase 2: small patient groups, testing effectiveness
Phase 3: large patient groups, comparing against existing treatments
Double-blind trials: neither patients nor doctors know who receives the actual drug versus placebo, eliminating bias

Placebos (inactive substances) used as controls because psychological factors can influence perceived recovery.

Worked examples

Example 1: A student investigated the effect of antibiotics on bacterial growth. She placed paper discs soaked in different antibiotics onto an agar plate covered with bacteria. After 24 hours, she measured the clear zones around each disc.

Explain why clear zones appeared around the antibiotic discs. [2 marks]

Answer: The antibiotics diffused through the agar [1]. The antibiotics killed the bacteria or prevented their reproduction, creating zones where no bacteria grew [1].

Example 2: The graph shows measles cases in a country before and after a vaccination programme began in 1968.

Explain why measles cases decreased dramatically after 1968. [3 marks]

Answer: Vaccination exposed individuals to measles antigens without causing disease [1]. This stimulated antibody production and created memory cells [1]. When vaccinated individuals encountered actual measles virus, memory cells rapidly produced antibodies, preventing infection and reducing disease transmission through herd immunity [1].

Example 3: A doctor prescribes a 7-day course of antibiotics for a bacterial chest infection. The patient feels better after 3 days and stops taking the antibiotics.

Explain why stopping antibiotic treatment early contributes to antibiotic resistance. [3 marks]

Answer: Not all bacteria are killed after only 3 days [1]. Bacteria with some resistance survive and reproduce [1]. These partially resistant bacteria pass resistance alleles to offspring, and repeated incomplete treatments select for fully resistant populations [1].

Common mistakes and how to avoid them

Mistake: Stating antibiotics kill viruses or cure viral infections like flu. Correction: Antibiotics only work against bacteria because they target bacterial cell structures and processes that viruses lack. Viral diseases are treated with antivirals or vaccines, not antibiotics.
Mistake: Confusing immunity with resistance. Correction: Immunity refers to the body's ability to recognise and destroy pathogens through antibodies and memory cells. Antibiotic resistance describes bacteria that have evolved alleles enabling survival despite antibiotic presence.
Mistake: Claiming vaccines contain the actual disease. Correction: Vaccines contain dead, weakened or fragmented pathogens carrying antigens. These cannot cause disease but stimulate immune response and memory cell production.
Mistake: Writing that non-communicable diseases are caused by pathogens. Correction: Non-communicable diseases result from genetic factors, lifestyle choices (diet, exercise, smoking), environmental factors or combinations, not pathogen infection.
Mistake: Stating all tumours are cancer. Correction: Only malignant tumours are cancerous (invading tissues and metastasising). Benign tumours remain contained and rarely life-threatening.
Mistake: Explaining natural selection without mentioning variation or reproduction. Correction: For antibiotic resistance through natural selection, always state: genetic variation exists through mutation, selection pressure (antibiotics) kills susceptible bacteria, resistant bacteria survive and reproduce, passing resistance alleles to offspring.

Exam technique for Health Disease and Medicine

Command word recognition: "Explain" requires mechanisms (2-3 marks typically award 1 mark per linked point about how/why something occurs). "Describe" requires stating what happens without mechanisms. "Suggest" accepts scientifically reasonable answers not explicitly taught.
Data interpretation questions: When analysing graphs or tables about disease incidence, vaccination rates or antibiotic effectiveness, always quote figures from the data, calculate differences or percentages if asked, and link patterns to biological principles (e.g. herd immunity explaining disease reduction).
Extended response questions: Six-mark questions on this topic often ask you to evaluate vaccination programmes, explain disease prevention strategies, or describe immune responses. Structure answers with clear paragraphs covering different aspects, use precise terminology (antigens, antibodies, lymphocytes, memory cells), and provide named examples.
Practical context: Be prepared for questions referencing core practicals or investigations about antimicrobial substances, aseptic technique, or epidemiological data. Explain variables, controls, safety precautions and how results support conclusions about disease prevention or treatment.

Quick revision summary

Communicable diseases are caused by pathogens (bacteria, viruses, protists, fungi) transmitted through direct contact, droplets, contaminated substances or vectors. The immune system uses physical barriers, phagocytosis and antibody production by lymphocytes. Vaccinations create immunity through memory cells. Antibiotics kill bacteria but not viruses; resistance evolves through natural selection when antibiotics are misused. Non-communicable diseases (cardiovascular disease, Type 2 diabetes, cancer) result from lifestyle and genetic factors. Modern drug development involves preclinical testing and double-blind clinical trials with placebos. Disease interactions occur when one condition increases susceptibility to others.