The Immune System & Vaccination
The human body defends itself against disease-causing microorganisms (pathogens) using non-specific physical and chemical barriers alongside the specific immune system. White blood cells destroy invading pathogens through phagocytosis, antibody production, and antitoxin release, while vaccination establishes long-term immunological memory.
- Pathogen
- A microorganism that causes infectious disease.
- Antigen
- A unique protein on the surface of a pathogen that immune cells recognize.
- Antibody
- A protein produced by white blood cells that binds to specific antigens to destroy the pathogen.
Interactive Human Body & Cell Structure Explorer
Click any internal organ or organelle to inspect its structure, toggle organs on/off to see what happens, or test yourself in Quiz Mode.
Heart (Double Circulatory Pump)
Structure & Function:
Pumps blood in a double circulatory system: the right ventricle pumps deoxygenated blood to the lungs, and the thick muscular left ventricle pumps oxygenated blood at high pressure around the whole body.
Key Exam Mark-Scheme Point:
Exam tip: The left ventricle has a much thicker muscular wall than the right ventricle because it must pump blood at high pressure all the way around the entire body, not just to the lungs.
What happens if this organ fails or is removed?
Without pressure from the heart, blood flow stops immediately. Oxygen and glucose cannot reach tissues, and waste carbon dioxide cannot be removed.
Tip: Use the “Simulate Organ Failure” button above to see how each organ system depends on the others to maintain homeostasis and cellular respiration.
Key Concepts & Exam Definitions (6)
- Pathogen
- A microorganism that causes infectious disease.
- Antigen
- A unique protein on the surface of a pathogen that immune cells recognize.
- Antibody
- A protein produced by white blood cells that binds to specific antigens to destroy the pathogen.
- Phagocytosis
- The process where a white blood cell engulfs and digests a pathogen.
- Vaccination
- Injecting dead or inactive pathogens to stimulate antibody production and create memory cells.
- Antibiotics
- Medicines that help to cure bacterial disease by killing infective bacteria inside the body.
Quick-Fire Flashcards (5)
Click any card to check the answer, then mark it as Known to track your progress.
Name four types of pathogen.
Do antibiotics kill viruses?
What do antitoxins do?
What are memory cells?
How do viruses cause illness?
Exam-Style Questions & Mark Schemes (3)
Write or think through your answer first, then click Check Mark Scheme to see the exact points examiners award marks for.
- Q1
Explain how vaccination works to prevent disease.
Click “Check Mark Scheme” to compare your answer, A dead or inactive pathogen is injected. White blood cells detect its antigens and produce specific antibodies. If the live pathogen infects the body later, memory cells rapidly produce antibodies to destroy it before symptoms develop.
- Q2
Describe two ways the body prevents pathogens from entering.
Click “Check Mark Scheme” to compare your answer, The skin acts as a physical barrier. The stomach produces hydrochloric acid which kills pathogens in food and drink.
- Q3
Why is it difficult to develop drugs that kill viruses without harming body tissues?
Click “Check Mark Scheme” to compare your answer, Because viruses reproduce inside the body's own cells, so it is hard to destroy the virus without damaging the host cell.
Common Exam Questions (4)
What is a pathogen?
A pathogen is a microorganism that causes communicable disease in plants or animals, belonging to one of four groups: bacteria, viruses, fungi, or protists.
How do white blood cells defend against pathogens?
White blood cells defend against pathogens in three ways: engulfing and digesting them using enzymes (phagocytosis), producing specific complementary antibodies that bind to antigens on the pathogen, and secreting antitoxins that neutralise bacterial toxins.
What is in a vaccine?
A vaccine contains a small quantity of a dead, weakened, or inactive form of a pathogen (or its surface antigens) that stimulates white blood cells to produce specific antibodies and memory cells without causing the disease itself.
What is herd immunity?
Herd immunity occurs when a sufficiently large proportion of a population is vaccinated against a communicable disease, reducing transmission so that even unvaccinated individuals are protected from outbreaks.
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