4.1. Communicable Diseases Prevention and the Immune System

What is a communicable disease?

A disease caused by a pathogen that can be transmitted between organisms

What is a pathogen?

A microorganism that causes disease

What are the four main types of pathogen?

Bacteria, viruses, fungi, protoctista

How are communicable diseases transmitted directly?

Droplet infection, direct contact, exchange of body fluids

How are communicable diseases transmitted indirectly?

Contaminated food/water, vectors, spores

What is a vector?

An organism that carries and transmits a pathogen

What is a bacterium?

A prokaryotic microorganism that can cause disease

How do bacteria cause disease?

Release toxins and damage tissues

What is a virus?

Non-living infectious particle that replicates inside host cells

How do viruses cause disease?

Invade cells and replicate, damaging or destroying cells

What is a fungus?

A eukaryotic organism that can act as a pathogen

How do fungi cause disease?

Digest and damage host tissues

What is a protoctist?

A eukaryotic microorganism, some of which are pathogenic

Give an example of a protoctist disease

Malaria

What are physical barriers to infection in humans?

Skin, mucus, cilia

What is the role of mucus?

Traps pathogens

What is the role of cilia?

Move mucus containing pathogens out of airways

What are chemical barriers to infection?

Lysozyme in tears, stomach acid

What is lysozyme?

An enzyme that breaks down bacterial cell walls

What is phagocytosis?

Engulfing and digesting pathogens by phagocytes

What are phagocytes?

White blood cells that ingest pathogens

What is an antigen?

A molecule on pathogen surface recognised as foreign

What is an antibody?

A protein produced by B cells that binds to specific antigen

What is an antigen-antibody complex?

Formed when antibody binds to antigen

What is opsonisation?

Process where pathogens are marked for destruction by phagocytes

What are T lymphocytes?

White blood cells involved in cell-mediated immunity

What are B lymphocytes?

White blood cells involved in antibody production

What is clonal selection?

Activation and replication of specific lymphocytes

What is primary immune response?

First response to pathogen → slow production of antibodies

What is secondary immune response?

Faster and stronger response due to memory cells

What are memory cells?

Long-lived cells that remember specific antigens

What is active immunity?

Immunity produced by own immune system

What is passive immunity?

Immunity gained from another organism’s antibodies

What is natural active immunity?

Immunity after infection

What is artificial active immunity?

Immunity via vaccination

What is natural passive immunity?

Antibodies passed from mother to baby

What is artificial passive immunity?

Injection of antibodies

What is vaccination?

Introduction of antigen to stimulate immune response

How do vaccines work?

Stimulate production of memory cells without causing disease

What is herd immunity?

When enough people are immune to prevent spread of disease

What are antibiotics?

Drugs that kill or inhibit bacteria

Why don’t antibiotics work on viruses?

Viruses lack cellular structures targeted by antibiotics

What is antibiotic resistance?

Bacteria evolve to survive antibiotics

What is MRSA?

A strain of bacteria resistant to multiple antibiotics

How can spread of disease be reduced?

Hygiene, vaccination, isolation, vector control

What are plant physical defences?

Waxy cuticle, bark, cell walls

What are plant chemical defences?

Toxins and antibacterial compounds

What is a plant vector?

Organism that spreads plant pathogens

How do environmental factors affect disease transmission?

Temperature, humidity, and population density influence spread