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Pathogens and Infections

Infections are caused whenever a foreign pathogen invades an organism (animal or plant). There are four main types of pathogen:

Viruses

Viruses

  • Viruses are tiny, non-living (do not contain cells) particles that can reproduce rapidly within the body.
  • They invade host cells and use them to make new virus particles.
  • Once the new viruses are made, they cause the cells to burst.
  • The cell damage makes us feel ill.
Bacteria

Bacteria

  • Bacteria are small living cells that either damage cells directly or by producing toxins (poisons).
  • Bacteria can reproduce rapidly in the appropriate conditions: warm, moist areas with a good supply of oxygen.
  • The toxins released by bacteria can damage cells and tissues, making us feel ill.
Fungi

Fungi

  • Some fungi are single-celled organisms that have a body made up of hyphae (thread-like structures).
  • The hyphae are able to grow and penetrate tissues, such as human skin or the surface of plants.
  • The hyphae produce spores that can spread to other plants and animals.
Protists

Protists

  • Protists are single-celled eukaryotic organisms (they have a nucleus).
  • Many are parasites, meaning that they live on or inside other organisms.
  • They are often transferred to the host organism by a vector, such as an insect or mosquito.
  • They make us feel ill by damaging our tissues.
Jump to other topics
1

Cell Biology

1.1

What's in Cells?

1.2

Cell Division

1.3

Transport in Cells

2

Organisation

2.1

Principles of Organisation

2.2

Enzymes

2.3

Circulatory System

2.4

Non-Communicable Diseases

2.5

Plant Tissues, Organs & Systems

3

Infection & Response

4

Bioenergetics

5

Homeostasis & Response

5.1

Homeostasis

5.2

The Human Nervous System

5.3

Hormonal Coordination in Humans

5.4

Plant Hormones

6

Inheritance, Variation & Evolution

6.1

Reproduction

6.2

Variation & Evolution

6.3

Genetics & Evolution

6.4

Classification

7

Ecology

7.1

Adaptations & Interdependence

7.2

Organisation of Ecosystems

7.3

Biodiversity

7.4

Trophic Levels

7.5

Food Production

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