The Immune System : Infectious Diseases

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The Immune system: Infectious diseases

For a human to be considered healthy, they are said to be free from disease, and able to perform normal everyday tasks. The definition of health also takes into consideration the mental and physical state and also the social wellbeing of a person. The human body provides microorganisms with the perfect living environment, most cause us no harm and can even be of use for example friendly bacteria within the stomach, however others can cause disease. These micro-organisms that cause disease are known as pathogens. There are a wide range of pathogens that cause disease, see (Table 1) comparing the various structures, characteristics and examples of disease caused by types of protozoa, fungi, bacteria and viruses.

Table 1:
Organisms Structure and Characteristics Examples of disease caused.

Protozoa • Unicellular micro-organisms that contain a nucleus (eukaryotic).
• They usually cause damage by entering the cell and feeding on the content. • Amoeboid dysentery
• Malaria.

• Multicellular organism constructed from eukaryotic cells.
• Many fungi are saprophytes (meaning they obtain their nutrients from dead organic matter) however some are parasitic.
• They don’t contain chlorophyll therefore are unable to photosynthesise.
• They have a cell wall that contains a polysaccharide called chitin, this is only found in fungi (other cell walls
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