Communicable Diseases

Last updated May 26, 2023 Edit

• Biology
• Disease

• Communicable diseases are caused by one organism that infects another
• Infective organisms are known as pathogens
• Pathogens include: bacteria, viruses, protists and fungi.

• The most common organism for infection
• Not all bacteria are pathogens, most do not cause disease
• Bacteria are typically classified using their basic shape and cell wall Pasted image 20230123094409.png

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• Viruses are non-living
• Viruses are a section of RNA surrounded by a protein.
• Viruses infect cells by inserting its DNA into the host cell
• The infected cell will then begin to produce viral proteins
• All natural viruses are pathogens
• Viruses effect all types of organisms, including bacteria, those are called bacteriophages.

• Virus attaches to host cell
• Inserts viral nucleic acid
• The cell replicates viral nucleic acid
• The cell synthesises viral proteins
• assembly of virus particles
• Lysis of host cell and new bacteriophages released

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• Eukaryotic cells
• Exist as single organisms and as colonies
• A small percentage are pathogenic, they can affect animals and plants (ie, malaria)
• Often protista require a vector to transfer the disease (eg, mosquitos for malaria) Pasted image 20230123094908.png

• Not usually a large issue for animals, but affects plants massively
• Eukaryotes, can be unicellular or multicellular
• Many fungi are saprophytes, meaning they feed off of decaying matter
• When fungi infect plants, they often target the leaves, preventing photosynthesis
• Fungi produce many millions of spores that rapidly infect other organisms

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• Viruses
  • Take over cellular metabolism
  • Viral genetic material is inserted into the genetic material of the host cell
  • The host cell then produces more viruses, which burst out, destroying it.
• Protista
  • They take over a cell, digest the insides and use this as a medium to reproduce, before bursting out.
• Fungi
  • Digest and destroy living cells.

• Most pathogenic bacteria will produce a toxin, which is a poison.
• This toxin damages the cells of the host organism, often by breaking down the plasma membrane or inactivating enzymes.
• Some fungi also produce toxins

Disease