Communicable Diseases & Pathogens

  • Communicable Diseases can spread between organisms either of same species or sometimes between different species.

    • They spread by pathogens.

  • Pathogens are microorganisms which can cause a disease.

    • Organisms the pathogens infects is called the host

  • There are four types of pathogens:

  1. Bacteria

  2. Viruses

  3. Fungi

  4. Protoctista (Protista)

Bacteria

  • Prokaryotic cells

  • The genetic material is not found in a membrane-bound nucleus

    • Bacterial chromosome and plasmids are found in the cytoplasm

  • Bacterial cells are surrounded by a cell wall contains the chemical peptidoglycan

  • Pathogenic bacteria release toxins once they enter the body

    • Toxins are chemicals that damage host cells and tissues leading to the symptoms of the disease.

    • Some bacteria can enter host cells and prevent them functioning normally.

      • Bacteria which cause tuberculosis

Viruses

  • Smaller then bacteria

  • Non-living

  • No cellular structure

  • Consist of genetic material (DNA or RNA)

    • Wrapped in a protein structure called capsid

  • Have attachment proteins which allow the virus to attach to host cells.

  • Virus can not reproduce outside of host cells.

    • To reproduce the virus attaches to the host cell and passes through the cell membrane.

    • The virus then copies itself using the enzymes of the host cell.

    • The virus particles now leave the host cell and go on to infect new host cells and continue reproducing.

  • Viruses prevent a host cell from functioning normally.

  • Viruses can lead to the death of the host cell.

Fungi

  • Eukaryotic organisms

  • Can be unicellular or multicellular

  • Fungi obtain nutrients by relating enzymes and digestion the material around them.

    • The product of these dimensions are then absorbed into the fungal cells.

      • This process can cause damage to host cells and tissues.

  • When they reproduce, fungi release a large number of spore so fungal diseases can spread very widely.

  • In plants

    • By damaging the leaves fungi can reduce the rate of photosynthesis.

    • This reduces the yield of plant crops

Protoctista

  • Eukaryotic organisms

  • Giardia causes diarrhoea

    • Transmitted when humans drink water r contains infected faeces

  • Plasmodium is the pathogen that causes malaria in humans

    • Transmitted between humans by mosquitoes