pathogens and disease 3.1.1

• a communicable disease is one that can be passed from one person to another and is caused by pathogens
• a non-communicable disease is one that cannot be passed from one person to another and is not caused by pathogens
• a microorganism is a small single celled organism that cannot be seen seen with the naked eye, only by using a microscope
• a pathogen is a microorganism that causes a disease (communicable) and both plants and animals can be infected by pathogens
• health is a state of physical and mental well-being and an absence of disease
• examples of bacteria microorganisms are tuberculosis, cholera, food poisoning and impetigo
• examples of virus microorganisms are measles, chickenpox, aids, the common cold and covid
• examples of fungi microorganisms are athletes foot
• examples of protoctista microorganism is malaria
• however, not all microorganisms are bad for you for example, useful bacteria can be used to make cheese and yoghurt and treat sewage and useful fungi can be used to make bread, alcohol, penicillins and even microproteins
• bacteria key features are they have no nucleus, may have plasmid dna, reproduce by binary fission and are much smaller than animal and plant cells
• bacteria cause disease by releasing toxins, rapidly dividing and living in vascular tissue in plants causing blackening and death of these tissues
• some fungi are single celled for example yeast, whereas other fungi are multi-cellular and form thread like structures called hyphae which grow and penetrate human skin and the surface of plants, causing diseases
• fungi cause disease by feeding on cells which causes damage to the tissues they infect and some fungi may also release toxins
• viruses are even smaller than bacteria and the dna is encased in a protein coat, they need a host cell to reproduce and that aren’t considered alive as they don’t perform most of the MRS GREN living processes
• viruses cause diseased by infecting and taking over host cells, they cause the cell to make copies of the virus and these cells then release these virus particles and in process are either killed or damaged
• protoctista are a diverse group of organisms that are eukaryotic, many are unicellular organisms but included algae, seaweeds and phytoplankto, some photosynthesise while others capture food or are decomposers
• protoctista cause disease by entering host cells and feeding on them as they grow and reproduce
• pathogens can be :

  • bacteria
  • viruses
  • protists
  • fungi