pathogens

Question 1

what are pathogens and the types of pathogens?

Answer 1

-any communicable disease-causing agent
1. non-cellular pathogens like viruses & prions
2. cellular pathogens like bacteria, protists, fungi and parasites.

Question 2

what are viruses?

Answer 2

• not true cells, do not have a plasma membrane, only a protein coat surrounds them.
• contain DNA or RNA, they are unable to replicate on their own.
• to replicate, they inject their own nucleic acids into the host cell. the host cell then uses the viral DNA or RNA to build new viruses.
• all viruses are pathogens and cause disease, each type of virus usually infects only one type of host.
• difficult to fight with medication because they hide inside the host’s cells, they are very difficult to destroy without damaging the host’s cells. however, the body’s natural immune system successfully fights viruses.
• antibiotics have no effect on viruses, vaccines prevent many viral infections
• eg, influenza, chicken pox, HIV, hepatitis B
  life cycle:
  1. virus attaches to host cell and injects DNA
  2. viral DNA integrates with the host DNA
  3. host cell replicates viral DNA and synthesises viral proteins
  4. host cell produces new viruses from viral proteins
  5. host cell dies and releases new viruses.

Question 3

what are prions?

Answer 3

• type of pathogen that does not contain any form of DNA or RNA.
• infectious molecules that have an abnormal secondary structure.
• cause a group of diseases that damage brain and nerve tissue. when infected by a prion, the infectious form of the protein can change normal proteins into the infectious form.
• prion diseases can spread between different species. e.g, people who eat beef contaminated with BSE can catch the disease.
• e.g, scrapie in sheep, kuru disease, Creutzfeldt-Jakob disease in humans, bovine spongiform encephalopathy (BSE) in cows.

Question 4

what are bacteria?

Answer 4

• prokaryotic organisms that live in most environments on earth. only a few types can cause disease, many are important for our health and survival.
• once inside the host, pathogenic bacteria reproduce very quickly by binary fission. the bacteria can break down host tissue directly. they can also produce toxins as a waste product of their metabolism. these toxins can spread throughout the host organism and poison cells.
  -e.g, streptococcus pneumonia are spherical -shaped bacteria that group together in short chains. this causes pneumonia.

Question 5

what are protists?

Answer 5

• large group of single celled eukaryotic organisms, include protozoa, unicellular algae and slime moulds. very few protists are pathogens.
• limited vaccines and treatments for the diseases they cause.
• protozoa cause most protist diseases in humans. these pathogens often move through a complex life cycle that involves different host species at different stages of development, before ending up as human parasites.
• e.g (protozoan diseases), sleeping sickness caused by Trypanosoma and is passed to humans in the bite of a tsetse fly, diarrhoea caused by many pathogens including Giardia, spread by water contaminated with faeces, malaria caused by plasmodium and is spread by mosquitoes.

Question 6

what are antibiotics?

Answer 6

• group of medicines that target bacteria, help the body’s natural immune system to fight bacterial infections.
• antibiotics that affect a wide range of bacteria are called broad spectrum
• antibiotics that target a few types of bacteria are called narrow spectrum
• different antibiotics work in different ways
  1. penicillin destroy bacterial cell walls that are made from peptidoglycan
  2. erythromycin, inhibits protein synthesis in some types of bacteria.
• e.g of bacterial infections, pneumonia, food poisoning, bubonic plague

Question 6

what are fungi?

Answer 6

• eukaryotic and can be unicellular and multicellular.
• only some fungi species are pathogens, infects a wide range of different hosts, including plants and animals
• moulds, mushrooms, toadstools and yeasts
• fungi secrete digestive enzymes onto the host. then they absorb the digested nutrients from the host through their own cellular membranes. fungal diseases are typically highly contagious.
• e.g, ringworm, thrush caused by candida, athlete’s foot.
• antibiotics have no effect on fungi

Question 6

what are parasites?

Answer 6

• any organism that completes some or all of its life on or inside another organism
• many have life stages and infected different hosts at different stages.
• developing parasites infect intermediate hosts. the host infected by a fully-developed, adult parasite is called the primary host or definitive host.
• a particular parasite may have many intermediate hosts, but only one definitive host. vectors are usually intermediate hosts of parasites, help transmit parasites between different hosts.
• endoparasites; live inside the host, e.g, tapeworm, heartworm, hookworm
• ectoparasites; live outside the host, e.g, ticks, fleas, lice.
• antibiotics have no effects on parasites
• successful treatment of parasitic diseases relies heavily on the correct identification of the parasite.