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Cells-2-Pathogenic-Microbes Powered By Docstoc
					                        MCD – Cells 2 – Pathogenic Microbes
Anil Chopra

   1.  Name the main types of infectious agent causing disease in humans
   2.  List the key differences between prokaryotes and eukaryotes
   3.  Give examples of each type of infectious agent and the disease it causes
   4.  Name the distinguishing features of the different types of infectious agent and
       explain how they replicate
Type            Example                   Features
Bacteria        Mycobacterium             Prokaryotes that replicated by binary fission, they
                tuberculosis, E. coli,    contain chromosomes, but no nucleus. Their DNA
                Neisseria meningitides is circular. They inhabit the gut, skin, they stimulate
                                          the immune system and aid with metabolism and
                                          provision of nutrients. Some are pathogenic and can
                                          in the immuno-compromised, cause infections
                                          (opportunistic infections).
Viruses         HIV, common cold,         Not cells in their own right (obligate parasites),
                influenza                 inhibit host cell from replicating. Contain DNA or
                                          RNA and use reverse transcriptase to divide. Make
                                          use of a host cell nuclear synthetic machinery to
                                          replicate and divide by budding out of the host cell.
                                          Show host specificity but infect almost all other life
                                          forms including bacteria.
Fungi           Candida albicans          Single celled eukaryotes that exist as yeasts or
                (thrush), aspergillus     filaments. Yeasts bud or divide; filaments (hyphae)
                fumigatus                 which have cross walls or septa.Usually affect
                                          immuno-compromised people. Causes mycoses
Protozoa        Malaria, leishmaniasis     Single celled eukaryotes, include intestinal, blood
                                           and tissue parasites. Replicate in host by binary
                                           fission or by forming trophozoites in a cell. Many
                                           have complicated life cycle involving 2 hosts.
                                           Infection acquired by ingestion or via a vector.

Helminths       Tapeworm, fluke,           Multicellular organisms. Have life cycles outside
                roundworms                 human host, visible to the naked eye. Complex life
                                           cycle including embronation to generations in
                                           different hosts.