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MCAT Biology Question — Pathogens

  • by John
  • Jun 24, 2017
  • MCAT Question of the Day

A child goes to the pediatrician with a sore throat. The pediatrician swabs the throat and places the swab in an acellular culture medium. No pathogens are seen in the culture, even under a light microscope. The pathogen may be a:

A. bacterium

B. fungus

C. virus

D. parasitic worm

Click for Explanation

Bacteria, fungus, and parasitic worms could all be seen under the light microscope. Viruses cannot be seen under light microscopes, and require tissue-culture or cellular growth medium in order to reproduce.

A) bacterium, incorrect, Bacteria can be seen with light microscope with a size on the order of microns.

B) fungus, incorrect, Fungus and yeast can be seen with the light microscope.

C) virus, correct, Virus particles have size on the order of nanometers making them undetectable with the light microscope.

D) parasitic worm, incorrect, Parasitic worms are eukaryotes with sizes of many microns up to centimeters in size.

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