MIMG 101 Midterm 1 Study Guide
Exam with All Correct Answers 2026
Updated.
Antoni van Leewenhoek - Answer • Dutch amateur microscope builder
• Observed "animalcules" (microscopic animals)
Lazzaro Spallanzani - Answer • Experiment to test where microbes come from: "spontaneous
generation" (life arose from inanimate chemicals) or "life from life" (microbes are already
present in air)
• experiment: heated a test tube then added stopper -> found that there was no growth ->
supported spontaneous generation
• criticisms:
o Heating destroys life-generating substances
o Oxygen may be necessary for "spontaneous generation"
Louis Pasteur - Answer • Disproved spontaneous generation by refuting criticisms
• His experiment showed that spontaneous generation does not occur and that organisms
found were present in the air
• discovered that fermentation is a microbial process (wine industry)
Robert Koch - Answer • proved germ theory of disease (some diseases are caused by
microbes that may be present in air, water, or food, and may be passed from one diseased
individual to another)
Koch's Postulates - Answer • the procedure for defining the agent of any disease
o pathogen should be in diseased animals and not in healthy ones
o "The suspected organism should be grown in pure culture."
o causes disease in healthy animal
o "The organism should be re-isolated and shown to be the same as the original."
Is shape a good indicator of a bacteria's identity? - Answer Yes, but it is not a certain
indicator; need further diagnosis
Light microscope - Answer • compound microscope - uses >= 2 lenses
o ocular (10x) & objective lens
o to calculate magnification: multiply ocular by objective
,• types: bright-field, dark-field, phase-contrast, fluorescence, confocal
refraction - Answer • bending of light through a medium to slow down light so it doesn't
scatter everywhere
• what let's lens magnify an image
dark-field microscopy - Answer • Light image on dark background, light reaches specimen
from the sides, and only scattered light reaches the lens
phase-contrast microscopy - Answer • uses brightness variations when light passes through
specimen to show high contrast, detailed image of unstained cells
• Provides better detail of structures and can be performed on live cells without staining
Differential Interference Contrast microscopy (DIC) - Answer • uses sections to create 3D
appearance
• best way to observe living cells: Can see (larger) internal structure of unstained cells
fluorescence microscopy - Answer • stain specimen with fluorochromes then shine
ultraviolet, violet, or blue light on it to show fluorochrome color in image
• good for tracking gene expression over long period of time
Confocal Scanning Laser Microscopy (CSLM) - Answer • uses laser to chop up image and
recreate it
electron microscope - Answer • Much more powerful than light microscopy (1000x better
resolution)
• Have to have dead cells, uses electrons rather than light
Transmission Electron Microscope (TEM) - Answer • Thinly sectioned samples treated with
specialized stains, internal structures detected with high resolving power
Scanning Electron Microscope (SEM) - Answer • Fix the sample, treat with a heavy metal,
used for high resolution of external structures
gram stain - Answer 1. crystal violet dye is added
2. mordant (iodine) is added to form complex between violet dye and teichoic acid in
peptidoglycan
3. add decolorizer (alcohol) to wash out violet dye
, 4. add safranin (pink dye)
• purple cells = gram positive (has teichoic acid)
• red cells = gram negative
acid-fast stain - Answer • identifies gram-positive bacteria with mycolic acid in cell wall (are
hard to stain)
endospore stain - Answer • green cell = endospore (dormant cell that cannot grow or
reproduce but can survive in harsh conditions)
• red cell = vegetative (active cell that can reproduce)
capsule stain - Answer • clear = bacterial capsule (stain can't get into capsule)
• good for making biofilms
flagellar stain - Answer • purple = bacterial flagella
1. mordant
2. crystal violet dye
Chemotaxis - Answer stimulate movement through chemicals (ex: acidic or basic
environment)
phototaxis - Answer stimulate movement through chemicals (ex: acidic or basic environment)
monotrichous flagella - Answer one flagellum at one end
lophotrichous flagella - Answer multiple flagella at one end
amphitrichous flagella - Answer flagella at both ends of cell
petrichous flagella - Answer flagella all over the cell
Pili - Answer • long microfibers on bacteria surface that is more efficient for transporting
plasmids & other molecules
• difference from flagella: is a protein
Plasmid - Answer • small DNA molecule in bacteria
Exam with All Correct Answers 2026
Updated.
Antoni van Leewenhoek - Answer • Dutch amateur microscope builder
• Observed "animalcules" (microscopic animals)
Lazzaro Spallanzani - Answer • Experiment to test where microbes come from: "spontaneous
generation" (life arose from inanimate chemicals) or "life from life" (microbes are already
present in air)
• experiment: heated a test tube then added stopper -> found that there was no growth ->
supported spontaneous generation
• criticisms:
o Heating destroys life-generating substances
o Oxygen may be necessary for "spontaneous generation"
Louis Pasteur - Answer • Disproved spontaneous generation by refuting criticisms
• His experiment showed that spontaneous generation does not occur and that organisms
found were present in the air
• discovered that fermentation is a microbial process (wine industry)
Robert Koch - Answer • proved germ theory of disease (some diseases are caused by
microbes that may be present in air, water, or food, and may be passed from one diseased
individual to another)
Koch's Postulates - Answer • the procedure for defining the agent of any disease
o pathogen should be in diseased animals and not in healthy ones
o "The suspected organism should be grown in pure culture."
o causes disease in healthy animal
o "The organism should be re-isolated and shown to be the same as the original."
Is shape a good indicator of a bacteria's identity? - Answer Yes, but it is not a certain
indicator; need further diagnosis
Light microscope - Answer • compound microscope - uses >= 2 lenses
o ocular (10x) & objective lens
o to calculate magnification: multiply ocular by objective
,• types: bright-field, dark-field, phase-contrast, fluorescence, confocal
refraction - Answer • bending of light through a medium to slow down light so it doesn't
scatter everywhere
• what let's lens magnify an image
dark-field microscopy - Answer • Light image on dark background, light reaches specimen
from the sides, and only scattered light reaches the lens
phase-contrast microscopy - Answer • uses brightness variations when light passes through
specimen to show high contrast, detailed image of unstained cells
• Provides better detail of structures and can be performed on live cells without staining
Differential Interference Contrast microscopy (DIC) - Answer • uses sections to create 3D
appearance
• best way to observe living cells: Can see (larger) internal structure of unstained cells
fluorescence microscopy - Answer • stain specimen with fluorochromes then shine
ultraviolet, violet, or blue light on it to show fluorochrome color in image
• good for tracking gene expression over long period of time
Confocal Scanning Laser Microscopy (CSLM) - Answer • uses laser to chop up image and
recreate it
electron microscope - Answer • Much more powerful than light microscopy (1000x better
resolution)
• Have to have dead cells, uses electrons rather than light
Transmission Electron Microscope (TEM) - Answer • Thinly sectioned samples treated with
specialized stains, internal structures detected with high resolving power
Scanning Electron Microscope (SEM) - Answer • Fix the sample, treat with a heavy metal,
used for high resolution of external structures
gram stain - Answer 1. crystal violet dye is added
2. mordant (iodine) is added to form complex between violet dye and teichoic acid in
peptidoglycan
3. add decolorizer (alcohol) to wash out violet dye
, 4. add safranin (pink dye)
• purple cells = gram positive (has teichoic acid)
• red cells = gram negative
acid-fast stain - Answer • identifies gram-positive bacteria with mycolic acid in cell wall (are
hard to stain)
endospore stain - Answer • green cell = endospore (dormant cell that cannot grow or
reproduce but can survive in harsh conditions)
• red cell = vegetative (active cell that can reproduce)
capsule stain - Answer • clear = bacterial capsule (stain can't get into capsule)
• good for making biofilms
flagellar stain - Answer • purple = bacterial flagella
1. mordant
2. crystal violet dye
Chemotaxis - Answer stimulate movement through chemicals (ex: acidic or basic
environment)
phototaxis - Answer stimulate movement through chemicals (ex: acidic or basic environment)
monotrichous flagella - Answer one flagellum at one end
lophotrichous flagella - Answer multiple flagella at one end
amphitrichous flagella - Answer flagella at both ends of cell
petrichous flagella - Answer flagella all over the cell
Pili - Answer • long microfibers on bacteria surface that is more efficient for transporting
plasmids & other molecules
• difference from flagella: is a protein
Plasmid - Answer • small DNA molecule in bacteria
