MICR 221 MIDTERM TEST QUESTIONS
WITH ANSWERS ALL UPDATED!
What are trace elements? - Answer-very little in media since they are present in
sufficient amounts as contaminants of the major things being added to the media,
cofactors for key enzymes, copper, cobalt, manganese, zinc, nickel
How is the requirement for carbon, oxygen and hydrogen met? - Answer-add a single
organic compound like glucose or protein
What carbon source do autotrophs use; heterotrophs? - Answer-carbon dioxide;
reduced, preformed organic molecules
What energy sources do phototrophs and chemotrophs use? - Answer-light; oxidation of
organic or inorganic compounds
What hydrogen or electron sources do lithographs and organotrophs use? - Answer-
reduced inorganic molecules like hydrogen gas; organic molecules
What are the 5 nutritional types? - Answer-photolithotrophic autotrophs,
photoorganotrophic heterotrophs, chemolithotrophic autotrophs, chemoorganotrophic
heterotrophs, chemolithotrophic heterotrophs
What nutritional types are pathogens? - Answer-chemoorganotrophic heterotrophs
What are the 4 phases of cell growth? - Answer-lag, log, stationary, death
What is a batch culture? - Answer-inoculate flask of media, put in shaker, let it grow
without adding or removing anything and watch the nutrients deplete and waste grow
What is the lag phase? - Answer-the sample is inoculated into fresh media and the cell
number and mass doesn't increase. The cell is synthesizing new components.
What is the log phase? - Answer-Cells are exponentially growing at their maximal rate
possible in the media and growth conditions. Culture is uniform in chemical and
physiological properties. This phase doesn't last very long since the nutrients are
limited.
What is stationary growth? - Answer-The population growth ceases and growth curve
plateaus since nutrients are limited and there is waste buildup
What is the death phase? - Answer-Some cells will lyse and others won't due to the
buildup of toxins and nutrient deprivation from energy starvation. The curve is usually
logarithmic but can change depending on lysing
,What does doubling time depend on; how long does it last; how can it be measured? -
Answer-the media it grows in and the organism; short as 10 min to days to years;
directly from a growth curve plated on semi-log paper
What is the Petroff-Hausser Counting Chamber; difference between living and dead
cells - Answer-It uses a specially designed slide with a known depth and etched grid on
the bottom that uses a sample to count the bacteria on the grid and use a formula to
calculate the size of the original sample; they are not distinguished which affects the
growth curve and how it looks
Why does the death phase look different depending on if the cell lysed or died? -
Answer-if cells lyse, the curve will plateau and plummet. If cells die, the plateau will
continue and there is no border between the stationary and death phases
How is the cell mass measured; what if too few cells; what if too many cells? - Answer-
Measure the turbidity with a spectrophotometer; most of the light passes through and
very little is absorbed and deflected; less light is detected and light is absorbed more
How are cells grown in nature? - Answer-They are usually grown in starvation
conditions and rarely as pure cultures
What is a macroaerophile? - Answer-requires oxygen levels below 2-10% for growth
and is damaged by atmospheric oxygen levels (20%)
What is a psychrophile? - Answer-grows well at 0 C and has an optimum growth
temperature of 15 C or lower.
What is a psychrotroph? - Answer-grows at 0-7 C and has an optimum between 20-30
C and a maximum temp of 35 C
What is a facultative anaerobe? - Answer-doesn't require oxygen for growth but grows
better in its presence
What is a piezophile? - Answer-rapid growth at high hydrostatic pressures
What is a hyperthermophile? - Answer-has an optimum between 80-113 C
What does the gram negative envelope look like? - Answer-It has a cytoplasmic
membrane inside the cell and the outer membrane is chemically distinct. There is a thin
layer of peptidoglycan between the two membranes that maintains the cell shape. The
S layers and capsules are located outside.
Example of Infectious Disease in 1813 and now - Answer-1813: Napoleon's army in
Leipzig had 220,000 out of 500,000 infected with illness like typhus and dysentery which
led to his defeat
, Now: Haiti is in its 6th year of cholera that killed 10,000 and sickened 650,000
Who is Anton van Leeuwenhoek (1632-1723) and what is he credited for? - Answer-is a
haberdasher who is the first to describe microbes using microscopes that could magnify
50-300x; discovered spermatozoa and red blood cells; wee animacules
What's the conflict with Anton and Robert Hooke? - Answer-Hooke might have been
overlooked since he was the first to draw and publish a microorganism but Anton was
the first to see it. Anton was Dutch and only spoke and wrote in Dutch which no one
understood so his discoveries went unnoticed until his work was translated
Describe Anton's Microscopes - Answer-he never shared his lenses and he ground
them on his own. you hold the microscope up to your eye and let the light come through
so you could examine it
What is Spontaneous Generation? - Answer-living organisms could develop from
nonliving matter
What did Aristotle and Helmont think of spontaneous generation? - Answer-A: thought
that simple invertebrates like toads or snakes could arise from putrid water
H: placed dirty rages with cheese in the middle and mice will arise
Describe Redi's experiments - Answer-placed meat on 3 containers: one uncovered,
one covered with cork, and one covered with a fine gauze
1st one: flies laid eggs on uncooked meat and produced maggots
2nd one: no maggots on meat
3rd: flies landed on gauze and laid eggs = maggots
Result: generation of maggots on meat was by fly eggs
Describe Spallanzani's experiments - Answer-had sealed glass flasks containing beef
broth boiled for an hour and he sealed it to make it sterile. As long as the flasks were
sealed, no growth took place. He proposed that the air carried germs to culture medium
but the external air might be required for growth of animals already in the medium
Describe Pouchet's experiments - Answer-claimed to carry out experiments proving that
microbial growth could occur without air contamination
Describe Pasteur's cotton experiment - Answer-filtered air through cotton and found that
objects resembling plant spores were trapped and when he placed the cotton in a sterile
medium, microbial growth occurred
Describe Pasteur's beef broth experiment - Answer-placed nutrient solutions in flasks
and heated their necks and drew them out into a variety of curves while keeping the
ends of the necks open to air. no growth occurred even though the flasks were exposed
to air because the dust and germs were trapped on the curved necks. but if the swan
neck was broken, air could get in along with dust particles and the flask was not sterile.
WITH ANSWERS ALL UPDATED!
What are trace elements? - Answer-very little in media since they are present in
sufficient amounts as contaminants of the major things being added to the media,
cofactors for key enzymes, copper, cobalt, manganese, zinc, nickel
How is the requirement for carbon, oxygen and hydrogen met? - Answer-add a single
organic compound like glucose or protein
What carbon source do autotrophs use; heterotrophs? - Answer-carbon dioxide;
reduced, preformed organic molecules
What energy sources do phototrophs and chemotrophs use? - Answer-light; oxidation of
organic or inorganic compounds
What hydrogen or electron sources do lithographs and organotrophs use? - Answer-
reduced inorganic molecules like hydrogen gas; organic molecules
What are the 5 nutritional types? - Answer-photolithotrophic autotrophs,
photoorganotrophic heterotrophs, chemolithotrophic autotrophs, chemoorganotrophic
heterotrophs, chemolithotrophic heterotrophs
What nutritional types are pathogens? - Answer-chemoorganotrophic heterotrophs
What are the 4 phases of cell growth? - Answer-lag, log, stationary, death
What is a batch culture? - Answer-inoculate flask of media, put in shaker, let it grow
without adding or removing anything and watch the nutrients deplete and waste grow
What is the lag phase? - Answer-the sample is inoculated into fresh media and the cell
number and mass doesn't increase. The cell is synthesizing new components.
What is the log phase? - Answer-Cells are exponentially growing at their maximal rate
possible in the media and growth conditions. Culture is uniform in chemical and
physiological properties. This phase doesn't last very long since the nutrients are
limited.
What is stationary growth? - Answer-The population growth ceases and growth curve
plateaus since nutrients are limited and there is waste buildup
What is the death phase? - Answer-Some cells will lyse and others won't due to the
buildup of toxins and nutrient deprivation from energy starvation. The curve is usually
logarithmic but can change depending on lysing
,What does doubling time depend on; how long does it last; how can it be measured? -
Answer-the media it grows in and the organism; short as 10 min to days to years;
directly from a growth curve plated on semi-log paper
What is the Petroff-Hausser Counting Chamber; difference between living and dead
cells - Answer-It uses a specially designed slide with a known depth and etched grid on
the bottom that uses a sample to count the bacteria on the grid and use a formula to
calculate the size of the original sample; they are not distinguished which affects the
growth curve and how it looks
Why does the death phase look different depending on if the cell lysed or died? -
Answer-if cells lyse, the curve will plateau and plummet. If cells die, the plateau will
continue and there is no border between the stationary and death phases
How is the cell mass measured; what if too few cells; what if too many cells? - Answer-
Measure the turbidity with a spectrophotometer; most of the light passes through and
very little is absorbed and deflected; less light is detected and light is absorbed more
How are cells grown in nature? - Answer-They are usually grown in starvation
conditions and rarely as pure cultures
What is a macroaerophile? - Answer-requires oxygen levels below 2-10% for growth
and is damaged by atmospheric oxygen levels (20%)
What is a psychrophile? - Answer-grows well at 0 C and has an optimum growth
temperature of 15 C or lower.
What is a psychrotroph? - Answer-grows at 0-7 C and has an optimum between 20-30
C and a maximum temp of 35 C
What is a facultative anaerobe? - Answer-doesn't require oxygen for growth but grows
better in its presence
What is a piezophile? - Answer-rapid growth at high hydrostatic pressures
What is a hyperthermophile? - Answer-has an optimum between 80-113 C
What does the gram negative envelope look like? - Answer-It has a cytoplasmic
membrane inside the cell and the outer membrane is chemically distinct. There is a thin
layer of peptidoglycan between the two membranes that maintains the cell shape. The
S layers and capsules are located outside.
Example of Infectious Disease in 1813 and now - Answer-1813: Napoleon's army in
Leipzig had 220,000 out of 500,000 infected with illness like typhus and dysentery which
led to his defeat
, Now: Haiti is in its 6th year of cholera that killed 10,000 and sickened 650,000
Who is Anton van Leeuwenhoek (1632-1723) and what is he credited for? - Answer-is a
haberdasher who is the first to describe microbes using microscopes that could magnify
50-300x; discovered spermatozoa and red blood cells; wee animacules
What's the conflict with Anton and Robert Hooke? - Answer-Hooke might have been
overlooked since he was the first to draw and publish a microorganism but Anton was
the first to see it. Anton was Dutch and only spoke and wrote in Dutch which no one
understood so his discoveries went unnoticed until his work was translated
Describe Anton's Microscopes - Answer-he never shared his lenses and he ground
them on his own. you hold the microscope up to your eye and let the light come through
so you could examine it
What is Spontaneous Generation? - Answer-living organisms could develop from
nonliving matter
What did Aristotle and Helmont think of spontaneous generation? - Answer-A: thought
that simple invertebrates like toads or snakes could arise from putrid water
H: placed dirty rages with cheese in the middle and mice will arise
Describe Redi's experiments - Answer-placed meat on 3 containers: one uncovered,
one covered with cork, and one covered with a fine gauze
1st one: flies laid eggs on uncooked meat and produced maggots
2nd one: no maggots on meat
3rd: flies landed on gauze and laid eggs = maggots
Result: generation of maggots on meat was by fly eggs
Describe Spallanzani's experiments - Answer-had sealed glass flasks containing beef
broth boiled for an hour and he sealed it to make it sterile. As long as the flasks were
sealed, no growth took place. He proposed that the air carried germs to culture medium
but the external air might be required for growth of animals already in the medium
Describe Pouchet's experiments - Answer-claimed to carry out experiments proving that
microbial growth could occur without air contamination
Describe Pasteur's cotton experiment - Answer-filtered air through cotton and found that
objects resembling plant spores were trapped and when he placed the cotton in a sterile
medium, microbial growth occurred
Describe Pasteur's beef broth experiment - Answer-placed nutrient solutions in flasks
and heated their necks and drew them out into a variety of curves while keeping the
ends of the necks open to air. no growth occurred even though the flasks were exposed
to air because the dust and germs were trapped on the curved necks. but if the swan
neck was broken, air could get in along with dust particles and the flask was not sterile.
