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Micro Lab 2 exam

microbiology

QuestionAnswer
reduction a gain of electron or hydrogen atoms
why does hydrogen peroxide bubble when poured on cut skin? skin normal flora makes catalase
differentiate between aerobic and anaerobic respiration aerobic- O2 is final electron acceptor anaerobic- inorganic compounds other than O2 is final electron acceptor
Differentiate between fermentation and anaerobic respiration. Fermentation- organic compound is final electron acceptor Anaerobic respiration- inorganic compounds other than O2 are final electron acceptor
Would nitrate reduction occur more often in the presence or absence of O2? Absence because if O2 was present,it would use O2 instead of nitrogen as the final electron acceptor
In nitrate reduction test, what does the presence of gas indicate? Nitrate has been reduced to nitrate then to nitrous oxide then nitrogen gas (nitrate--->nitrite--->nitrous oxide--->nitrogen gas)
Is nitrate reduction beneficial or harmful to farmers? nitrate reduction is harmful because plants need nitrates to survive. If nitrates are reduced to NO or N2, there is less available for the plants.
In the Nitrate reduction test, why did no color change appear after adding Nitrate A & B and zinc in P. aeruginosa? The nitrates were reduced to nitrites then nitrous oxide and finally to nitrogen gas
When did E. faecalis exhibit color change in the nitrate reduction test? There was no color change after nitrate A and B were added. It turned red after zinc dust was added
What is the purpose of the Respiration Lab? To classify bacteria as aerobic or anaerobic.
what two organisms were positive for nitrate reduction? P. aeruginosa and B. subtilis
What organism was positive and what organism was negative for the oxidase test? E.coli was negative (did not have cytochrome c) P. aeruginosa was positive (contains cytochrome c)
what two organisms did we use in the catalase test? E. faicalis and B. subtilis
What organism was positive in the Catalase test? B. subtilis
The nitrate reduction test tests for what kind of organisms? anaerobes
The oxidase and catalase test test for what kind of organisms? aerobes
Why did we examine for gas production in the Nitrate reduction test? If there is gas, the nitrate was reduced to nitrogen gas.
In what order is nitrate reduced to nitrogen gas? nitrate-->nitrite-->nitrous oxide-->nitrogen gas
the chromosomal DNA of E.coli contains how many base pairs? 3,000,000
The DNA of E. coli is attached to what? plasma membrane
What is the average fragment length of the large fragments of chromosomal DNA? 100,000 to 200,000 base pairs
what is the average length of a gene? 2000 base pairs
A convenient method for analyzing DNA of e. coli that consists of microscopic pores in the gel that act as a molecular sleeve Agarose gel electrophoresis
where are the samples of DNA loaded into in the Agarose gel? wells made in the gel during casting
Why does the DNA migrate towards the positive electrode? DNA has a strong negative charge at neutral pH
How are the linear fragments of DNA separated? The pores in the gel separate the linear fragments according to their size
Why does DNA appear as a smear? If many fragments are present in a wide range of sizes it will appear as a smear (badly sheared DNA)
What is the objective of the Isolation of E.coli DNA lab? to isolate bacterial chromosomal DNA with a minimum of breaks
The resuspended e. coli cells are first mixed with what solution? EDTA
What forms complexes (chelates) with several kinds of metal ions? EDTA
what kind of divalent metal cations are required cofactors by the majority of DNases? Mg+2
what dissolves the cell membrane and denatures many proteins? sarkosyl
What degrades high molecular weight RNA? RNase
what proteolytic enzyme is added to the cell lysate in order to digest proteins that are free in solution or bound to DNA? protease
Eventually, what degrades RNase? protease
in isolation of DNA of E. coli, how many mililiters of resuspended e. coli cells are in the tube in step 1? 5ml
To break cell walls, we added 2 mls of what buffer? EDTA
how many different bacteria were in the mixed culture in isolation by dilution? 2
How many bacteria were in the turbid broth in isolation by dilution? 1
In isolation by dilution...how do colonies on the surface of the pour plates differ from those suspended in agar? because of different O2 requirements
what is a contaminate? unwanted organism
how would you tell if a colony was contaminated on a streak plate? it was in an area that was uninoculated and has different morphology
What would happen if plates were incubated a week longer? (ibd) bacteria would be overgrown
What would happen if plates were incubated a month longer? too numerous to count
How could your streak plate technique be improved? 1)spread more evenly 2) flame and cool loop
Could some bacteria grow on the streak plate but not be seen using the pour plate? depends on O2 requirements
what is a disadvantage of the streak plate too many to count
what is a disadvantage of the pour plate? hard to see isolation and solidifies too fast
What three organisms did we use in the oF-glucose test? P. aeruginosa, E. coli, and A. faecalis
Why do most bacteria catabolize carbohydrates? carbon and energy
What three sizes are carbohydrates classified as? monosaccharide, disaccharide, and polysaccharide
How do we look for the presence of an exoenzyme? by looking for a change in substrate outside of bacteria colony
What can enter a cell and be catabolized? glucose
What are the metabolic endproducts of fermentation? organic acids
What test helps determine whether an organism is oxidative or fermentative? OF Glucose
What indictor does OF glucose use? bromthymol blue
bromtymol blue turns what color in the presence of acids? yellow
Created by: brimme123