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MCB 301: Biochemical Tests Study Q&A’S Latest Update
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MCB 301: Biochemical Tests Study Q&A’S Latest Update
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MCB 301: Biochemical Tests Study Q&A’S LatestUpdate
Nitrate reduction test relies on production of _______________________ from nitrite
which reacts with _______________ in the reagent to produce a blue color - ✔✔-
nitrous acid
- starch
Give a variation of a nitration reduction test.
Explain how this work. (include advantage) - ✔✔-use blood agar containing nitrate
-if nitrate is produced, it reacts with hemoglobin to give a bright red color, instead of the
dark red color of hemoglobin
-test has advantage of no color change occurring if nitrite is further reduced
(Electron transport)
name membrane-associated electron carries - ✔✔flavoproteins, iron-sulfur proteins,
quinones, and cytochromes
What is the last electron carrier in anaerobic respiration?
What does it do? - ✔✔-nitrate reductase
-transfers electrons to an oxygen-containing compound other than O2 (e.g., nitrate)
by-product of oxidation-reduction in the presence of O2 during aerobic respiration? -
✔✔hydrogen peroxide-
,How is catalase test performed on y. pestis organism and why? - ✔✔y. pestis is an
infectious disease that can be spread by inhalation
-to prevent bubble release, Y. pestis is stabbed into agar containing H2O2. any bubbles
produced are trapped in agar and thier presence is determined by examining the stab
with a microscope
What is unique about hydrogen peroxide? - ✔✔-highly reactive
-must be degraded in the cytoplasm of cell producing it
-can be damaging to molecules of DNA
What does catalase do? - ✔✔-breaks down H2O2 into water and oxygen
Catalase production is GENERALLY associated with what kind of organisms? -
✔✔aerobic organisms
What is the last electron carrier in ETC?
What does it do? - ✔✔-cytochrome oxidase
-transfers electrons to terminal electron acceptor, oxygen
(nitrate reduction test) Why is a durham tube used? - ✔✔-some of the possible
products of NO3- reduction are gaseous, this tube is inverted in culture to trap gases
Nitrate reduction test:
no color after addition of zinc dust - ✔✔(+2)
nitrate was reduced to nitrite then further reduced to another compound such as NH3
, What are the 2 possible reasons for a negative reaction for a nitrate reduction test? -
✔✔1. no nitrate reduction occurred, so nitrite present
2. nitrate reduction did occur, but all nitrite was further reduced to other products, so
no nitrite is present
Why do we swirl the Trommsdorf I reagent? - ✔✔to suspend starch
what test is used to detect nitrite - ✔✔trommsdorf test
in the simmons citrate agar growth in oxic conditions will cause a change in color from
green to blue indicating an __________ reaction has taken place - ✔✔alkaline
what is the pH range from brom thymol blue? - ✔✔6.0 to 7.6
what pH indicator is used in simmons citrate agar? - ✔✔brom thymol blue (BTB)
What can urease be cleaved to? - ✔✔carbon dioxide and ammonia
(Urease) ammonia is a nitrogen source for ____________________ as well as for
______________________________ - ✔✔-amino acid biosynthesis
-synthesis of other nitrogen-containing molecules in the cell
what pathway does the VP test detect? - ✔✔butanediol fermentation pathway
what molecule acts as a terminal electron acceptor in the butanediol pathway? -
✔✔acetoin
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