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Microbial Physiology Exam 2 - Chapter 14
Terms in this set (35)
plant roots form nodules when bacteria convert nitrogen to ammonia
plants depend on the amount of nitrogen in the soil
What organisms perform nitrogen fixation?
What is the bacterial product of N fixation? What product is transferred to plants?
Nodules convert nitrogen to ammonia. Bacteria assimilate the ammonia into the amino acid alanine.
How is the bacterial product of N fixation transferred to plants?
Ammonia is first transferred to plants by first being incorporated into ALANINE with the help of ALANINE DEHYDROGENASE, which is then released to the plant.
What are two sources of energy for N cycle?
Hydrogen gas serves as a source of energy because it consumes oxygen gas.
C4 TCA Cycle Intermediates are used to oxidize and form ATP.
enzyme unique to bacteria and it enables the fixation of nitrogen
contains 2 oxygen sensitive proteins
*Component I - dinitrogenase
*Component II - dinitrogenase reductase
(transfer e- to Component I)
What type of environment is essential for nitrogenase activity?
Anaerobic because of the liability of both protein components. Nitrogenase contains several iron atoms that could become disrupted if it were to become oxidized by any oxygen gas.
How many electrons are required for nitrogenase activity?
How many ATP are required for nitrogenase activity?
What are two levels of regulation for nitrogen fixation?
Transcriptional & Covalent Modification
Glutamine requires ammonia for synthesis thus controlling the system
Ammonia can inactivate nitrogenase
exchange signal between plant and bacteria
ex: plants need nitrogen and bacteria need a nice home, food and oxygen
What is an example of symbiosis between plants and bacteria?
(1) Plants secrete flavonoids, which induce Nod D genes in bacteria.
(2) Nod D genes become activated.
(3) One set of nod genes synthesize lipopolysaccharides which trigger hair curl
What are exopolysaccharides?
They are bacterial polysaccharides synthesized and secreted into the external environment or are synthesized extracellular by cell wall-anchored enzymes.
What is host bacterial specificity?
When the invasion of a root nodule is dependent on at least one of several complex polysaccharides.
What is the result of denitrification?
Nitrate to nitrogen
During denitrification, nitrate can act as two things. What are they?
*source of nitrogen
*nitrate as an electron acceptor
*membrane-bound nitrate reductase
*nitrate as a source of nitrogen
*cytoplasmic nitrate reductase
E. coli is the only organism that contains two different nitrate reductases. What are they?
*Respiratory Enzyme (membrane-bound nitrogen reductase)
*Assimilatory Enzyme (cytoplasmic nitrogen reductase)
The pathways for ammonia assimilation includes two major enzymes. What are they?
*Glutamate dehdrogenase (GDH)
*Glutamine synthase (GS)-glutamate synthase (GOGAT)
When is glutamate dehydrogenase used during ammonia assimilation?
It is used when ammonia is abundant.
*saves energy because no ATP is used
*low affinity for ammonia
When is glutamine synthase-glutamate synthase used during ammonia assimilation?
It is used when ammonia is scarce.
*depletes glutamate during first step, but two more glutamate are produced.
*high affinity for ammonia
Ammonia assimilation is in competition with what major cycle? Why?
TCA cycle, because alpha-ketoglutarate is being depleted.
What organisms can do ammonia assimilation?
How much energy is used for ammonia assimilation?
What coenzyme is a part of all known transaminase reactions?
What enzymes catalyze the conversion of D-amino acids to L-amino acids?
What coenzyme does racemase need?
What is the major racemase in bacteria?
Why is pyridoxal phosphate a versital compound?
It allows for enzymes to cleave bonds in three major places and its an electron sink.
What major role does pyriodoxal phosphate serve when attached as a cofactor to an enzyme?
The protein that this cofactor is attached to determines which reaction is catalyzed, since it holds the cofactor in place.
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