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Meharry Biochem > Nitrogen Metabolism > Flashcards

Nitrogen Metabolism Flashcards

1
Q

Can you store nitrogen

A

no

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2
Q

name 3 things that nitrogen is an important component of

A

cofactors, hormones, neurotransmitters

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3
Q

can we use the N2 that is in the atmosphere

A

no, our atmosphere is made of 80% N , but it is in a non useful form.

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4
Q

what form of Nitrogen can we use?

A

NH3, ammonia

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5
Q

Does turning atmospheric nitrogen into ammonia have high or low activation energy ?

A

Very high activation energy

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6
Q

What are some processes to turn Nitrogen into a useful form?

A

2 non biological processes are:

N2 + o2 —> NO via lightening
N2+ H2 —-> NH3 via haber process

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7
Q

What are the oxidation states of nitrogen

A

-3 and +5

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8
Q

higher oxidation state is “ate” or “ite”

A

ate

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9
Q

lower oxidation state is ate or ite

A

lower is ite

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10
Q

what are the 4 steps in the nitrogen cycle ?

A

Fixation
Nitrofication
Assimilation
Denitrification

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11
Q

what does fixation refer to

A

bacteria reducing N2 —> NH3 (ammonia) or NH4 ( ammonium)

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12
Q

what does nitrification refer to ?

A

Bacteria oxidizing NH3—-> No2- ( nitride) and N03- (nitrate

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13
Q

What is assimilation

A

plants and microorgansims reducing NO2- and NO30 to NH3 via nitrite reductase and Nitrate reductase

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14
Q

what 2 enzymes are used in assimilation

A

nitrite reductase and Nitrate reductase

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15
Q

What does denitrification refer to

A

NO3- reduced to N2 under anaerobic conditions

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16
Q

what is the ultimate electron acceptor

A

NO3-

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17
Q

Do humans do nitrogen assimilation

A

no , only plants and bacteria have the ability to assimilate . Animals depend entirely on diet

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18
Q

how do plants assimilate nitrogen

A

the plants absorb the nitrogen from the soil in the form of Nitrate ( NO3-) and ammonia ( NH3)

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19
Q

In aerobic conditions do we see more nitrate or ammonia

A

nitrate predominates ( NO3-). Ammonia predominates in grasslands

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20
Q

what is the assimilated form of nitrogen for plants

A

ammonia

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21
Q

what are the 2 enzymes needed to convert nitrate into ammonia

A

nitrate reductase N03- + 2e—> NO2-

Nitrite Reductase NO2- +6e —> NH4+

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22
Q

What cofactor is required for nitrate reductase

A

Mo cofactor and NADH

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23
Q

What cofactor is required for nitrite reductase

A

siroheme . This is a heme like prosthetic group. It is synthesized from B12.

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24
Q

Do humans have the glutamine synthase enzyme or the glutamate synthase enzyme

A

we only have the glutamine synthase, no the glutamate synthase

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25
Q

what step is being described : the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment

A

nitrogen assimilation

26
Q

can plants fungi and certain bacteria fix N2 gas

A

no , they depend on the ability to assimilate nitrogen for their needs

27
Q

Do animals depend on organic or inorganic nitrogen from their food

A

organic

28
Q

how is nitrogen transported from root to shoot in plants

A

nitrate is taken up by several nitrate transporters that use a proton gradient to power the transport

29
Q

which pathway incorperates ammonia into amino acids

A

glutamine synthetase- glutamate synthase pathway

30
Q

what is the electron donor in nitrate assimilation via nitrate reductase

A

NADH

31
Q

Can all bacteria do nitrogen fixation

A

no , only certain archea and bacteria can fix atmospheric nitrogen . This special group of bacteria is called diazotrophs

32
Q

what is the name of the special group of bacteria that can fix nitrogen

A

diazotrophs

33
Q

name 3 kinds of diaztrophs that are capable of nitrogen fixation

A

Rhizobia, Frankia , Azospirillium

34
Q

what is unique about diaztrophs that allow them to fix nitrogen

A

they have enzymes that allow them to overcome the high activation energy , by binding and hydrolating ATP

35
Q

what is the important product of nitrogen fixation

A

ammonia

36
Q

describe the nitrogenase complex

A

it is the complex that allows for nitrogen fixation by diazotrophs . The complex has 2 subunits : Dinitrogenase reductase and Dinitrogenase. 16 ATP are consumed .

37
Q

what are the 2 subunits of the nitrogenase complex

A

dinitrogenase reductase and dinitrogenase

38
Q

how many ATP are consumed in the the nitrogenase complex

A

16

39
Q

What 2 cofactors are needed for the nitrogenase complex

A

iron molybedium and vanadium nitrogenase

40
Q

what is one thing that nitrogen assimilation and and nitrogen fixation have in common

A

they are both electron transfer processes, both use a molybidium cofactor

41
Q

is nitrogen fixation an aerobic or anaerobic process?

A

anerobic , because it is very unstable in the presence of oxygen . It only has a half life of 30 seconds in air !

42
Q

what is leghmoglobin

A

It is an 02- binding heme. Many plants live in root nodules coated with this binding protein . This creates the anerobic environment that is needed for nitrogen fixation!

43
Q

what is an annamox bacteria

A

they can take a short cut, no denitrification is needed

44
Q

what does annamox refer to

A

anaerobic ammonia oxidation

45
Q

an annamox bacteria can oxidize NH3 and NO2- into what

A

N2

46
Q

what kind of bacteria are used in waste treatment for cheaper ammonia removal

A

annamox bacteria, because they can oxidize NH3 into NO2- and N2 .

47
Q

ammonia is incorperated into biomolecules thru what to amino acids

A

glutamate and glutamine

48
Q

ammonia enters organic linkages via what 3 reactions

A
  1. glutamine synthase
  2. Glutamate Dehydrogenase
  3. Carbomyl Phosphate Synthetase ( urea cycle)
49
Q

glutamine (Gln) is made from glutamate ( Glu) by what enzyme

A

glutamine synthetase

50
Q

how is glutamate generated

A

it is generated from alpha ketoglutarate via glutamate synthase

51
Q

how is glutamine generated

A

from glutamate via glutamine synthetase

52
Q

is glutamate synthase present in animals

A

no ! we generated glutamate via transamination

53
Q

how do animals generate glutamate

A

through transamination which is catalyzed by aminotransferases

54
Q

what cofactor is required by transamination

A

PLP

55
Q

where does oxidative deaminaition occur

A

in the mitochondrial matrix

56
Q

is ammonia toxic

A

yes , so it must be safely transported in the blood as glutamine

57
Q

explain how excess ammonia in the tissues is transported

A

glutamine uses the enzyme glutamine synthase and turns it into glutamine

58
Q

explain how excess ammonia in the liver is transported

A

glutamine uses the enzyme glutaminase to turn it into glutamine

59
Q

where is the only place where glutaminase is found

A

in liver mitochondria

60
Q

how is ammonia collected by glutamate removed

A

by glutamate dehydrogenase

61
Q

in soil bacteria and plants ________ and _______ convert ___ to _____

A

nitrate reductase, nitrite reductase , NO3- , NH3

Meharry Biochem (17 decks)

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