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Biol214 > Nitrogen metabolism > Flashcards

Nitrogen metabolism Flashcards

1
Q

nitrogen is found mostly in ??? and proteins

A

nucleic acids and proteins

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2
Q

TRUE or FALSE: nitrogen can be found in:
- several cofactors (NAD, FAD, biotin, etc)
- many small hormones (epinephrine)
- many neurotransmitters (serotonin)
- many pigments (chlorophyll)
- many defence chemicals (amanitin in mushrooms)

A

TRUE

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3
Q

what causes nitrogen to be virtually unusable by most organisms?

A

the highly resistant triple bond

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4
Q

??? is the main process by which nitrogen-fixing bacteria and archea convert N2 to NH3 (biologically useful form)

A

nitrogen fixation

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5
Q

TRUE or FALSE: Ammonia can be used by all organisms either directly or indirectly, after it has been converted to nitrites, nitrates or
amino acids

A

TRUE

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6
Q

N2 and O2 → NO via lightning
(represents ???% of newly fixed N2)

A

25%

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7
Q

N2 and H2 → NH3 (ammonia) via the
industrial Haber (Haber-Bosch) process (requires T > 400°C, P > 200 atm; represents ???% of newly fixed N2) (partly helped through ATP hydrolysis)

A

15%

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8
Q

Fixation is the Reduction or Oxidation of N2 → NH3
/NH4+ (ammonia/ammonium)

A

Reduction

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9
Q

Nitrification occurs when Bacteria Oxidise or Reduce NH3 into NO2– (nitrite) and NO3– (nitrate)

A

oxidise

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10
Q

Denitrification is the process where NO3– / NO2– is Reduced or Oxidised to N2 under anaerobic conditions

A

Reduced

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11
Q

TRUE or FALSE:
Anammox: Anaerobic ammonia oxidation = alternative pathway back to N2

A

TRUE

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12
Q

Assimilation: Plants and microorganisms reduce NO3– and NO2– to NH3/NH4+ via nitrate ??? and nitrite ???

A

reductases

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13
Q

Following Fixation or Assimilation
ammonia in its reduced form (NH4+) is assimilated into ??? and
biomolecules ==> Nitrogen CYCLE part of nitrogen web

A

amino acids

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14
Q

Nitrogen CYCLE part of nitrogen web where:
1. Animals eat plants as source of ???
2. NH4+ in plants is incorporated into AAs and other N-containing biomolecules
3. Organisms die, return NH4+ to soil.
4. Nitrifying bacteria again convert NH4+ /NH3 to NO2– and NO3–

A

amino acids

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15
Q

TRUE or FALSE: transamination does NOT provide nitrogen

A

FALSE it is a source of nitrogen

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16
Q

??? is the transfer of an amino group from one molecule to another

A

Transamination

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17
Q

transamination is catalysed by ??? and use pyridoxal phosphate (PLP) as a cofactor

A

aminotransferases

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18
Q

Transamination as N source:
- L-Glutamate acts as a temporary storage of N
- L-Glutamate DONATES or RECEIVES the amino group when needed for amino acid biosynthesis = readily reversible
- Glutamate is the source of amino groups for most other amino acids in mammals

A

DONATES

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19
Q

Transamination as N source:
α-ketoglutarate + L-amino acid <–> L-??? + α-ketoacid

A

glutamate

20
Q

Ammonia (NH4+) is Incorporated into Biomolecules through Glutamate and ???

A

Glutamine

21
Q

Glutamine is made from ??? by glutamine synthetase in a two-step process.
1. Phosphorylation of ??? creates a good leaving group that can be easily displaced by ammonia
2. glutamate dehydrogenase -
catalyses the incorporation of ammonium into α-ketoglutarate to produce ???

A

glutamate
glutamate
glutamate

22
Q

The enzyme - glutamate dehydrogenase - catalyses the incorporation of ammonium into
??? to produce glutamate

A

α-ketoglutarate

23
Q

TRUE or FALSE: incorporation of ammonium into α-ketoglutarate to produce glutamate is the minor pathway of glutamate formation

A

TRUE

24
Q

What enzyme is a Primary Regulatory Point in Nitrogen Metabolism?

A

glutamine synthetase

25
Q

glutamine synthetase plays a central role in the conversion of toxic free NH3 to glutamine and in the metabolism of ???

A

amino acids

26
Q

glutamine synthetase undergoes ??? regulation by six end products of glutamine metabolism

A

cumulative

27
Q

glutamine synthetase is regulated by ??? regulation and inhibited by adenylylation

A

allosteric regulation

28
Q

Adenylylation is a post-translational modification whereby AMP binds to a hydroxyl group of a molecule via adenylyltransferase, inhibiting ???

A

glutamine synthetase

29
Q

Adenylylation is indirectly inhibited by α-ketoglutarate and ATP to stop inhibiting ???

A

glutamine synthetase

29
Q

Adenylylation is indirectly stimulated by glutamine and Pi to inhibit ???

A

glutamine synthetase

30
Q

amino acid biosynthesis is through catabolism or anabolism?

A

anabolism

31
Q

Carbon skeletons come from intermediates of
* Glycolysis
* Citric acid cycle
* ???

A

Pentose phosphate pathway

32
Q

TRUE or FALSE: A deficiency of one amino acid does not impact the synthesis of all proteins required for life, it only impacts a few that share similar pathways

A

FALSE: A deficiency of one amino acid
impacts the synthesis of all
proteins required for life

33
Q

a-ketoglutarate, pyruvate, 3-phosphoglycerate, oxaloacetate, ribose-5-phosphate and phosphoenolpyruvate + erythrose 4-phosphate are the 6 major NON-ESSENtial or ESSENTIAL Amino Acid Biosynthetic Families?

A

NON-ESSENTIAL

34
Q

Nonessential amino acids (except Arg) are synthesised by simple reactions ??? steps

A

1-5

35
Q

Essential amino acids are synthesised by more complex reactions ??? steps

A

5-16 steps

36
Q

Regulation of threonine deaminase: Threonine is converted into
a-ketobutyrate in the committed step = synthesis of isoleucine.
??? catalyzes this step and is inhibited by isoleucine (its product) and activated by valine, the product of a parallel pathway.

A

threonine deaminase

37
Q

CATABOLISM or ANABOLISM of amino acids accounts for only 10-15% of energy production

A

CATABOLISM

38
Q

Glycolysis and fatty acid oxidation
are more active than the catabolism of ??? in the production of energy

A

aminoa cids

39
Q

Catabolic pathways converge to 6-7
major products, all which enter TCA cycle. From here the carbon skeletons can be used for gluconeogenesis or formation of
??? bodies

A

ketone bodies

40
Q

decarboxylation reactions turn amino acids into neurotransmitters such as ??? which are correlated with, among other things,
changes in blood pressure and neuro/psychiatric disorders.

A

catecholamines

41
Q

amino acids also undergo decarboxylation reactions during hormone synthesis, i.e. y-aminobutyrate and ???

A

histamine

42
Q

Glutathione (GSH) is present in most cells at high amounts and is a reducing agent/???

A

antioxidant

43
Q

GSh keeps proteins and metal cations reduced, keeps redox enzymes in a ??? state and removes toxic reactive oxygen species (ROS)

A

reduced

44
Q

Glutathion (GSH) is Oxidized or Reduced to a dimer (GSSG

A

Oxidised

45
Q

TRUE or FALSE: nitric oxide is important biologically for neurotransmission, blood pressure regulation, blood clotting and immunity

A

TRUE

46
Q

Nitric Oxide is synthesised from ??? via nitric oxide synthase using NADPH

A

Arginine

Biol214 (12 decks)

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