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NSF > nitrogen > Flashcards

nitrogen Flashcards

1
Q

N2 cycle

A

process (biological + physical) by which N2 converted bet various chem forms
1. fixation
2. ammonification
3. nitrification
4. denitrification

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2
Q

symbiotic nitrogen fixation

A

N2 in air -> NH3/NH4+ for use by plants
* carried out by nitrogenase complex (dinitrogenase reductase + dinitrogenase)
* plant has mutualistic relationship w nitrogen-fixing bac, e.g. Rhizobium = can survive independently but benefit each other - provide NH3 + carbs respectively

in plants harbouring N2-fixing bac w/in tissues = DONE IN PLANTS

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3
Q

major storage form N in soil

A

NO3-

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4
Q

conversion soil nitrate + nitrite to ammonia

w equs

A

reduction NO3- + NO2- to NH3 in bac in soil/in plants as required for building blocks make aas

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5
Q

how is NH3 present in plants

A

usually as NH4+ at physiological pH (7.4)

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6
Q

incorporation NH3 into aas

A
  1. NH3 -> glutamate using glutamate dehydrogenase
  2. glutamate -> glutamine using glutamine synthase
rhs glutamine may be dissociated in sol
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7
Q

which aas synthed from glutamate

A
  1. glutamine
  2. proline
  3. arginine - missing final part synth pathway in mammals = can’t make, have to eat
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8
Q

transamination

A

transfer of amino grp (-NH2) bet aas - usually from glutamate

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9
Q

role of precursor in citric acid cycle for biosynth aas

A

oxaloacetate precursor aspartate, which is a precursor for other aas, all part aspartate family

of these, only asparagine has biosynthetic pathway for synth in animals

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10
Q

how is asparagine synthed from aspartate

A

transfer amine grp from glutamine to aspartate by asparagine synthase

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11
Q

biosynth precursor serine family aas

A

3-phosphoglycerate

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12
Q

aas for which pyruvate precursor

A

alanine, valine, leucine
* only alanine has biosynthetic pathway in mammals

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13
Q

essential vs non-essential aas defn

A

aas that must be provided in diet to meet animal’s metabolic needs
non-essential = no need provide as can be biosynthed in adequate amounts
some non-essential become essential in growth/illness - need start eating it as can’t make

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14
Q

list essential aas

A
  • arginine
  • histidine
  • isoleucine
  • leucine
  • lysine
  • methionine
  • phenylalanine
  • threonine
  • tryptophan
  • valine
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15
Q

use tryptophan

A

precursor for serotonin (NT) - marketed sleep aid + antidepressant

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16
Q

use leucine

A

additive flavour enhancer - slows degradation muscle by increasing muscle prot in ageing rats

17
Q

use methionine

A

racemic mix added pet foods

18
Q

biogenic amines - how formed, examples w precursor + function

table

A

formed decarboxylation aas

19
Q

pathway for catecholamine biosynth

A
tyrosine hydroxylase limits rate whole synth
20
Q

glucogenic vs ketogenic aas

try to give degradation products

A

glucogenic broken down to citric acid cycle intermediates
* can be converted to glucose by gluconeogenesis

ketogenic broken down to acetyl-CoA or acetoacetate
* can be converted to ketone bodies (= emergency fuel source)

some aas are both

+ = both glucogenic + ketogenic
21
Q

how are aas broken down for excretion mammals

A
  1. Transamination: aa gives amine grp to α-ketoglutarate = glutamate, cated aminotransferase/transaminase
  2. Deamination: glutamate broken down to α-ketoglutarate by glutamate dehydrogenase, releasing NH4+
  3. NH4+ used make urea
  4. urea is safe for excretion
22
Q

how is NH3 excreted

A

free NH3 excreted by conversion to urea in urea cycle in liver as free NH4+ toxic bc reacts w lots things

23
Q

How is nitrogen in NH4+ transported to liver

for conversion to urea

A

ammonium ions converted to alanine or glutamine for transport in blood
* alanine then converted to glutamate + deaminated in liver

24
Q

how is urea excreted

A
  • in mammals by the kidneys + in saliva + sweat
  • in ruminants into GI sys where can be reused for aa biosynth
25
Q

N2 excretion in aquatic animals

A

directly excrete ammonium = ammonotelic
* NH4+ gened in gills by deamination, secreted + rapidly diluted in aquatic environ

sharks + cartilaginous fish can prod urea asw as NH3

26
Q

nitrogen excretion in birds + reptiles

A

excrete N2 as uric acid = ureotelic
* conserves water even though uses relatively large amount E
uric acid formed following generation aspartate, glutamine, glycine, then synth purine nucleotides - degradation purine prods uric acid

also occurs in mammals + fish but not primary route N2 excretion

27
Q

ruminant nitrogen metabolism

A
  1. prots hydrolysed to aas by ruminal microbes
  2. prots that escape digested in SI where aas absorbed
  3. ruminal microbes use aas for own prot synth or degrade them further to ammonia
  4. some ammonia to liver for conversion to urea + excretion
  5. rumen microbes fix ammonia into aas - can make any want, used make microbial prots
  6. microbial prots digested + absorbed in SI

can reabsorb urea, used make aas + incorporated prots

NSF (22 decks)

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