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GIR Test 3 > B5.061 - Nitrogen Balance > Flashcards

B5.061 - Nitrogen Balance Flashcards

1
Q

nitrogen balance =

A

nitrogen in - nitrogen out

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2
Q

how are carbs stored

A

glycogen

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3
Q

how are fatty acids stored

A

TGs

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4
Q

calcuation for nitrogen intake from protein in diet

A

nitrogen intake = daily protein / 6.25

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5
Q

nitrogen balance equation

A

nitrogen in - nitrogen out + 4 to account for loss by sweat, feces etc.

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6
Q

zero nitrogen balance

A

consuming correct amount

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7
Q

negative nitrogen balance

A

need to increase protein intake

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8
Q

examples of conditions that necessitate positive nitrogen balance

A

pregnancy, body builder

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9
Q

elevated alanine in a starved person

A

released from muscle d/t protein breakdown alanine is transporter of NH3 as transports carbon to liver for gluconeogenesis

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10
Q

the brain prefers what energy source

A

glucose

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11
Q

describe alanines pathway from the muscle to the urine in starved state

A

alanine in blood –>

alanine in liver –>

alanine is converted to pyruvate and glutamate via alpha ketoglutarate –>

glutamate is converted to aspartate and NH3

Those are combined to make urea

pyruvate enters gluconeogenesis pathway

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12
Q

low levels of glucose in starved state

A

even with increased alanine generated from muscle mass breakdown, there is not enough carbon source to support gluconeogenic flux to compensate for lack of dietary glucose

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13
Q

elevated acetoacetate and beta hydrocybutyrate in starvation

A

d/t ketone body metabolism using fat from body stores due to lack of calories in diet

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14
Q

what cannot be turned to glucose

A

fatty acids

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15
Q

what can the brain use as an alternative to glucose

A

ketones

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16
Q

what causes elevated BUN in starvation

A

increased AA catabolism

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17
Q

rule of thumb for calculating calories from diet

A

cals/gram

fatty acid - 9

carbs - 4

protein -4

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18
Q

where are BUN and urinary urea nitrogen in the urea cycle

A

both after the cycle is complete

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19
Q

in the fed state what happens with AAs

A

converted to glucose and fatty acids primarily in liver

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20
Q

can we store protein

A

no

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21
Q

where does AA catabolism occur in the body

A

tissues

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22
Q

where does the urea cycle take place

A

liver

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23
Q

what is vitamin B6 a cofactor for

A

coenzyme in AA metabolism

pyridoxal phosphate

24
Q

what does pyridoxal 5 phosphate do

A

AA transamination

a B6 derivative

25
Q

essential AAs

A

Mnemonic: “Help In Learning These Little Molecules Proves Truly Valuable”
Help = Histidine
In = Isoleucine
Learning = Leucine
These = Threonine
Little = Lysine
Molecules = Methionine
Proves = Phenylalanine
Truly = Tryptophan
Valuable = Valine

also arginine bc we dont make enough

26
Q

glucogenic AAs

A

The exclusively glucogenic amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, histidine, glutamine, glutamic acid, glycine, serine, methionine, proline, and valine.

27
Q

ketogenic and glucogenic AAs

A

The ketogenic and glucogenic amino acids are threonine, tryptophan, tyrosine, isoleucine, and phenylalanine.

28
Q

ketogenic AAs

A

leucine and lysine

29
Q

what is alanine converted to

A

pyruvate

30
Q

what is aspartate converted to

A

oxaloacetate

31
Q

what is glutamate converted to

A

alpha ketogluterate

32
Q

what is Asn converted to

A

Asp –> oxaloacetate

33
Q

what is serine converted to

A

pyruvate

34
Q

what is cystein converted to

A

pyruvate

35
Q

what is threonine converted to

A

acetyl coa and glycine

36
Q

what is Phe converted to

A

Tyr

37
Q

describe the urea cycle

A
38
Q

does the urea cycle continue in starvation

A

yes!

39
Q

how do you get glutamate in the starvation state

A

alanine is converted to pyruvate and glutamate via alpha ketogluterate

40
Q

how do you get alpha ketoglutarate in the starved state

A

from alanine via pyruvate, pyruvate enters the TCA and makes alpha keto glutarate

41
Q

how do you get aspartate in starved state

A

alanine is converted to glutamate and pyruvate via alpha ketogluterate

pyruvate is converted to oxaloacetate via pyruvate carboxylase

oxaloacetaet enters TCA and combines with glutamate to make aspartate and alpha ketogluterate

42
Q

what role does glutamate have in the urea cycle

A

N-acetyl-glutamate is an oblicate activator of carbamoyl phosphate synthase 1 which is the first step of converting CO2 and ammonia to carbamoyl phosphate

43
Q

what does carbamoyl phosphate synthase do

A

converts ammonia and HCO2 into carmaboy phosphate

44
Q

what does carbamoyl phosphate do

A

combines with ornithine to make citrulline via ornithine transcarbamoylase

45
Q

what does citrulline do

A

combines with aspartate to make argininosuccinate via argininosuccinate synthetase

46
Q

what does argininosuccinate do

A

loses fumarate and converts to arginine via argininosuccinase

47
Q

what does arginine do

A

loses urea and converts to ornithine via arginase

48
Q

during periods of high protein breakdown what happens with glutamate

A

increased glutamate, signals need for increaed ureae cycle flux by activating cabamoyl phosphate synthetase

49
Q

what happens in the kidney during starvation

A

increased glutamine is converted to ammonia and glucose and its excreted

50
Q

what is arginine essential for

A

its present in urea cycle, we dont make enough to sustain what we need though

51
Q

normal breakdown of Phe

A

Phe + BH4 +O2 –> Tyr + BH4 + H2O

BH4 = tetrahydrobiopterin

Tyr non an essential AA

52
Q

what is phenylketonuria

A

phenylalanin hydroxylase isnt working and Phe cant make Tyr thus in these people Tyr is essential

53
Q

what is biopterin

A

BH4, not an essential part of diet

but if a mutation in phe hydroxylase reduces enzyme affinity for BH4, increasing levels of biopterin could help

54
Q

can you OD on protein

A

yeah its called obesity duh

55
Q

what is maple urine disease

A

Branched chain ketoaciduria (maple syrup urine disease) is a defect in the branched chain α-ketoacid dehydrogenase complex (BCKD). The defect in this enzyme causes an inability to metabolize branched-chain amino acids, and subsequent excretion of these amino acids in the urine.

c

The branched chain α-ketoacid dehydrogenase enzyme complex catalyzes the breakdown of the branched chain amino acids:

Isoleucine

Leucine

Valine

Mnemonic: I Love Vermont maple syrup from trees with branches.

autosomal recessive

GIR Test 3 (6 decks)

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