B5.061 - Nitrogen Balance Flashcards
nitrogen balance =
nitrogen in - nitrogen out
how are carbs stored
glycogen
how are fatty acids stored
TGs
calcuation for nitrogen intake from protein in diet
nitrogen intake = daily protein / 6.25
nitrogen balance equation
nitrogen in - nitrogen out + 4 to account for loss by sweat, feces etc.
zero nitrogen balance
consuming correct amount
negative nitrogen balance
need to increase protein intake
examples of conditions that necessitate positive nitrogen balance
pregnancy, body builder
elevated alanine in a starved person
released from muscle d/t protein breakdown alanine is transporter of NH3 as transports carbon to liver for gluconeogenesis
the brain prefers what energy source
glucose
describe alanines pathway from the muscle to the urine in starved state
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
low levels of glucose in starved state
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
elevated acetoacetate and beta hydrocybutyrate in starvation
d/t ketone body metabolism using fat from body stores due to lack of calories in diet
what cannot be turned to glucose
fatty acids
what can the brain use as an alternative to glucose
ketones
what causes elevated BUN in starvation
increased AA catabolism
rule of thumb for calculating calories from diet
cals/gram
fatty acid - 9
carbs - 4
protein -4
where are BUN and urinary urea nitrogen in the urea cycle
both after the cycle is complete
in the fed state what happens with AAs
converted to glucose and fatty acids primarily in liver
can we store protein
no
where does AA catabolism occur in the body
tissues
where does the urea cycle take place
liver
what is vitamin B6 a cofactor for
coenzyme in AA metabolism
pyridoxal phosphate
what does pyridoxal 5 phosphate do
AA transamination
a B6 derivative
essential AAs
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
glucogenic AAs
The exclusively glucogenic amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, histidine, glutamine, glutamic acid, glycine, serine, methionine, proline, and valine.
ketogenic and glucogenic AAs
The ketogenic and glucogenic amino acids are threonine, tryptophan, tyrosine, isoleucine, and phenylalanine.
ketogenic AAs
leucine and lysine
what is alanine converted to
pyruvate
what is aspartate converted to
oxaloacetate
what is glutamate converted to
alpha ketogluterate
what is Asn converted to
Asp –> oxaloacetate
what is serine converted to
pyruvate
what is cystein converted to
pyruvate
what is threonine converted to
acetyl coa and glycine
what is Phe converted to
Tyr
describe the urea cycle
does the urea cycle continue in starvation
yes!
how do you get glutamate in the starvation state
alanine is converted to pyruvate and glutamate via alpha ketogluterate
how do you get alpha ketoglutarate in the starved state
from alanine via pyruvate, pyruvate enters the TCA and makes alpha keto glutarate
how do you get aspartate in starved state
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
what role does glutamate have in the urea cycle
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
what does carbamoyl phosphate synthase do
converts ammonia and HCO2 into carmaboy phosphate
what does carbamoyl phosphate do
combines with ornithine to make citrulline via ornithine transcarbamoylase
what does citrulline do
combines with aspartate to make argininosuccinate via argininosuccinate synthetase
what does argininosuccinate do
loses fumarate and converts to arginine via argininosuccinase
what does arginine do
loses urea and converts to ornithine via arginase
during periods of high protein breakdown what happens with glutamate
increased glutamate, signals need for increaed ureae cycle flux by activating cabamoyl phosphate synthetase
what happens in the kidney during starvation
increased glutamine is converted to ammonia and glucose and its excreted
what is arginine essential for
its present in urea cycle, we dont make enough to sustain what we need though
normal breakdown of Phe
Phe + BH4 +O2 –> Tyr + BH4 + H2O
BH4 = tetrahydrobiopterin
Tyr non an essential AA
what is phenylketonuria
phenylalanin hydroxylase isnt working and Phe cant make Tyr thus in these people Tyr is essential
what is biopterin
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
can you OD on protein
yeah its called obesity duh
what is maple urine disease
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
