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Biochem nitrogen Metabolism
KYCOM Block 4
84
Biochemistry
Graduate
11/30/2012

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Term
what substances does nitrogen metabolism include
Definition
amino acids, proteins, heme, nucleotide metabolism
Term
how is nitrogen stored
Definition
it isnt
Term
why do we need to get rid of nitrogen
Definition
there is no way to store it and it is reactive in the body
Term
where are most amino acids obtained
Definition
diet, protein turn over, synthesis of non-essential amino acids
Term
what are amino acids used for
Definition
systhesis of proteins, synthesis of nitrogen containing compounds (nucleotides, heme), use of carbond skeletons of amino acids to make compounds for energy
Term
define nitrogen balance
Definition
net loss/ gain of amino acids to the bodys pool
Term
what is the half life of a protein related to
Definition
function and structure
Term
what condition would cause a protein to degrade more rapidly
Definition
misfolded or unstable proteins
Term
what causes a glucose-6-phosphate dehydrogenase deficiency
Definition
it is degraded in a deficiency because of a missense mutation making it less stable
Term
what structure characteristics of proteins would affect protein degredation or half life
Definition
amino acid at the N terminus (because it determines post translational modifications), PEST sequence codes for early degradation
Term
what are the ways to degrade proteins
Definition
lysosomal, proteasomes
Term
how are proteins sent to proteasomes to be degraded
Definition
tagged with ubiquitin
Term
what proteins are degraded by the lysosome
Definition
extracellular and membrane bound
Term
skipping enzyme process, give the general layour for the path of protein drgration starting with ingestion
Definition
1. low pH in stomach denatures
2. pepsin in the stomach
3. small intestine stimulation by CCK and secretin
4. zymogens released by pancreas
5. only single AA remain
6. AA absorbed and go to liver to decide their fate
Term
what are the purposes for the low pH in the stomach
Definition
primairly to kill microbes but also denatures proteins
Term
what type of enzyme is pepsin
Definition
endopeptidase
Term
how is pepsin made
Definition
zymogen cell releases pepsinogen and the low pH of the stomach activates it to pepsin
Term
what can pepsin do
Definition
digest proteins or turn more pepsinogen into pepsin
Term
what stimulates for the release of enzymes from the pancreas
Definition
chyme enters the small intestines stimulating CCK and secretin release, they then stimulate the pancreas
Term
what are examples of active pancreatic enzymes
Definition
chymotrypsin, trypsin
Term
how is trypsin made
Definition
the pancreas releases trypsinogen into the small intestines, intestinal cells release enteropeptidase which activates trypsinogen into trypsin
Term
what can trypsin do
Definition
it can activate other pancreatic enzymes or turn more trypsinogen to trypsin
Term
what turns chymotrypsinogen into chymotrypsin
Definition
trypsin
Term
what turns pancreatic zymogens into acrive enzymes
Definition
trypsin
Term
how are pancreatic enzymes classified
Definition
endopeptidases, exopeptidases
Term
what is an endopeptidase
Definition
cleaves inside a peptide sequence
Term
what is an exopeptidase
Definition
cleaves from the ends of a peptide sequence
Term
what are issues with protein digestion associated with
Definition
other diseases that affect the pancreas like cystic fibrosis, pancreatitis
Term
what is another name for celiac disease
Definition
celiac spruse
Term
what causes the symptoms of celiac diasese
Definition
the intestines have an allergic reaction to gluten damaging intestinal cells leading to malabsorption
Term
what causes cystinuria
Definition
kidney cant absorb some amino acids causing them to accumulate, percipitate and cause kidney stones
Term
what is cystine
Definition
2 cysteines
Term
why are the amino acids involved with cystinuria grouped the way they are
Definition
because they have a common transporter
Term
what amino acids cant be absorbed in cystinuria
Definition
cystine, ornithine, lysing, arginine
Term
what is another name for kidney stones
Definition
calculi
Term
in what forms is nitrogen transported
Definition
glutamate, glutamine, alanine, aspartate
Term
what is a majority of nitrogen transported as
Definition
glutamate
Term
what makes glutamate
Definition
a-ketogluterate and NH3
Term
what makes glutamine
Definition
glutamate and NH3
Term
what makes alanine
Definition
pyruvate and NH3
Term
what makes aspartate
Definition
OAA and NH3
Term
what are the types of aminotransferases
Definition
alanine amino transferase (ALT), asparatate amino transferase (AST)
Term
what can aminotransferases be indicators of, where are they
Definition
tissue damage (heart attack, liver damage), in the blood
Term
what does aminotransferase need to work
Definition
pyridoxal phosphate cofactor
Term
where does pyridoxal phosphate come from
Definition
derived from vitamin B6
Term
what does amino transferase convert
Definition
it combines a-ketogluterate and an amino acid to make glutamate and a-ketoacid or vice versa
Term
what is the difference between aminotransferase and glutamate DH
Definition
with glutamate DH ammonia is a product or substrate instead of transferred
Term
where is glutamate DH mostly located
Definition
kidney and liver
Term
what does glutamate DH convert
Definition
glutamate and NAD into a-ketogluterate, NADH, and NH3 or in reverse
Term
what is the normal function of glutamine synthase
Definition
mostly in tissues to get their nitrogrn into the blood to go to the liver
Term
what does glutamine synthase convert
Definition
glutamate, ATP, NH3 into ADP and glutamine
Term
what does glutaminase convert
Definition
glutamine and ADP into ARP, NH3, and glutamate
Term
what is the normal function of glutaminase
Definition
release ammonia and glutamate at the liver
Term
in general, what is the major route of nitrogen disposal
Definition
tissue sends out glutamine (alanine in muscle), it is taken up by the liver, then into the urea cycle
Term
after nitrogen disposal where do carbon skeletones go
Definition
into biosynthetic pathways
Term
what is the main system for nitrogen disposal
Definition
the urea cycle
Term
explain how the urea cycle is completely recyclable
Definition
C and O are released as CO2 and amino comes from free ammonia and asparatate, C used as carriers are regenerated
Term
what is the first enzyme in the ures cycle
Definition
carbomyl phosphate synthase 1
Term
what is the rate limiting enzyme in the urea cycle
Definition
carbomyl phosphate synthase 1
Term
what increases the transcription of carbomyl phosphate synthase 1
Definition
acetylglutamate
Term
what increases acetylglutamate production
Definition
acetyl CoA, glutamate, arginine
Term
what can cause am increase in acetyl CoA, glutamate, and arginine
Definition
a high protein meal
Term
what does carbomyl phosphate synthase 1 catalyze
Definition
ammonia, CO2, and ATP to carbomyl phosphate
Term
what is the second enzyme in the urea cycle
Definition
ornathine transcarbomylase
Term
what does ornathine transcarbomylase catalyze
Definition
ornathine and carbomyl phosphate to citrulline
Term
where do the first two steps in the urea cycle take place in
Definition
the mitochondria
Term
what intermediates in the urea cycle can go through the mitochondrial membrane
Definition
citrulline, ornithine
Term
after citrulline enters the cytoplasm, what happens to it in the urea cycle
Definition
it joins asparatate adding another amino grouop, it goes through common sugar intermediates, under the enzyme arginase releases free urea, turns back into ornithine
Term
where does free urea released from the urea cycle go
Definition
from the liver to the blood then kidney to urine
Term
how is ammonia and asparatate gotten into the liver cell
Definition
1. a-ketogluterate is converted to glutamate
2.A. glutamate DH turns it into ammonia
2.B. aminotransferase turns it into aspartate
Term
what places in the body does ammonia come from
Definition
tissues, diet, microbes, exogenous enzymes, muscle, kidney
Term
how does ammonia from the tissues, diet, microbes in the gut, and exogenous enzymes get to the liver
Definition
ammonia + glutamate --glutamine synthase--> glutamine --> sent to liver
Term
how does ammonia from the muscle get to the liver
Definition
ammonia + pyrivate --glutamine synthase--> alanine --> sent to the liver
Term
what happens to glutamine and alanine once they get to the liver
Definition
glutaminase turns them into ammonia and glutamate/pyruvate
Term
what happens to ammonia produced by the kidney, what other function does this play
Definition
it is excreted into the urine, can also contribute to the body's acid base balance
Term
define hyperammonemia
Definition
elevated ammonia in the blood
Term
what are the causes of hyperammonemia
Definition
liver failure, liver dysfunction, urea cycle enzyme defect
Term
what is a urea cycle enzyme defect classified as
Definition
inborn error of metabolism
Term
what are the effects / symptoms of hyperammonemia
Definition
mental redardation and death due to nervous tissue effects, shows up shortly after birth
Term
what is a type of hyperammonemia disease
Definition
ornithine transcarbomylase deficiency
Term
what is the inheritance of ornithine transcarbomylase deficiency
Definition
x-linked
Term
what is the treatment for hyperammonemia
Definition
diet motification (low protein), phenylbuterate
Term
what is the reaction phenylbuterate causes in the body
Definition
once in the body it is naturally comverted to phenylacetate which combines with glutamate to make phenylacetylglutamine, the kidney will absorb that and put it in urine
Term
explain the theory behind how phenylbuterate works
Definition
glutamine is made for protein synthesis, removing N lessening the urea cycle need, reducing ammonia
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