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Nitrogen Metabolism/ Urea Cycle Biochemistry
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What is the most prevalent neurotransmitter?
Glutamate
What does glutamate readily converts into?
Glutamine
Glutamate has how many carbons? Aspartate?
5 carbons for glutamate
4 carbons for aspartate
Glutaminase degrade _____ to form _____
Glutamine
Glutamate
Glutamine synthetase converts ____ to ____
Glutamate
Glutamine
Ornithine, citrulline and arginine are all compounds formed from ______
Glutamate
What is the source of most of the body’s ammonia?
Bacteria reducing N2 into ammonia
True/false: half the dry weight of urine is uric acid
True
False
False; it is urea
What is the committed step of the urea cycle?
Carbamoyl phosphate synthetase
Which is the rate limiting step of the urea cycle?
Carbamoyl phosphate synthetase
What is carbamoyl phosphate important for?
Urea cycle
Pyrimidine biosynthesis
True/False: energy is used to turn carbonic acid into carbamoyl phosphate
True
False
True, two molecules of ATP
True/False: ammonia released from glutamine or glutamate enter the urea cycle as carbonic acid
True
False
False; it enters the urea cycle as carbamoyl phosphate
How is pyrimidine biosynthesis come about?
Carbamoyl phosphate becomes carbamoyl aspartate, then dihydroorotate and orotate
From that it reacts with PRPP and eventually pyrimidine
What are the four organs involved for nitrogen metabolism?
Kidneys
Intestine
Liver
Brain
Where does N2 mostly come from?
Intestine, mainly the bacteria
Ammonia is converted to which compound when it is getting exported out of the blood?
Glutamine
Liver ____ nitrogen and kidneys _____ them
Metabolize
Excrete
Which is the inert harmless transporter to move ammonia from brain to the liver?
Glutamine
How many ammonia can each glutamine transport?
Two ammonia molecules
What is the function of transaminase?
Interconvert between amines and ketones
What enzyme produce glutamine in the brain?
Glutamine synthetase
What enzyme produce alanine in muscle?
Alanine transaminase
Which enzymes produce ammonia in liver?
Glutaminase
Glutamate dehydrogenase
Which enzymes produce ammonia in the kidneys?
Glutaminase
Glutamate dehydrogenase
In which type of cells do glutamine or glutamate release nitrogen in the form of ammonia?
Hepatocytes
Where does the urea cycle occurs?
Hepatocytes
Which cell exports urea into blood for transport to kidneys?
Hepatocytes
Where does nitrogen metabolism occur/ urea formation?
Liver
True/False: kidney is where urea is made
True
False
False; urea is made in the liver and kidney excretes it
Which three urea cycle enzymes are found in the mitochondrial matrix?
N-acetyl glutamate synthase
Carbamoyl phosphate synthetease
Ornithine transcarbamylase
Which three urea cycle enzymes are found in the cytosol?
Argininosuccinate synthetase
Argininosuccinate lyase
Arginase
What results with loss of function mutations of N-acetylglutamate synthase?
Decrease ability to upregulate carbamoylphosphate synthetase
Leads to hperammonemia
True/false: ammonia comes from glutamate/glutamine deamination
True
False
True
Which urea cycle intermediate is formed in the cytosol and transported back to the mitochondrial matrix
Ornithine
How many nitrogens in urea molecule and where did they come from?
2
One from carbamoyl phosphate
One from arginine
True/false: ornithine transcarbamylase deficiency is an X linked dominant disorder
True
False
False; it is X linked recessive
Loss of function is typically _____ mutations
Recessive
What are some immediate emergent treatment for hyperammonemia?
Dialysis
NG tube lactulose
Why is lactulose the most widely used pharmaceuticals for hyperammonemia?
Because bacterial will eat lactulose and will lower pH of blood, therefore ammonia has a 100 fold drop
Rate of ammonia/ammonium drops ____ fold when treating it with lactulose
100
Which enzyme moves aspartate and glutamate in and out of the mitochondria?
Citrin
What is the HHH syndrome?
Hperornithinemia-hperammonemia-homocitrullinurea
Loss-of-function mutation to the ornithine carrier
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Author
lykthrnn
ID
346144
Card Set
Nitrogen Metabolism/ Urea Cycle Biochemistry
Description
Renal Midterm- Biochemistry
Updated
2019-03-27T01:25:26Z
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