Exam 3 Lecture 4 Flashcards
________ is the disposal form of amino groups
Urea is the disposal form of urea groups
Urea is synthesized as part of the urea cycle, either from ______ or from ______
Urea is synthesized in the urea cycle either from oxidation of amino acids or from ammonia
Approximately ___ of AAs are reutilized
Excess of AA are not stored —-> forms _____
Approx 75% of AAs are reutilized
Excess of AAs are not stored… forms urea and gets excreted
In the urea cycle, amino groups donated by ______ are converted to urea, while ____________ act as intermediates
Urea production occurs in the ____ and us regulated by ______ and excreted through kidney
In the urea cycle, amino groups donated by ammonia and L aspartate are converted to urea, while L-ornithine, citrulline, L arginosuccinate, and L-arginine act as intermediates
Urea production occurs in the liver, and is regulated by N-acetylglutamate then excreted through kidney
What energy sources go into making urea
Synthesis of urea requires 3 mol ATP and an AMP
Urea is found dissolved in the blood…what is the normal range
What is urea excreted as
Urea is found dissolved in blood (range of 2.5 to 6.7 mmol/liter)
Urea is excreted as urine
(small amount of urea excreted as sweat)
In mamals, the urea cycle takes place primarily where?
What compound does the urea cycle start and end with?
In mammals, urea cycle takes place in the liver, to a lesser extent in the kidney
The urea cycle starts and ends with Ornithine
What are the five enzymes required in the urea cycle?
urea cycle enzymes:
Carbamoyl-P synthetase (CPS-1)
Ornithine Transcarbamoylase (OTC)
Argininosuccinate synthetase (ASS)
Argininosuccinate lyase (ASL)
Arginiase (ARG1)
What is the overall reaction for the urea cycle?
Overall reaction:
aspartate + NH3+ CO2+ 3ATP + 3 H20 ——->
urea + fumarate + 2ADP + AMP + 4 Pi
What is the major regulated step of the urea cycle?
Major regulated step of the urea cycle:
Formation of carbomyl phosphate by the enzyme CPS-1
Absolute requirement for N-acetylglutamate for this reaction
What is an important entry point in the urea cycle?
What is the major regulated step of the urea cycle?
Major regulated step is formation of carbmoyl phosphate done by the enzyme carbamoyl phosphate synthetase
ABSOLUTE requirement of N-acetylglutamate for the synthetase
What is the first amino group that enters the urea cycle?
Carbamoyl phosphate
Draw the urea cycle
Ordinarily careless crappers are also frivilous about urinating:
ornithine, carmaboyl phosphate, critrulline, aspartate, arginosuccinate, fumarate, aspartate, urea
Explain the linkage between the urea cycle and the TCA cycle:
fumarate is converted to ____ in the cytosol where it is then converted to _____ in the TCA cycle
OAA is transaminated and transported into the cytosol to form
Fumarate is converted to malate in cytosol, sent to mito to enter TCA cycle to be converted into OAA
Explain the concequences of the various defeciencies:
Carbamyl Phosphate synthetase
Ornithine transcarbamoylase
Arginosuccinate synthetase
Arginase
Carbamoyl phosphate synthetase defeciency: hyperammoneia
Ornithine defeciency: mental retardation and death
Arginosuccinate synthetase: excess of cirtulline in the blood and urine
Arginase: rare defeciency, developmental problems
Metabolic disorders or urea synthesis have dire concenquences.
Arise from abnormal function of enzyme and enzyme defeciencies, often cause_____ and ______
Therapy?
Often cause coma and death
Therapy:
limit protein intake
remove excess ammonia
replace intermediates
liver transplant
_________ is a precursor of citrulline and arginine
______ is synthesized from 3-phosphoglycerate
Ornithine is a precursor of citrulline and arginine
Serine is synthesized from 3-phosphoglycerate
(Serine is a precursor of glycine and D-serine)
Ornithine ———> _____
Shared intermediate is?
Ornithine ——> proline
Shared intermediate: glutamic semialdehyde
3- phosphoglycertate———-> ________
3-phosphoglycerate goes to serine
How can glutamate, alanine, and asartate get broken down?
How does serine get degraded?
How are ornithine and proline degraded?
Glutamate, alanine, and aspartate are deaminated by glutamate dehydrogenase
Serine gets degraded to 3 phosphoglycerate via dephosphorylation (note serine can also go to glycine)
Ornithine and proline degrade via glutamic semialdehyde
Proline hydroxylation requires _______
What happens when you don’t have it
Proline hydroxylation requires ascorbic acid (vitamin C)
The most obvious first effects (gum and hair problems) of absence of vitamin C in humans comes from defect in hydroxylation of proline residues of collagen (causes scurvy)
Explain PKU
PKU:
Inability to break down phenylalanine into tyrosine
Phe—-> tyrosine by enzyme phenylalanine hydroxylase
causes CNS problems
PKU tested by a blood test in infants
Treatment is diet low in phenylalanine , avoid aspartame
Noticable side affect of PKU is what?
Musty body odor
When would tyrosine become a conditionally essential AA?
In an individual with phenyalanine hydroxylase defeciency
