MBC - Lecture 41 Word Scramble
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Question | Answer |
Lecture 41 | Nitrogen Incorporation |
Some amino acids are ___, and are derived from ___ sources. | essential, exogenous |
Amino acid catabolism generates ___, a nontoxic carrier of ___ atoms. | urea, nitrogen |
Urea synthesis occurs in the ___. | liver |
Amino acids ___ and ___ will carry amino carry amino acid nitrogen from ___ to the ___. | alanine and glutamine, peripheral tissues to the liver |
___ recovered from deamination of ___ in the liver provides glucose. | Pyruvate, alanine |
Key enzymes involved in nitrogen disposal are: | transaminases, glutamate dehydrogenase, glutaminase |
Humans make ___ non-essential amino acids de novo, and ___ essential amino acids from diet. | 11, 10 |
Urea cycle consists of ___ steps, incorporating nitrogen from ___ and one from ___ into urea. | 4, ammonia, aspartate |
All essential amino acids are derived from corresponding ___. | a-keto acids |
___ supplement is only required during growth. | Arginine |
PVT TIM HALL | Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, Lysine |
Non-essential amino acids are derived by modification of metabolic intermediates from ___ and ___. | glycolysis and TCA cycle |
Modifications involve transfer of ___ and ___. | amino groups and sulfur |
Atmospheric nitrogen is converted to ___ and ___ by nitrogen fixing bacteria and algae. | nitrate and ammonia |
___ is fixed into amino acids and protein. | Ammonia |
Nitrogen balance is the measurement of ___ minus ___. | consumption minus excretion |
If consumption exceeds excretion, then nitrogen balance is ___. | positive (i.e. rapid growth, recovery, etc.) |
If excretion exceeds consumption, then nitrogen balance is ___. | negative (i.e. protein malnutrition, fasting/starvation, essential amino acid deficiency) |
___, ___, and ___ supplements are required in premature infants and liver disease. | Cysteine, tyrosine, and arginine |
___ is first produced in nitrogen excretion, but is toxic. | Ammonia |
___ are the major sources of free ammonia. | Intestinal bacteria |
Small amounts of ___, ___, and ___ are excreted. | uric acid, creatinine, and ammonia |
Majority of ammonia is converted to and excreted as ___. | urea |
BUN (___) measures ___ and ___ function. | blood urea nitrogen, metabolism and renal function |
>___% of nitrogen excreted as ___. | >80%, urea |
Transamination | The major process for moving nitrogen among amino acids |
___ is the major participant in transamination. | Glutamate |
All amino acids except ___ and ___ undergo transamination. | lysine and threonine |
___ (___) is the major cofactor for transaminases. | Pyridoxyl phosphate (PLP) |
Free ammonia in the ___ is incorporated into glutamate by ___. | liver, glutamate dehydrogenase |
Functional form of pyridoxal phosphate, vitamin ___, is covalently linked to various aminotransferases. | vitamin B6 |
Linkage of vitamin B6 is displaced by amino acids ___ or ___. | aspartate or glutamate |
Drugs like ___ and ___ compete for donor amino acid binding, reducing transferase activity. | antituberculosis and isoniazid |
High levels of ___ in blood indicates liver damage. | aminotransferases |
AST/SGOT | Glutamate Aspartate Transferase / Serum Glutamate Oxaloacetate Transaminase |
ALT/SGPT | Glutamate Alanine Transferase / Serum Glutamate Pyruvate Transaminase |
___ is released during transamination of pyridoxal phosphate. | Pyridoxamine |
Key a-keto acid intermediates: | Pyruvate, a-Ketoglutarate, Oxaloacetate |
Oxidative Deamination | Replace amino group with oxygen, free ammonia released |
Dehydratase | Remove water to form an imine, then water is re-added to form keto acid and ammonia |
Oxidative reactions release ___ and require ___ (___) as a co-factor. | free ammonia, flavin mononucleotide(FMN) |
Dehydratase removes water and works on hydroxyamino acids ___ and ___. | serine and threonine |
Glutamate dehydrogenase operates near ___. | equilibrium |
___ reducing equivalents used in amination of a-ketoglutarate. | NADPH |
Glutamate dehydrogenase is a ___ reaction and can ___/___ ammonium to/from glutamate. | reversible, release/incorporate |
Glutamine and asparagine amides deaminated to glutamate and aspartate by ___ and ___. | glutaminase and asparginase |
Three enzymes that fix nitrogen into biomolecules: | Glutamine Dehydrogenase, Glutamine Synthetase, Carbamoyl Phosphate Synthetase |
Amino group of ___ is transferred from a-ketoglutarate during metabolic interconversion to yield ___ and ___. | alanine, pyruvate and glutamate |
Transamination of essential amino acids is ___. | unidirectional |
All transamination reactions involve ___ and ___. | glutamate and a-ketoglutarate |
Liver failure results in impaired ___ excretion (___ occurs). | nitrogen excretion (hyperammonemia) |
Glucose-Alanine Cycle | Elimination of amino acids to the liver and return of carbons to peripheral tissues |
Glutamine is synthesized by ___ to fix nitrogen in muscle for transport to the liver (some to intestine). | glutamine synthetase |
Glutaminase and glutamate dehydrogenase release ___ to the ___ cycle. | nitrogen to the urea cycle |
Urea synthesis occurs in the ___. | liver |
Nitrogen in urea comes from ___ and ___. | ammonia and aspartate |
Carbamoyl Phosphate Synthetase I (CPS I) | Catalyzes formation of carbamoyl phosphate in the mitochondria from ammonia (released from glutamine), 2 ATP, and carbon dioxide |
Deficiency of CPS I leads to: | High blood concentrations of ammonia and related toxicity |
CPS I requires ___ as a co-factor. | N-acetylglutamate |
Carbamoyl Phosphate Synthetase II (CPS II) | Cytosolic form of CPS that does not require N-acetylglutamate |
Ornithine Transcarbamoylase (OTC) | (Transferase) Catalyzes formation of citrulline in the mitochondria from ornithine and carbamoyl phosphate, releasing a Pi |
Deficiency of ornithine transcarbamoylase leads to: | high blood concentrations of ammonia and orotic acid, as carbamoyl is shunted to pyrimidine biosynthesis |
Argininosuccinate Synthetase | (Ligase) Catalyzes formation of argininosuccinate in the cytosol from citrulline and aspartate, requiring an ATP that is cleaved to AMP + PPi |
Deficiency of argininosuccinate synthetase leads to: | high blood concentrations of ammonia and citrulline |
Argininosuccinase | (Lyase) Catalyzes cleavage of argininosuccinate in the cytosol to arginine and fumarate |
Deficiency of argininosuccinase leads to: | high blood concentrations of ammonia and citrulline |
Arginase | (Hydrolase) Catalyzes cleavage of arginine in the cytosol to ornithine and urea |
Deficiency of arginase leads to: | high blood concentrations of ammonia and arginine |
If CPS I is limiting/defective, nitrogen is driven through ___ into the ___ pathway, forming orotic acid detectable in blood and urine. | CPS II into the pyrimidine pathway |
The urea cycle is ___ in times of starvation. | up-regulated |
CPS I is allosterically activated by ___. | N-acetylglutamate |
___ stimulates N-acetylglutamate synthetase. | Arginine |
Ammonia Toxicity | Ammonia encephalopathy/cerebral edema, treat with benzoate/phenylacetate, control nitrogen intake(avoid endogenous protein breakdown), a-keto acid diet |
CPS I/N-Acetylglutamate Deficiency | Hyperammonemia/encephalopathy/respiratory alkalosis, autosomal recessive, fatal in infants with possible delayed onset |
OTC Deficiency | Mental Retardation/Death (NH3 accumulation), X-linked, most common urea cycle defect |
Arginosuccinate Synthetase Deficiency | Severe hyperammonemia/increased citrulline in blood and urine, autosomal recessive, treat with low protein and arginine supplements |
Therapy for partially defective urea cycle involves: | limit protein intake, remove excessive NH3 with compounds (benzoate and phenyl acetate) that covalently bind and are excreted, replace missing urea cycle intermediates, liver transplant |
Majority of protein breakdown occurs in ___. | skeletal muscle |
Urea is transported from the ___ to the ___. | liver to the kidney |
The kidney excretes ___, ___, and ___. | ammonia, glutamate, and urea |
Fumarate can be used in formation of ___ and __, or the reformation of ___. | ATP and glucose, aspartate |
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