Urea cycle — Flashcards

Flashcard 1: Where does the urea cycle occur?

Answer: steps in both the cytoplasm and mitochondria

Flashcard 2: urea cycle

Answer: carbomoyl phosphate synthetase I

Flashcard 3: What is the overall purpose of the urea cycle?

Answer: to get NH4+ from amino acid catabolism into an excretable form

Flashcard 4: carbomoyl phosphate synthetase I

Answer: urea cycle

Extra: N-acetylglutamate

Flashcard 5: In which pathway is ornithine transcarbamylase involved?

Answer: urea cycle

Flashcard 6: In which pathways is carbamoyl phosphate involved?

Answer: de novo pyrimidine synthesis; urea cycle

Flashcard 7: ornithine transcarbamylase (OTC) deficiency

Answer:

Extra: inability to eliminate ammoniasomnolence in infantincreased orotic acid in blood and urine, hyperammonemia (and symptoms thereof)same as tx for any hepatic encephalopathy i.e. restrict protein in diet, benzoate or phenylbutyrate, lactulose XR ornithine transcarbamoylase

Flashcard 8: How do levels of serum BUN change with liver dysfunction? _____

Answer: Decreased

Extra:   https://onlinemeded.org/spa/metabolism/urea-cycle/acquire?ref=anki 

Flashcard 9: Hyperammonemia results in excess NH3, which depletes _____, leading to inhibition of the TCA cycle

Answer: α-ketoglutarate

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 10: What is the mode of inheritance of carbamoyl phosphate synthetase I deficiency? _____

Answer: Autosomal recessive

Extra:   https://onlinemeded.org/spa/metabolism/urea-cycle/acquire?ref=anki 

Flashcard 11: Does carbamoyl phosphate synthetase I deficiency present with orotic aciduria? _____

Answer: No

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 12: Arginine may be broken down into _____ and urea via the enzyme arginase

Answer: ornithine

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 13: Does the urea cycle occur in the cytoplasm or mitochondria? _____

Answer: Both :)

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 14: Carbamoyl phosphate synthetase I deficiency presents with _____ NH4+ and _____-ammonemia

Answer: increased

Extra:   https://onlinemeded.org/spa/metabolism?ref=anki 

Flashcard 15: Ornithine transcarbamylase (OTC) deficiency presents with _____ serum glutamine

Answer: increased

Extra:   Watch associated Bootcamp video [https://app.bootcamp.com/med-school/hematology-and-oncology/videos/macrocytic-anemia?index=6] https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 16: Carbamoyl phosphate synthetase I deficiency presents with _____ BUN

Answer: decreased

Extra:   https://onlinemeded.org/spa/metabolism/urea-cycle/acquire?ref=anki 

Flashcard 17: When an amino acid is metabolized, it is broken down into a carbon skeleton and _____ (highly toxic)

Answer: NH3

Extra:    https://onlinemeded.org/spa/metabolism?ref=anki 

Flashcard 18: Ornithine transcarbamylase (OTC) deficiency presents with _____ NH4+ and _____-ammonemia

Answer: increased

Extra:  Watch associated Bootcamp video [https://app.bootcamp.com/med-school/hematology-and-oncology/videos/macrocytic-anemia?index=6] https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 19: Does ornithine transcarbamylase deficiency present with orotic aciduria? _____

Answer: Yes

Extra:   Watch associated Bootcamp video [https://app.bootcamp.com/med-school/hematology-and-oncology/videos/macrocytic-anemia?index=6] https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 20: Disorders of the urea cycle interfere with the body's ability to eliminate _____

Answer: ammonia (NH3)

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 21: Which metabolic pathways require an obligate activator? 1. _____ 2. Urea cycle

Answer: Gluconeogenesis

Extra:   https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 22: _____ cleaves the amino acid arginine into citrulline and nitric oxide

Answer: NO synthase

Extra:  Watch associated Bootcamp video [https://app.bootcamp.com/med-school/cardiology/videos/vasodilation-and-vasoconstriction?index=2] https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 23: The amino acid _____ is essential during periods of positive nitrogen balance

Answer: arginine

Extra:   https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 24: In the liver, glutamate may transfer its NH3 to _____, forming aspartate and α-ketoglutarate

Answer: oxaloacetate

Extra:   https://onlinemeded.org/spa/metabolism?ref=anki 

Flashcard 25: Argininosuccinate may be broken down into _____ and fumarate via the enzyme argininosuccinase

Answer: arginine

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 26: Most excess nitrogen generated by catabolism of amino acids is excreted as _____, which is made in the liver

Answer: urea

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 27: What is the mode of inheritance of ornithine transcarbamylase (OTC) deficiency? _____

Answer: X-linked recessive

Extra:   Watch associated Bootcamp video [https://app.bootcamp.com/med-school/hematology-and-oncology/videos/macrocytic-anemia?index=6] https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 28: Which tissue/organ uses NH3 as its major transport form of NH3? _____

Answer: Intestines (via portal blood)

Extra:   https://onlinemeded.org/spa/metabolism?ref=anki 

Flashcard 29: Does orotic aciduria present with decreased BUN? _____

Answer: No

Extra:  Watch associated Bootcamp video [https://app.bootcamp.com/med-school/hematology-and-oncology/videos/macrocytic-anemia?index=6] https://onlinemeded.org/spa/metabolism?ref=anki 

Flashcard 30: In the first step of the urea cycle, CO2 and NH4+ are combined to form _____ via the enzyme carbamoyl phosphate synthetase I (requires 2 ATP)

Answer: carbamoyl phosphate

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 31: What happens to the ornithine that is formed via the breakdown of arginine (urea cycle)? _____

Answer: It is recycled

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 32: Ornithine transcarbamylase (OTC) deficiency presents with _____ BUN

Answer: decreased

Extra:  Watch associated Bootcamp video [https://app.bootcamp.com/med-school/hematology-and-oncology/videos/macrocytic-anemia?index=6] https://onlinemeded.org/spa/metabolism/urea-cycle/acquire?ref=anki 

Flashcard 33: What is the most common urea cycle disorder? _____

Answer: Ornithine transcarbamylase (OTC) deficiency

Extra:   Watch associated Bootcamp video [https://app.bootcamp.com/med-school/hematology-and-oncology/videos/macrocytic-anemia?index=6] https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 34: Ornithine transcarbamylase (OTC) deficiency often presents within the first few _____ of life but may present later

Answer: days

Extra:  Watch associated Bootcamp video [https://app.bootcamp.com/med-school/hematology-and-oncology/videos/macrocytic-anemia?index=6] https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 35: Urea has two nitrogen molecules, one from _____ and one from aspartate

Answer: NH3

Extra:   https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 36: What is the rate-limiting enzyme of the urea cycle? _____

Answer: Carbamoyl phosphate synthetase I

Extra:    https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 37: In the liver, _____ may transfer a molecule of NH3 to the urea cycle, reforming α-ketoglutarate

Answer: glutamate

Extra:   Watch Cahill Cori Cycles [https://dashboard.sketchy.com/study/medical/courses/medical-biochemistry/units/medical-biochemistry-metabolism/videos/medical-biochemistry-metabolism-amino-acids-and-proteins-the-cahill-and-cori-cycles?utm_source=anki&utm_medium=partnership&utm_campaign=february_update&utm_content=medical] https://onlinemeded.org/spa/dna-to-protein/amino-acids/acquire?ref=anki 

Flashcard 38: Does glutamine cause a change in blood pH? _____

Answer: No

Extra:   https://onlinemeded.org/spa/metabolism?ref=anki 

Flashcard 39: A 2 y/o boy comes with fever, vomiting and sleepiness. - He had several episodes of emesis this morning. -Prior lab testing: Increased blood ammonia levels during these  episodes, & increased orotic acid excretion in urine. -Physical exam: Tachypneic boy who is unresponsive to all stimuli. -Which enzymes is most likely to be deficient in this patient?

Answer: Ornithine transcarbamylase (OTC) due to OTC deficiency which present with high ammonia which causes comma & tachypnea, excess carbamoyl phosphate, which stimulate pyrimidine synthesis. Increased urinary orotic acid.

Flashcard 40: what are the following deficiencies in relation to high circulating NH3 & increase orotic acid in urine? -Carbamoyl phosphate synthetase 1 -Hypoxanthine-guanine phosphoribosyltransferase -N-acetylglutamate synthetase -Ornithine transcarbamylase -Urine monophosphate synthetase

Answer: Carbamoyl phosphate synthetase 1: It will cause an increase in NH3 with low carbamoylphosphate which lead to low orotic acid in urine. -Hypoxanthine-guanine phosphoribosyltransferase: HGPRT deficiency which lead to high uric acid in blood and urine. Urate kidney stone. (Lesch-Nyhan syndrome). -N-Acetylglutamate synthetase: Can't create N-acetylglutamate, thus would cause an increase in NH3 with low carbamoylphosphate, which means high NH3 and low Orotic acid in urine. -Ornithine transcarbamylase: will cause an increase in both NH3 and carbamoyl phosphate which will cause high orotic acid in urine. High NH3 & high orotic acid in urine. -Urine mpnophosphate synthetase: Part of the pyrimidine synthesis pathway. It will an increase in orotic acid but not NH3, because it doesn't involve in the urea cycle.

Flashcard 41: Where in the cell is the carbamoyl phosphate synthetase I enzyme found?_____

Answer: Mitochondria (urea cycle)

Flashcard 42: What is the mode of inheritance of carbamoyl phosphate synthetase I deficiency? _____

Answer: Autosomal recessive

Flashcard 43: What is the mode of inheritance of ornithine transcarbamylase (OTC) deficiency? _____

Answer: X-linked recessive

Flashcard 44: Carbamoyl phosphate synthetase I deficiency presents with _____ BUN

Answer: decreased

Flashcard 45: Most excess nitrogen generated by catabolism of amino acids is excreted as _____, which is made in the liver

Answer: urea

Flashcard 46: What happens to the ornithine that is formed via the breakdown of arginine (urea cycle)? _____

Answer: It is recycled

Flashcard 47: Does ornithine transcarbamylase (OTC) deficiency present with megaloblastic anemia? _____

Answer: No

Flashcard 48: Does ornithine transcarbamylase deficiency present with orotic aciduria? _____

Answer: Yes

Flashcard 49: Carbamoyl phosphate synthetase I deficiency presents with _____ glutamine

Answer: increased

Flashcard 50: Ornithine transcarbamylase (OTC) deficiency presents with _____ BUN

Answer: decreased

Flashcard 51: Where in the cell does the urea cycle begin? _____

Answer: Mitochondria

Flashcard 52: Carbamoyl phosphate synthetase I is regulated via positive feedback by _____

Answer: N-acetylglutamate

Flashcard 53: Which tissue/organ uses NH3 as its major transport form of NH3? _____

Answer: Intestines (via portal blood)

Flashcard 54: In the intestine, NH3 may be produced via the breakdown of the amino acid _____

Answer: glutamine

Flashcard 55: Most disorders of the urea cycle require _____ as an essential amino acid, particularly during episodes of hyperammonemia

Answer: arginine

Flashcard 56: What class of enzymes is used in the transfer of NH3 groups during nitrogen metabolism?_____

Answer: Aminotransferases

Flashcard 57: Part of the treatment for hyperammonemia is limiting _____ in the diet

Answer: protein

Flashcard 58: Urease positive organisms hydrolyze urea to _____, causing urine alkalinization

Answer: ammonia

Flashcard 59: Hyperammonemia results in excess NH3, which depletes _____, leading to inhibition of the TCA cycle

Answer: -ketoglutarate

Flashcard 60: When an amino acid is metabolized, it is broken down into a carbon skeleton and _____ (highly toxic)

Answer: NH3

Flashcard 61: Does orotic aciduria present with decreased BUN? _____

Answer: No

Flashcard 62: Ornithine transcarbamylase (OTC) deficiency presents with _____ serum glutamine

Answer: increased

Flashcard 63: Ornithine transcarbamylase (OTC) deficiency presents with increased _____ acid in the blood and urine

Answer: orotic

Flashcard 64: What other enzyme deficiency presents identically to carbamoyl phosphate synthetase I deficiency? _____

Answer: N-acetylglutamate synthase deficiency

Flashcard 65: Does orotic aciduria present with hyperammonemia?_____

Answer: No

Flashcard 66: What is the major transport form of NH3 in the blood (from most tissues)? _____

Answer: Glutamine

Flashcard 67: Which tissue/organ uses alanine as its major transport form of NH3? _____

Answer: Muscle

Flashcard 68: What is the most common urea cycle disorder? _____

Answer: Ornithine transcarbamylase (OTC) deficiency

Flashcard 69: How do levels of serum BUN change with liver dysfunction? _____

Answer: Decreased

Flashcard 70: Disorders of the urea cycle interfere with the body's ability to eliminate _____

Answer: ammonia (NH3)

Flashcard 71: In the liver, _____ may transfer a molecule of NH3 to the urea cycle, reforming -ketoglutarate

Answer: glutamate

Flashcard 72: What enzyme converts Urea into Ammonia?_____

Answer: Urease

Flashcard 73: The NH3 in the intestine may be transported to the liver in the form of _____ in the portal blood

Answer: NH3

Flashcard 74: Helicobacter pylori is urease-positive, allowing production of ammonia which creates an _____ environment

Answer: alkaline

Flashcard 75: What is the effect of glucagon on urea production?_____

Answer: Increased, secondary to increased gluconeogenesis

Flashcard 76: Does carbamoyl phosphate synthetase I deficiency present with orotic aciduria? _____

Answer: No

Flashcard 77: What is the rate-limiting enzyme of the urea cycle? _____

Answer: Carbamoyl phosphate synthetase I

Flashcard 78: Does the urea cycle occur in the cytoplasm or mitochondria? _____

Answer: Both