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Block 6-Urea

Block 6- Urea cycle

QuestionAnswer
Where is urea synthesized? liver
What is the structure of urea? 2 amino groups attached to a central carbonyl group
Where do the parts of urea come from? Carbonyl derived from CO2, 1 N-atom from aspartate (asp) the other from ammonium
Where does Urea synthesis begin and end within the cell? Mitochondria to start, cytoplasm to finish
How much energy is required to run the urea cycle? 4 ATPs
What is the crucial, rate limiting first enzyme for urea synthesis (found in mitochondria)? carbamoyl phosphate
What is the second enzyme of the urea cycle? Also rate limiting Ornithine transcarbamoylase condenses carbamoyl phosphate with ornithine to form citruline
The most common genetic defiencies in urea cycle are associated with what? the two enzymes: carbamoyl phosphate & ornithine transcarbamoylase
What does arginase do in the urea cycle? Where? cleaves arginine into urea and ornithine (which is recycled.
Where does apspartate occur in the urea cycle? It enters in the cytoplasm to convert citrulline to argininosuccinate which cleaves to form fumarate and arginine by a lyase.
Is all the arginine required available via urea synthesis? No, most comes from diet.
What happens with CPS-1 and Ornithine transcarbamoylase deficiency? Hyperammonenemia; Decrease in BUN (Blood Urea Nitrogen, Cerebral edema;lethargy, convulsion, coma, death
What is the difference between Aspartate and Fumarate? fumarate does not have the amino group
Where does fumarate go following the urea cycle? It can enter the TCA for energy or gluconeogenesis
Where does urea go from the kidney? Transported by blood to the kidney
What is the famous phrase regarding the urea cycle? Better to be pissed off, than pissed on
Created by: El Diablo