17 Questions
In which clinical condition is ammonia level within normal range, while urea level increases in the blood?
Renal failure
What is the consequence of ammonia accumulation in the brain on the TCA cycle?
Debilitation of energy production
What is the role of glutamate dehydrogenase enzyme in the brain?
Reacting ammonia with α-ketoglutarate acid to form glutamate
What is the consequence of collateral circulation in liver cirrhosis?
Ammonia entry into systemic circulation
What is the primary source of energy for the brain?
TCA cycle
What is the primary location where ammonia is converted into non-toxic urea?
Liver
Which enzyme requires N-acetyl glutamate as an activator in the urea cycle?
Carbamoyl phosphate synthase I
What is the immediate product of the reaction between CO2 and ammonia in the urea cycle?
Carbamoyl phosphate
What is the rate-limiting enzyme in the urea cycle that is allosterically activated by N-acetyl glutamate?
Carbamoyl phosphate synthase 1
What is a potential cause of hyperammonemia?
Deficiency in carbamoyl phosphate synthase I
What is the source of CO2 needed for the first step of the urea cycle?
Citric acid cycle (TCA)
What is the TCA cycle intermediate produced in the urea cycle after the deamination of glutamate?
a-Ketoglutarate
What is the result of a defect in the ornithine transporter in the urea cycle?
All of the above
How many ATP molecules are required for the first step of the urea cycle, catalyzed by carbamoyl phosphate synthase I?
2
What is the role of N-acetyl glutamate in the urea cycle?
Allosteric activator of carbamoyl phosphate synthase 1
What is the consequence of liver cell dysfunction on the urea cycle?
Acquired hyperammonemia
What is the relationship between the urea cycle and the TCA cycle?
The TCA cycle produces CO2 and oxaloacetate for the urea cycle
This quiz covers the regulation of the urea cycle, including the role of carbamoyl phosphate synthase 1 as the rate-limiting enzyme and the activation by N-acetyl glutamate, which is promoted by a high protein diet rich in arginine. Understand the process of arginine cleavage and the excretion of urea. Test your knowledge of the urea cycle and its regulation.
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