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Questions and Answers
Which organ is the only site for urea formation in the body?
Which organ is the only site for urea formation in the body?
In which organelle do the first two reactions of the urea cycle occur?
In which organelle do the first two reactions of the urea cycle occur?
Which molecule is used to provide phosphate in the synthesis of carbamoylphosphate in the urea cycle?
Which molecule is used to provide phosphate in the synthesis of carbamoylphosphate in the urea cycle?
From which compound is the first nitrogen atom in urea derived in the urea cycle?
From which compound is the first nitrogen atom in urea derived in the urea cycle?
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What is the diagnostic importance of blood urea measurement?
What is the diagnostic importance of blood urea measurement?
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How many ATP molecules and high-energy phosphate bonds are utilized in the urea cycle reactions?
How many ATP molecules and high-energy phosphate bonds are utilized in the urea cycle reactions?
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What is the key enzyme of the urea cycle?
What is the key enzyme of the urea cycle?
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What stimulates the synthesis of N-acetylglutamate, an allosteric activator of carbamoyl phosphate synthetase I?
What stimulates the synthesis of N-acetylglutamate, an allosteric activator of carbamoyl phosphate synthetase I?
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Which of the following may cause coma and death due to high concentrations of ammonia?
Which of the following may cause coma and death due to high concentrations of ammonia?
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Which enzyme deficiency leads to hyperammonemia type II, an X-linked inherited disease?
Which enzyme deficiency leads to hyperammonemia type II, an X-linked inherited disease?
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What is the treatment for argininemia, a condition caused by deficiency of arginase?
What is the treatment for argininemia, a condition caused by deficiency of arginase?
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7
7
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What is a characteristic symptom of hyperammonemia?
What is a characteristic symptom of hyperammonemia?
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What may stimulate the excretion of citrulline, thereby alleviating citrullinemia?
What may stimulate the excretion of citrulline, thereby alleviating citrullinemia?
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What is the main cause of inherited hyperammonemia?
What is the main cause of inherited hyperammonemia?
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Study Notes
Urea Cycle
- The liver is the only site for urea formation in the body.
Urea Cycle Reactions
- The first two reactions of the urea cycle occur in the mitochondrial matrix.
- The molecule ATP is used to provide phosphate in the synthesis of carbamoylphosphate in the urea cycle.
Nitrogen Source
- The first nitrogen atom in urea is derived from ammonia (NH3) in the urea cycle.
Blood Urea Measurement
- Blood urea measurement is diagnostically important.
Energy Requirements
- 3 ATP molecules and 2 high-energy phosphate bonds are utilized in the urea cycle reactions.
Key Enzyme
- Carbamoyl phosphate synthetase I is the key enzyme of the urea cycle.
Regulation of Carbamoyl Phosphate Synthetase I
- N-acetylglutamate, an allosteric activator of carbamoyl phosphate synthetase I, is synthesized in response to arginine, ornithine, or glucagon.
Hyperammonemia
- High concentrations of ammonia can cause coma and death.
- Hyperammonemia type II, an X-linked inherited disease, is caused by a deficiency of ornithine transcarbamylase.
- Argininemia, a condition caused by a deficiency of arginase, can be treated with a low-protein diet and supplementation with citrulline and arginine.
- A characteristic symptom of hyperammonemia is vomiting.
- The excretion of citrulline can be stimulated by supplementation with citrulline, which alleviates citrullinemia.
- Inherited deficiencies of enzymes involved in the urea cycle are the main cause of inherited hyperammonemia.
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Description
Test your knowledge on urea cycle and blood urea levels with this quiz. Learn about the site of urea formation, diagnostic importance of blood urea, and related concepts.
