Biochemistry: Detoxification of Ammonia and Urea Cycle Quiz

Which enzyme catalyzes the formation of carbamoyl phosphate for urea synthesis, using NH4+?

What is the reference level of urea in the blood plasma?

Where is urea produced?

What is the main α-ketoacid that serves as an NH2 group acceptor during transamination to form glutamate?

What is the role of glutamine in the synthesis of carbamoyl phosphate?

Which of the following is NOT a source of ammonium for the urea cycle?

What happens when the concentration of ammonia in the blood exceeds 400 μM?

Which of the following represents the conversion of free ammonia into a nontoxic transport form?

What is the main role of the urea cycle in ammonia detoxification?

Which enzyme catalyzes the conversion of glutamine to glutamate in the process of ammonia detoxification?

Urea Cycle Enzymes and Processes

Carbamoyl phosphate is formed from ammonium ion (NH4+) by the enzyme carbamoyl phosphate synthetase I.
Glutamine plays a significant role by donating an amino group to form carbamoyl phosphate, particularly in tissues requiring rapid detoxification of ammonia.

Urea Production and Levels

Urea is produced primarily in the liver, a key organ in nitrogen metabolism.
Normal reference levels of urea in blood plasma typically range from 2.5 to 7.5 mM.

Ammonium Sources for the Urea Cycle

Not all sources contribute to the urea cycle; lactate, for instance, is NOT a source of ammonium.
The main α-ketoacid that accepts the amino group during transamination to produce glutamate is α-ketoglutarate.

Ammonia Detoxification Mechanisms

If ammonia concentration in the blood exceeds 400 μM, it can lead to toxic effects, including neurological damage and hepatic encephalopathy.
The conversion of free ammonia to a nontoxic transport form is primarily represented by the synthesis of glutamine from glutamate.

Summary of Urea Cycle Function

The main role of the urea cycle is to detoxify ammonia, converting it into urea for safe excretion.
The enzyme that catalyzes the conversion of glutamine to glutamate during ammonia detoxification is glutaminase.

Test your knowledge on the detoxification of ammonia, the urea cycle, and the catabolism of the carbon skeletons of amino acids in biochemistry. This quiz covers topics such as the metabolism of Phe, Tyr, and Met, the role of folic acid, biosynthesis of creatine and phosphocreatine, and biosynthesis of nonessential amino acids.