Question

Normally the liver helps to maintain low blood ammonia levels by the glutamine cycle of which glutaminase is an important component. Glutaminase A. is found in the same liver compartment as the urea cycle enzymes. B. requires ATP for the reaction it catalyzes. C. is the sole source of ammonia for urea synthesis. D. is more active in liver in acidosis. E. provides the product that combines with ornithine in the urea cycle.

Short answer

A) is found in the same liver compartment as the urea cycle enzymes. B) requires ATP for the reaction it catalyzes. C) is the sole source of ammonia for urea synthesis. D) is more active in liver in acidosis. E) provides the product that combines with ornithine in the urea cycle. Answer: A, D

Step-by-step solution

Analyze Option A.

Let's look at the first option: "is found in the same liver compartment as the urea cycle enzymes." The urea cycle enzymes are found in the liver, specifically in the mitochondria and cytosol. Glutaminase, on the other hand, is an enzyme that breaks down glutamine to release ammonia, which is an essential component of the urea cycle. So, this statement is true, as glutaminase is indeed found in the same liver compartment as the urea cycle enzymes.

Analyze Option B.

Now, let's look at Option B: "requires ATP for the reaction it catalyzes." Glutaminase catalyzes the hydrolysis of glutamine to glutamate and ammonia. This reaction does not require ATP input. Therefore, this statement is false.

Analyze Option C.

Option C states that "is the sole source of ammonia for urea synthesis." While glutaminase is one source of ammonia for urea synthesis, it is not the only source. Other amino acids can also generate ammonia as a product of their catabolic reactions. Thus, this statement is false.

Analyze Option D.

Option D states that "is more active in liver in acidosis." Acidosis is a condition where the blood becomes acidic, leading to decreased blood pH levels. When the body is in a state of acidosis, the liver increases the production of ammonia to help buffer the blood pH level. This increased ammonia production is primarily achieved through increased glutaminase activity, so this statement is true.

Analyze Option E.

Finally, Option E suggests that glutaminase "provides the product that combines with ornithine in the urea cycle." The product of glutaminase is ammonia and glutamate, but the molecule that combines with ornithine in the urea cycle is carbamoyl phosphate (which is formed from the reaction of ammonia with bicarbonate and ATP). Therefore, this statement is false.

Conclusion

After analyzing all the options individually, we can conclude that Options A and D are correct statements. Glutaminase is found in the same liver compartment as the urea cycle enzymes and is more active in the liver during acidosis.