Urea Cycle And Detoxification

Question 1

What is the urea cycle important?

Answer 1

It removes excess ammonia from the circulatory system and converts it to urea and excreted in the urine

Question 2

Describe the process of detoxification of ammonia

Answer 2

1. Ammonia is converted to carbamoyl phosphate by carbamoyl phosphate synthase 1
2. Carbamoyl phosphate reacts with omithine to form citrulline catalyzed by ornithine transcarbmylase
3. Citrulline is relocated to the cytoplasm by ORNT-1 transporter
4. Citrulline reacts with aspartate to form argininosuccinate catalyzed by argininosuccinate synthetase
5. Argininosuccinate is cleaved into fumarate and arginine by argininosuccinase
6. Arginine is lysed into omithine and urea by arginase

Question 3

What are the products of detoxification?

Answer 3

Urea, fumarate, ADP, AMP, inorganic phosphate, pyrophosphate, water

Question 4

How is the urea cycle regulated?

Answer 4

Substrate concentrations and N-acetylglutamic acid

Question 5

What happens to carbon skeletons after use?

Answer 5

1. Converted to glucose precursors for gluconeogenesis
2. Converted to ketone bodies for ketogenesis
3. Oxidized through TCA cycle and made into ATP during oxidation

Question 6

How is urea used in ruminants? Why?

Answer 6

Urea is recycled back to the rumen where microbes use urease to hydrolyze urea back to ammonia and CO2
They utilize the non-protein nitrogen sources and contribute to overall protein intake