Urea Cycle | Purpose, Enzymes & Regulation

The video explains the urea cycle, a crucial process in the liver and kidneys that removes nitrogenous waste by converting ammonia into urea. It details the cycle's steps, including the roles of arginine, ornithine, and citrulline, and highlights the enzymes involved. The energy cost of the cycle is discussed, with a focus on ATP usage and regulation by N-acetylglutamate. The video also covers ammonia sources, such as amino acid metabolism and intestinal bacteria, and emphasizes the cycle's importance in maintaining homeostasis by excreting nitrogenous waste primarily as urea.

Where does the urea cycle primarily occur in the body?

• In the liver

• In the lungs

• In the kidneys

• In the heart

Which enzyme is responsible for converting arginine to ornithine in the urea cycle?

• Carbamoyl phosphate synthetase

• Arginino-succinate synthetase

• Ornithine transcarbamylase

• Arginase

What is the role of carbamoyl phosphate synthetase in the urea cycle?

• It converts ornithine to citrulline

• It synthesizes arginino-succinate

• It combines ammonia and CO2 to form carbamoyl phosphate

• It converts citrulline to arginine

Which molecule acts as an activator for CPS1 in the urea cycle?

• Oxaloacetate

• Fumarate

• N-acetylglutamate

• Aspartate

How many ATP equivalents are used in one turn of the urea cycle?

• Three ATP

• Five ATP

• Two ATP

• Four ATP

Which of the following is a source of ammonia in the body?

• Glutaminase reaction

• Glycolysis

• Beta-oxidation

• Photosynthesis

What percentage of nitrogen waste is excreted as urea?

• 90% to 100%

• 50% to 60%

• 70% to 80%

• 80% to 90%