(Some Questions denote their format. All questions are answered) 1. The metabolic process of urea synthesis occurs primarily in the ________. A) liver B) kidneys C) lungs D) small intestine Answer: A) liver. Urea is synthesized in the liver through the urea cycle. 2. The main function of urea in the body is to ___________. A) serve as a waste product for nitrogen excretion B) increase ATP production C) regulate blood sugar levels D) facilitate amino acid synthesis Answer: A) serve as a waste product for nitrogen excretion. Urea is formed in the liver as a way to remove excess nitrogen from the body. 3. Which of the following enzymes is involved in the first step of the urea cycle? A) Arginase B) Carbamoyl phosphate synthetase I C) Ornithine transcarbamylase D) Argininosuccinate synthetase Answer: B) Carbamoyl phosphate synthetase I. This enzyme catalyzes the reaction that converts ammonia and bicarbonate into carbamoyl phosphate. 4. True or False: The urea cycle is the primary pathway for nitrogen excretion in humans.