BioChem 1430 ch. 30 (Well-Enlightened)

Which of the following amino acids is glucogenic? correct answers A) asparagine B) methionine C) valine D) lysine Correct Response E) A, B, and C In the urea cycle, free NH4+ is coupled with carboxyphosphate to form: correct answers carbamic acid. In the urea cycle, the carbon skeleton of aspartate is preserved as: correct answers fumarate. Surplus amino acids are correct answers used as metabolic fuel. Three enzymes of the urea cycle require ATP, but when counting high-transfer-potential phosphoryl groups spent, the number is four. Explain this apparent discrepancy. correct answers Argininosuccinate synthetase is driven by the cleavage of ATP into AMP and pyrophosphate and by the subsequent hydrolysis of pyrophosphate. Metabolic pathways are said to be variations on a theme. Which of the following would accurately illustrate this statement? correct answers Cleavages of aromatic rings in amino acids are catalyzed by oxygenases. Which amino acids supply carbons for eventual entry into metabolism as succinyl CoA? correct answers methionine, isoleucine, valine Which amino acids can be directly deaminated to produce NH4+? correct answers serine and threonine Individuals with phenylketonuria can ameliorate the symptoms by consuming a diet low in phenylalanine. Would the same strategy (a diet low in one amino acid) work for individuals with citrullinemia? correct answers No, citrullinema is due to a deficiency of argininosuccinase, an enzyme that all amino acids ultimately utilize for nitrogen disposal. As shown in Chapter 28, excess alcohol consumption not only makes you overweight, it can also lead to ammonia poisoning. How is alcohol metabolism linked to increased levels of blood ammonia? correct answers Excess alcohol consumption can cause liver damage, the primary site of urea formation. Loss of liver function can lead to increases of ammonia in the blood. Which amino acid is a metabolite in the urea cycle, but is not used as a building block of proteins? correct answers A) ornithine B) citrulline