When muscle proteins undergo catabolism in skeletal muscle during a fast, what are the fates of the amino acids?
a. Amino acid carbon skeletons undergo oxidation to compounds that can enter the citric acid cycle.
b. Free amino acids undergo activation and ß oxidation to form acetyl-CoA and NADH.
c. The amino acids are precursors in the biosynthesis of nucleotides and hormones in the liver.
d. The process of gluconeogenesis converts glucogenic amino acid carbon skeletons to glucose for the brain.
e. The urea cycle converts the amino acid carbon skeletons from skeletal muscle to the excretory product urea.