Indicate whether each of the following statements is true or false, and briefly explain your answer.
(a) In general, the metabolic oxidation of protein in mammals is less efficient, in terms of energy conserved, than the metabolic oxidation of carbohydrate or fat.
(b) Given that the nitrogen of glutamate can be redistributed by transamination, glutamate should be a good supplement for nutritionally poor proteins.
(c) Arginine is a nonessential amino acid for mammals because the enzymes of arginine synthesis are abundant in liver.
(d) Alanine is an essential amino acid because it is a constituent of every protein.