G Which two of the statements describing the synthesis of amino acids are accurate? Synthesis of the amino acid alanine involves reduction, that is, the precursor is reduced; its degradation involves oxidation. Valine is an essential amino acid and is synthesized in the human body by the transamination of α‑ketoglutarate. The carboxyl groups of all the nonessential amino acids are derived from glutamate. The synthesis of alanine from pyruvate, an α‑keto acid, involves the oxidation of pyruvate. The carbon sources for nonessential amino acid synthesis include metabolic pathway intermediates and α‑keto acids.