Which of the following phrases describing the synthesis of amino acids are accurate?

1)The carbon sources for nonessential amino acids synthesis include metabolic pathway intermediates and a-keto acids.

2)The synthesis of alanine from pyruvate, an a-keto acid, involves the oxidation of pyruvate.

3)The carboxyl groups of all the nonessential amino acids are derived from glutamate.

4)Isoleucine is an essential amino acid and is synthesized in the human body by the transamination of a-ketoglutarate.

5)Synthesis of the amino acids involves reduction (that is, the precursor is reduces); its degradation involves oxidation.