. "The chemical reactions and pathways resulting in the formation of any of the vitamin A compounds, retinol, retinal (retinaldehyde) and retinoic acid. Animals cannot synthesize vitamin A de novo, but form it through oxidative cleavage of carotenoids." . . . . "vitamin A biosynthetic process" . "vitamin A anabolism" . "vitamin A biosynthesis" . "vitamin A formation" . "vitamin A synthesis" . . . .