Yes, AUTOTROPHIC is a Scrabble word!

Letter values in Scrabble US: A 1, U 1, T 1, O 1, T 1, R 1, O 1, P 3, H 4, I 1, C 3.

Is it a valid word?

AUTOTROPHIC is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

of or relating to organisms (as green plants) that can make complex organic nutritive compounds from simple inorganic sources by photosynthesis

Not playable in Scrabble US: AUTOPHYTIC.