Yes, PLASM is a Scrabble word!

Letter values in Scrabble US: P 3, L 1, A 1, S 1, M 3.

Is it a valid word?

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

the protoplasm of the germ cells that contains chromosomes and genes
the colorless watery fluid of the blood and lymph that contains no cells, but in which the blood cells (erythrocytes, leukocytes, and thrombocytes) are suspended

Also: germ plasm, blood plasma.