Across
1
Substance with pH below 7
4
Biological catalyst
5
Curved glass that refracts light
8
Nerve cell in the brain
12
Basic unit of life
Down
2
Compound containing oxygen
3
Element found in all living things
6
Absolute temperature scale unit
7
Center of an atom or cell
9
Tissue that contracts for movement
10
Naturally occurring inorganic solid
11
Force that attracts objects together