Across
1
Biological catalyst
4
Center of an atom or cell
5
Precious yellow metallic element
7
Infectious microscopic agent
8
Unit of force
9
Tissue that contracts for movement
Down
2
Molten rock beneath Earth surface
3
Mass per unit volume
4
Nerve cell in the brain
6
Compound containing oxygen
9
Naturally occurring inorganic solid
10
Measure of matter in an object
11
Curved glass that refracts light