bone matrix contains all the following but ?

Question

bone matrix contains all the following but sodium, calcium, phosphate, collagen fibers

Answer 1

Sodium is not part of the bone matrix…

Collagen is a protein that forms the sturdy but flexible framework for the bones. A mineral compound made of Calcium phosphate--also known as hydroxyapitite--is the what gives the bone its rigidity and hardness. 

Answer 2

Thanks Michael...

 

The bone matrix is comprised of collagen fibers in a cross linked formation.  The matrix itself contains both calcium and phosphate reserves for use in the body's maintenance of homeostasis.

 

Therefore, sodium would be the "odd man out".