The inorganic matter that makes up the matrix of bone is mainly calcium phosphate in the form of hydroxyapatite crystals (often written simply as “calcium phosphate salts”).

Quick Scoop

  • Bone matrix has:
    • Organic part : mostly collagen fibers and ground substance, which give flexibility.
* **Inorganic part** : mainly calcium phosphate (hydroxyapatite) plus smaller amounts of other mineral ions.
  • So, for a multiple‑choice style question, the correct option for “part of the inorganic matter” would be calcium phosphate (calcium phosphate salt / hydroxyapatite) , not collagen, proteoglycans, or glycoproteins, which are organic.
If your choices include “Calcium phosphate salt,” that is the answer.
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