Which of the following is the main component of bone and teeth?

Appeared in: NHM UP Staff Nurse - 2017

Explanation

Calcium and phosphate are the two primary minerals that combine to form hydroxyapatite crystals [Ca₁₀(PO₄)₆(OH)₂].
Hydroxyapatite is the main inorganic constituent of bone and teeth, providing them with rigidity and compressional strength.
Approximately 80% of the body's total phosphorus is stored in the skeleton, bound to calcium, highlighting its role as the primary mineral component.
Tooth enamel is the most mineralized substance in the body, containing about 96% hydroxyapatite by weight, which makes it extremely hard and durable.

Option A: Calcium carbonate is only a minor component of the mineral matrix of bone and is not the main structural element.
Option C: Calcium sulphate (gypsum/plaster of Paris) is not a biological component of human bone or teeth.
Option D: Calcium nitrate is a highly water-soluble salt that has no structural role in the human body.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mineral composition of bone and teeth as background academic context rather than a clinical decision trigger.
Understanding that bone is primarily calcium phosphate is fundamental for managing metabolic bone diseases. For instance, in osteoporosis, there is a loss of this mineral matrix, leading to increased fracture risk.
Nurses play a key role in educating patients about the importance of adequate dietary intake of both calcium and phosphorus for maintaining bone health and preventing conditions like rickets (in children) and osteomalacia (in adults), which are caused by defective mineralization.
This knowledge is crucial for interpreting lab results. Serum calcium and phosphate levels are tightly regulated, and imbalances can indicate underlying diseases like parathyroid disorders or kidney failure.

How to Approach the Question

This is a factual recall question based on fundamental concepts in anatomy and physiology.
Identify the keywords in the question stem: 'main component', 'bone', and 'teeth'.
The question asks for the primary chemical compound that makes up these hard tissues.
Evaluate the options provided. All are salts of calcium, so the task is to identify the correct anion (the non-calcium part).
Recall that bone mineral is a complex of calcium and phosphate, known as hydroxyapatite.
Select 'Calcium phosphate' as it accurately represents this primary structural mineral.

Concept Tested & Keywords

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E6 Biochemistry U Satyanarayana— Part 2 (pp 421-820 of 840) pp. 26-28, 41-43

Practise the full NHM UP Staff Nurse - 2017

Attempt every question from this paper in a timed mock, then review the full solution for each one.