Question

Hydroxyapatite constitutes
I. Bone
II. Cartilage
III. Teeth
IV. Both A and C

Answer 1

Hint: Hydroxyapatite is a very hard substance. Therefore, it occurs naturally in the hard parts of the body, mainly the components that form the hard parts of the skeleton of our body.

Step by step answer:The hydroxyapatite is also known as the Hydroxylapatite. It is the naturally occurring mineral form of calcium apatite. It is given by the chemical formula.
Bone – The cells making up the bone are known as the Osteocyte cells. The bone is made up of and. In other words, by volume and by weight of the human bone is bone mineral. The bone mineral is the modified form of the hydroxyapatite. The crystals of hydroxyapatite are found interspersed in the matrix of the collagen protein. Hence, hydroxyapatite makes about the mass of the bone.
Cartilage – The cells making up the cartilage are known as the chondrocyte cells. The cartilage is made up of but it has less Calcium. Due to this reason, the cartilage is softer as compared to bones.
Teeth – The teeth are made up of calcium phosphate. The dental enamel and the dentine are mostly made up of the hydroxyapatite. The mass of the enamel and the dentine is made up of the hydroxyapatite. This makes them very hard. Also, their organic part is very low so their demineralization is difficult. Thus, the Hydroxyapatite constitutes both Bones and Teeth.
Hence option IV is correct.

Note: Apart from the bones and teeth, hydroxyapatite is also found as crystals of small calcifications, within the Pineal gland. This is known as corpora arenacea or the ‘brain sand’.