Difficulty: Easy
Correct Answer: Calcium phosphate
Explanation:
Introduction / Context:
Bones and teeth are the hard supporting and biting structures of the human body. They must be strong enough to withstand mechanical stress yet light enough to allow movement. This strength comes from a combination of a protein framework and mineral deposits. Many students know that calcium is important for bones and teeth, but fewer can correctly identify which specific calcium compound forms the main mineral part. This question tests your understanding of basic human physiology and inorganic chemistry by asking which calcium salt is the major component of bones and teeth.
Given Data / Assumptions:
Concept / Approach:
In biology and chemistry, it is well known that the mineral part of bones and teeth is largely made up of a crystalline form of calcium phosphate called hydroxyapatite. This mineral is deposited on a collagen protein matrix to form strong but slightly flexible tissue. Calcium carbonate does occur in some shells and other organisms but is not the main mineral in human bones. Calcium nitrate and calcium sulphate have other uses and are not primary skeletal minerals. The correct approach is to recall which calcium compound forms hydroxyapatite and matches the composition of bones and teeth.
Step-by-Step Solution:
Step 1: Recall that bones are made of an organic matrix rich in collagen plus inorganic mineral salts.
Step 2: Remember that the dominant mineral deposited in this matrix is hydroxyapatite, a crystalline form of calcium phosphate.
Step 3: Recognise that calcium carbonate is common in seashells and some invertebrate skeletons but not the main mineral in human bones.
Step 4: Note that calcium nitrate and calcium sulphate are industrial and agricultural salts, not structural components of human bone tissue.
Step 5: Conclude that the option calcium phosphate correctly represents the main chemical component of bones and teeth.
Verification / Alternative check:
To verify, think of any basic anatomy or physiology textbook diagram showing bone structure. It usually labels hydroxyapatite as Ca10(PO4)6(OH)2 and describes it as a calcium phosphate mineral. Dental science texts similarly describe tooth enamel and dentin as rich in calcium phosphate crystals. In contrast, calcium carbonate is clearly identified with structures like oyster shells or eggshells. Since the question asks specifically about bones and teeth and not shells, this independent knowledge confirms that calcium phosphate is the main component and supports our choice.
Why Other Options Are Wrong:
Calcium carbonate is not the primary mineral in human bones and teeth. It is more characteristic of shells and some external skeletons, so this option is incorrect in this context.
Calcium nitrate is a soluble salt often used in fertilisers and laboratory solutions. It does not form the hard structural matrix of bones or teeth, so this option is wrong.
Calcium sulphate is used as plaster of Paris in medicine and construction, but it is not the main mineral deposited in the human skeleton, making this choice incorrect as well.
Common Pitfalls:
A frequent mistake is to see any option with the word calcium and assume it must be correct, without considering the accompanying anion such as phosphate, carbonate, nitrate, or sulphate. Another pitfall comes from confusion between human skeletons and shells, leading students to pick calcium carbonate. Some learners may also simply choose the compound they have heard more often in everyday life rather than the one they remember from biology class. To avoid these errors, connect the term hydroxyapatite with calcium phosphate whenever you think about bones and teeth.
Final Answer:
The main chemical component of human bones and teeth is calcium phosphate.
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