Answer: Iron (Fe 2+ ).
- A Iron (Fe<sup>2+</sup>)
- B Copper (Cu<sup>2+</sup>)
- C Zinc (Zn<sup>2+</sup>)
- D Magnesium (Mg<sup>2+</sup>)
Correct answer: A. Iron (Fe<sup>2+</sup>)
Explanation: Haemoglobin contains iron (Fe<sup>2+</sup>) in its haem group, which binds oxygen.
Two amino acids join via a condensation reaction: the carboxyl -OH of one and an amine -H of the other are eliminated as water, leaving a peptide bond (-CO-NH-) linking them into a dipeptide; repeating this builds a full protein chain.
Concept context
The chemistry of life: carbohydrates, proteins, lipids, nucleic acids, enzymes, and vitamins. Understand their structures, classification, and biological functions. Highly relevant for NEET and Class 12 board exams.