Q.25 Myoglobin is a globular protein, which is made up of
1. 159
2.153
3.160
4.170
Myoglobin Amino Acids: Correct Count Revealed (MCQ Answer)
Myoglobin, a key oxygen-storage protein in muscles, consists of a specific number of amino acids in its human polypeptide chain. The correct answer to this multiple-choice question is option 1: 159 amino acids.
Correct Answer
Human myoglobin is a monomeric globular protein encoded by the MB gene, forming a single polypeptide chain of exactly 159 amino acids. This chain folds into eight α-helices (A-H) that create a compact structure housing a heme group for oxygen binding. The 159-residue count is standard in most references, though minor isoforms exist; the canonical form matches this for exam contexts.
Option Analysis
Compare all options with structural details:
| Option | Amino Acids | Explanation |
|---|---|---|
| 1. 159 | 159 | Correct. Standard human myoglobin polypeptide; 75% α-helical with heme pocket. |
| 2. 153 | 153 | Close but incorrect; some sources approximate or cite sperm whale myoglobin (153 residues). Human version has 154-159. |
| 3. 160 | 160 | Incorrect approximation; exceeds verified chain length. |
| 4. 170 | 170 | Wrong; confuses with larger globins like hemoglobin subunits (~141-146 residues). |
Myoglobin Structure Overview
Myoglobin’s globular form is hydrophilic on the surface and hydrophobic inside, aiding solubility and stability. It stores oxygen in muscle mitochondria, differing from hemoglobin’s transport role. For exams, memorize 159 as the human count to distinguish from animal variants.
