Question

The porphyrin ring (tetrapyrrole structure) is NOT found in functional

• A. chlorophyll
• B. hemoglobin
• C. hemocyanin
• D. leghemoglobin

Hint:

Porphyrin-based structures include chlorophyll (Mg-porphyrin) and hemoproteins like hemoglobin and leghemoglobin (Fe-porphyrin). Hemocyanin is unique—it uses Cu without porphyrin.

Answer 1

The Correct Option is C

Step 1: Understanding porphyrin ring (tetrapyrrole).
A porphyrin ring is a cyclic tetrapyrrole structure that binds metal ions (like Fe or Mg) at its center. This structure is critical for many biological pigments and proteins.
Step 2: Evaluate each option.
- Option (A) Chlorophyll: Contains a porphyrin ring with central Mg\(^{2+}\), crucial for photosynthesis.
- Option (B) Hemoglobin: Contains heme, a porphyrin ring with central Fe\(^{2+}\), essential for oxygen transport.
- Option (C) Hemocyanin: Found in mollusks and arthropods; uses Cu ions bound to histidine residues. It does not contain a porphyrin ring.
- Option (D) Leghemoglobin: Similar to hemoglobin, contains a heme group (iron–porphyrin complex).
Step 3: Conclusion.
Among the given options, only hemocyanin does not contain a porphyrin ring.
Final Answer: \[ \boxed{\text{Hemocyanin is the protein that lacks a porphyrin (tetrapyrrole) ring.}} \]