Question

Haemoglobin in teleosts is :

• A. Monomeric
• B. Dimeric
• C. Trimeric
• D. Tetrameric

Hint:

Nearly all jawed vertebrates, including teleost fishes, possess tetrameric (\(\alpha_2\beta_2\)) hemoglobins to facilitate cooperative oxygen binding and physiological adaptations like the Root effect.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Hemoglobin is the primary respiratory pigment in the blood of vertebrates, responsible for binding oxygen at respiratory surfaces and transporting it to tissues.
Its molecular structure can vary across different evolutionary groups.

Step 2: Detailed Explanation:
In typical teleost (bony) fishes, hemoglobin is a tetrameric protein.
This means it is composed of four individual polypeptide subunits (chains) bound together, typically consisting of two \(\alpha\)-like chains and two \(\beta\)-like chains, similar to mammalian hemoglobin.
This tetrameric structure (\(\alpha_2\beta_2\)) is highly functional as it allows for cooperative binding of oxygen (allosteric regulation), where the binding of one oxygen molecule facilitates the binding of subsequent molecules.
It also enables physiological mechanisms like the Bohr effect and Root effect, which are essential for unloading oxygen under acidic conditions, especially into the swim bladder and the retina.
Let us note that:
- Monomeric hemoglobins (single-chain) are found in primitive jawless vertebrates like lampreys and hagfishes (Cyclostomes).
- Dimeric and trimeric structures are not standard for functional vertebrate hemoglobins.

Step 4: Final Answer:
Therefore, hemoglobin in teleosts is Tetrameric.