Question

______ protein fraction of egg yolk is water soluble.

• A. Livetin
• B. Ovalbumin
• C. Globulin
• D. Covalbumin

Hint:

Egg yolk proteins are broadly divided into insoluble granules (lipovitellin, phosvitin) and soluble plasma (lipovitellenin, livetins). Livetins are the water-soluble non-lipid-bearing globular proteins of the yolk.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Egg yolk is a complex, concentrated lipid-protein emulsion consisting of approximately 50% water, 16% protein, and 30% lipid.
The proteins in egg yolk are structurally divided into plasma (water-soluble fraction) and granules (water-insoluble fraction).

Step 2: Detailed Explation:
To isolate the proteins of egg yolk, centrifugation is typically used to separate the yolk into granules and supertant plasma.
- Granules: Contain insoluble lipoprotein complexes such as lipovitellin (high-density lipoprotein) and phosvitin (a highly phosphorylated phosphoprotein).
- Plasma: Contains the soluble fractions.
The main water-soluble protein fraction in the plasma is called livetin.
Livetins are globular proteins that account for approximately 10% to 20% of the total yolk proteins and are soluble in water.
They are classified into \(\alpha\)-, \(\beta\)-, and \(\gamma\)-livetins, which correspond chemically to serum albumin, glycoprotein, and \(\gamma\)-globulin (immunoglobulin IgY) of hen's blood, respectively.
On the other hand, ovalbumin, globulin, and colbumin (ovotransferrin) are major proteins found in egg white (albumen), not in egg yolk.

Step 3: Fil Answer:
Livetin is the principal water-soluble protein fraction present in egg yolk.
Hence, the correct option is (A).