Question

In oviparous fishes, the precursors of yolk proteins (vitellogenins) are synthesized in which organ?

• A. Ovary
• B. Intestine
• C. Liver
• D. Gallbladder

Hint:

Think of the liver as the "manufacturing plant" for yolk precursors, and the ovary as the "storage warehouse" where they are packaged into the egg.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Vitellogenesis is the process of yolk accumulation in the developing oocyte, which is crucial for the survival of the future embryo in oviparous species.

Step 2: Detailed Explanation:
Although yolk is eventually stored inside the eggs within the ovary (A), its precursor molecule, vitellogenin, is not synthesized there.
Under stimulation by estrogen (specifically \(17\beta\)-estradiol) produced by the ovarian follicle cells, the hepatocytes in the liver (C) synthesize vitellogenin.
The liver then releases vitellogenin into the bloodstream, where it is transported to the ovary and taken up by developing oocytes via receptor-mediated endocytosis to form yolk proteins.

Step 3: Final Answer:
The precursor yolk proteins are synthesized in the liver.