User:R.axel630/Vitellin

Vitellin serves several functions, especially during fertilization and embryonic development.

This phosphoprotein acts as a membrane, 1-3.5μm, that encloses the egg that comprises at least five glycoproteins that resemble the zona pellucida evident in mammalian organisms. When the egg is fertilized, it buds off from the gamete surface, which results in the fertilization of the membrane in most invertebrates, amphibians, birds, and fishes. During fertilization, the acrosome of the sperm interacts with the vitelline envelope that has species-specific recognition and binding for the sperm. The vitelline membrane consists of two major layers found below the ovary and the outer layer found in the oviduct. This membrane supports the yolk and separates from the albumen, or egg white. The proteins that primarily compose the vitelline membrane are the lysozyme and ovomucin foundational for membrane growth during embryonic development. Aside from structural functions, it is also a barrier that permits the diffusion of water and nutrients, and in chickens especially, it is a barrier against microbial infection. Vitellin comprises a vast fraction of the proteins found in eggs, and due to this, they are easily characterized with biochemical methods in order to elucidate molecular, developments, and physiological regulation studies.