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The egg cell or ovum (pl.: ova) is the female reproductive cell, or gamete, [1] in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non- motile ).
The zona pellucida is an extracellular matrix that surrounds the plasma membrane of the egg cell. It helps protect the egg, and has an essential role in fertilization by sperm. It is surrounded by the corona radiata. The corona is composed of cells that care for the egg when it is emitted from the ovary. [1]
In the chicken egg, the yolk is separated from the albumen by the vitelline membrane which acts as a barrier to microbial infection. [7] Apart from the 13 proteins identified [4] to make up the membrane, the proteins that are key to providing antimicrobial properties to the membrane are the vitelline outer membrane proteins (VMO) 1 [8] and 2. [7]
Eggshell membrane is the clear film lining the chicken eggshell displayed. Eggshell membrane or shell membrane is the clear film lining eggshells, visible when one peels a boiled bird egg. Chicken eggshell membranes are used as a dietary supplement. Eggshell membrane is derived commercially from the eggshells of industrial processors.
Mesolecithal eggs have comparatively more yolk than the microlecithal eggs. The yolk is concentrated in one part of the egg (the vegetal pole), with the cell nucleus and most of the cytoplasm in the other (the animal pole). The cell cleavage is uneven, and mainly concentrated in the cytoplasma-rich animal pole. [3]
Although membrane proteins play an important role in all organisms, their purification has historically, and continues to be, a huge challenge for protein scientists. In 2008, 150 unique structures of membrane proteins were available, [14] and by 2019 only 50 human membrane proteins had had their structures elucidated. [13]
Egg activation is stimulated by mechanical deformation associated with traversing through the narrow channel in the oviduct and requires the presence of Ca2+. [3] During egg activation, the vitelline membrane proteins are crosslinked via disulfide remodeling; the structure rigidifies and becomes impermeable to water but remains gas permeable. [ 4 ]
The sperm may trigger egg activation via the interaction between a sperm protein and an egg surface receptor. Izumo is the sperm cell signal, that will trigger the egg receptor Juno . [ 2 ] This receptor is activated by the sperm binding and a possible signaling pathway could be the activation of a tyrosine kinase which then activates ...