what is the function of acvosome in the sperm cell
Answers
The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa (sperm cells) of many animals including humans. It is a cap-like structure derived from the Golgi apparatus. In Eutherian mammals the acrosome contains digestive enzymes (including hyaluronidase and acrosin).
Answer:
Acrosome
Definition, Function, Reaction and Exocytosis
Definition: What is an Acrosome
The acrosome is one of the main components of a sperm cell overlying the nucleus. It is located on the anterior part of the sperm head where it serves a number of important roles related to fertilization.
* Introduced in 1898 by Lenhossek, the term translates to apical body or tip body.
The acrosome develops during spermiogenesis and is the product of the Golgi complex. Here, the biogenesis starts when proacrosomic vesicles generate from the Golgi complex belonging to early spermatids. The vesicles then combine forming a single, dense, acrosomic vesicle that ultimately extends to cover about two-thirds of the nuclear surface.
Explanation:
Functions of the Acrosome
Transformation of the Sperm Head
The acrosome is involved in the transformation (shaping) of the sperm head through the Acrosome–Acroplaxome-manchette complex. Here, the two important structures involved are acroplaxone and manchette.
The acroplaxone (consisting of actin and keratin) overlays the acrosome and its complex with manchette contribute to the following:
Development of acrosomal sac
Anchoring acrosome to the nuclear envelope
Transformation of the sperm cell
* By shaping the acrosome, the complex allows the acrosome to shape the sperm head during spermiogenesis.
Gamete Recognition
In such animal as frogs and sea urchin, proteins referred to as primary ligands have been shown to play an important role in gamete recognition. Although these ligands are usually located on the plasma membrane surface, some have been identified on the acrosome thus involving the organelle in gamete recognition.
Once the primary ligands identify specific proteins in the jerry surrounding the egg, they initiate binding.
Acrosome Reaction and Exocytosis
Acrosome Reaction
When the spermatozoa (or primary ligands of the sperm) come into contact with the jerry layer that surrounds the female gamete (the egg) acrosome reaction/exocytosis is initiated.
Before the sperm can undergo acrosome exocytosis, it goes through a process known as capacitation.
Here, the sperm undergoes a number of physiological changes that include:
The plasma membrane of the sperm loses cholesterol
Soluble acrosome reaction is activated
The second messenger cyclic AMP is generated
Protein kinases activation
Once the sperm cells have gone through these changes in the female reproductive tract, they are ready for exocytosis.
When the sperm cell comes into contact with the external coat of the female gamete (the zona pellucida), some of the primary ligands (lectins) bind to the receptors molecules of ZP3 (O-linked oligosaccharides and glycans) thus binding the two gametes.
This process has been linked with ensuring that the sperm binds to the egg in a species-selective manner that allows for acrosome exocytosis (also referred to as acrosome reaction). Acrosome is calcium dependent and involves acrosome exocytosis.
Here, binding of the sperm to the egg is accompanied by the formation of numerous pores between the acrosome membrane and the plasma membrane of the sperm cell at the sperm head.
This reaction not only results in the fusion of the two membranes (the plasma membrane of the sperm cell and the acrosome membrane), but also allows contents of the acrosome to be released. Acrosome reaction has two main outcomes