acrosome reaction

Information about acrosome reaction

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Acrosome reaction on a Sea Urchin cell
The acrosome reaction is the reaction which occurs in the acrosome of the sperm as it approaches the zona pellucida.

As the sperm approaches the egg, the membrane surrounding the acrosome fuses with the plasma membrane of the sperm, exposing the contents of the acrosome and rendering the sperm capable of fusing with the egg.

Variations among species

There are considerable species variations in the morphology and consequences of the acrosome reaction. In several species the trigger for the acrosome reaction has been identified in a layer that surrounds the egg.

Lower animal species

In some lower animal species a protuberance (the acrosomal process) forms at the apex of the sperm head, supported by a core of actin microfilaments. The membrane at the tip of the acrosomal process fuses with the egg plasma membrane.

In some lower species, including starfish and sea urchins, a major portion of the exposed acrosomal contents is a protein that temporarily holds the sperm on the egg surface.

Mammals

In mammals the acrosome reaction releases hyaluronidase and acrosin; their role in fertilization is not yet clear.

It also alters a patch of pre-existing sperm plasma membrane so that it can fuse with the egg plasma membrane.

See also

External links

In spermatozoa of many animals, the Acrosome is an organelle that develops over the anterior half of the spermatozoon's head. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is completed during testicular maturation.
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sperm is derived from the word spermos (meaning "seed") and refers to the male reproductive cells. Sperm cells are the smaller gametes involved in fertilization.
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The zona pellucida (or zona striata in older texts) is a glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but not extraneous to it.
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Echinoidea
Leske, 1778

Subclasses
  • Subclass Perischoechinoidea
  • Order Cidaroida (pencil urchins)
  • Subclass Euechinoidea

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The hyaluronidases (EC 3.2.1.35 ) are a family of enzymes that degrade hyaluronic acid.

By catalyzing the hydrolysis of hyaluronic acid, a major constituent of the interstitial barrier, hyaluronidase lowers the viscosity of hyaluronic acid, thereby increasing tissue
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Acrosin (EC 3.4.21.10 ) is a digestive enzyme that acts as a protease.

Acrosin is released from the acrosome of spermatozoa as a consequence of the acrosome reaction.
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ZP3 is the receptor in the zona pellucida which binds with the acrosome of the sperm in the acrosome reaction.

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  • MeSH ZP3+protein,+human

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Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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