The
acrosome is an
organelleIn cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid membrane....
that develops over the anterior half of the head in the
spermatozoaA sperm, from the ancient Greek word σπέρμα and and more commonly known as a sperm cell, is the haploid cell that is the male gamete. It joins an ovum to form a zygote. A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.Sperm cells contribute...
(sperm cell) of many animals. It is a cap-like structure derived from the
Golgi apparatusThe Golgi apparatus is an organelle found in most eukaryotic cells...
. Acrosome formation is completed during testicular maturation. In
EutheriaEutheria are a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from non-eutherians by various features of the feet, ankles, jaws and teeth...
n mammals the acrosome contains digestive
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
s (including
hyaluronidaseThe hyaluronidases are a family of enzymes that degrade hyaluronic acid.In humans, there are six associated genes, including HYAL1, HYAL2, HYAL3, and PH-20/SPAM1.-Use as a drug:...
and
acrosinAcrosin is a digestive enzyme that acts as a protease.Acrosin is released from the acrosome of spermatozoa as a consequence of the acrosome reaction....
). These enzymes break down the outer membrane of the
ovumAn ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
called the
zona pellucidaThe zona pellucida 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...
, allowing the haploid
nucleiIn cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as...
in the sperm to join with the haploid nucleus found in the ova.
This shedding of the acrosome or
acrosome reactionDuring fertilization, sperm must first fuse and then penetrate the female egg in order to fertilize it. Fusing to the egg usually causes little problem whereas penetrating through the egg's hard shell can present more of a problem to the sperm...
can be stimulated in vitro by substances a sperm cell may encounter naturally such as
progesteroneProgesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...
or
follicular fluidFollicular fluid is a liquid which fills the follicular antrum and surrounds the ovum in an ovarian follicle. This fluid is rich in hyaluronic acid.-External links:* *...
, as well as the more commonly used calcium
ionophoreAn ionophore is a lipid-soluble molecule usually synthesized by microorganisms to transport ions across the lipid bilayer of the cell membrane...
A23187.
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The
acrosome is an
organelleIn cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid membrane....
that develops over the anterior half of the head in the
spermatozoaA sperm, from the ancient Greek word σπέρμα and and more commonly known as a sperm cell, is the haploid cell that is the male gamete. It joins an ovum to form a zygote. A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.Sperm cells contribute...
(sperm cell) of many animals. It is a cap-like structure derived from the
Golgi apparatusThe Golgi apparatus is an organelle found in most eukaryotic cells...
. Acrosome formation is completed during testicular maturation. In
EutheriaEutheria are a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from non-eutherians by various features of the feet, ankles, jaws and teeth...
n mammals the acrosome contains digestive
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
s (including
hyaluronidaseThe hyaluronidases are a family of enzymes that degrade hyaluronic acid.In humans, there are six associated genes, including HYAL1, HYAL2, HYAL3, and PH-20/SPAM1.-Use as a drug:...
and
acrosinAcrosin is a digestive enzyme that acts as a protease.Acrosin is released from the acrosome of spermatozoa as a consequence of the acrosome reaction....
). These enzymes break down the outer membrane of the
ovumAn ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
called the
zona pellucidaThe zona pellucida 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...
, allowing the haploid
nucleiIn cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as...
in the sperm to join with the haploid nucleus found in the ova.
This shedding of the acrosome or
acrosome reactionDuring fertilization, sperm must first fuse and then penetrate the female egg in order to fertilize it. Fusing to the egg usually causes little problem whereas penetrating through the egg's hard shell can present more of a problem to the sperm...
can be stimulated in vitro by substances a sperm cell may encounter naturally such as
progesteroneProgesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...
or
follicular fluidFollicular fluid is a liquid which fills the follicular antrum and surrounds the ovum in an ovarian follicle. This fluid is rich in hyaluronic acid.-External links:* *...
, as well as the more commonly used calcium
ionophoreAn ionophore is a lipid-soluble molecule usually synthesized by microorganisms to transport ions across the lipid bilayer of the cell membrane...
A23187. This can be done to serve as a positive control when assessing the acrosome reaction of a sperm sample by
flow cytometryFlow cytometry is a technique for counting and examining microscopic particles, such as cells and chromosomes, by suspending them in a stream of fluid and passing them by an electronic detection apparatus. It allows simultaneous multiparametric analysis of the physical and/or chemical...
or
fluorescence microscopyA fluorescence microscope is a light microscope used to study properties of organic or inorganic substances using the phenomena of fluorescence and phosphorescence instead of, or in addition to, reflection and absorption.- Technique :In most cases, a component of interest in the specimen is...
. This is usually done after staining with a fluoresceinated
lectinLectins are sugar-binding proteins which are highly specific for their sugar moieties. They typically play a role in biological recognition phenomena involving cells and proteins...
such as FITC-PNA, FITC-PSA, FITC-ConA, or fluoresceinated antibody such as FITC-CD46.