slide share Arosome reaction

1. Topic
Prepared by
Rajamoni saikia
M.Sc 1st semester
zoology

2.  It is only within the past 135 year that the sperms roll in fertilization has
been known .
 Anton van leeuwenhoek , the dutch microscopist who co-discovered sperm
in the 1670 s,
 Each sperm cell consist of a haploid nucleolus .
 In front of this compressed haploid nucleus lies the acrosomal vesicle , or
acrosome .
 The acrosome is derive from the cells Golgi apparatus and contain enzymes
that digest proteins and complex sugars .
 Acrosome +nucleus = sperm head .

3.  A second interaction between sperm and egg jelly result in the acrosome reaction .
 In a acrosome reaction in initiated by contact of the sperm with the egg jelly.
 Exocytosis occur in acrosomal vesicle .
 Proteolytic enzyme and proteasomes that digest a path through the jelly coat to
the egg surface .
 Sulphate containing polysaccharide bind to the specific receptor located on the
sperm cell membrane directly above the acrosomal vesicle .
 Thus acrosome reaction constitute a barrier to interspecific fertilisation .

4. Figure 47.3-1
Basal body
(centriole)
Sperm
head
Acrosome
Jelly coat
Sperm-binding
receptors
Vitelline layer
Egg plasma membrane

5. Figure 47.3-2
Basal body
(centriole)
Sperm
head
Acrosome
Jelly coat
Sperm-binding
receptors
Hydrolytic enzymes
Vitelline layer
Egg plasma membrane

6. Figure 47.3-3
Basal body
(centriole)
Sperm
nucleus
Sperm
head
Acrosome
Jelly coat
Sperm-binding
receptors
Hydrolytic enzymes
Vitelline layer
Egg plasma membrane
Actin
filament
Acrosomal
process

7. Figure 47.3-4
Basal body
(centriole)
Sperm
plasma
membrane
Sperm
nucleus
Sperm
head
Acrosome
Jelly coat
Sperm-binding
receptors
Fused
plasma
membranes
Hydrolytic enzymes
Vitelline layer
Egg plasma membrane
Actin
filament
Acrosomal
process

8. Figure 47.3-5
Basal body
(centriole)
Sperm
plasma
membrane
Sperm
nucleus
Sperm
head
Acrosome
Jelly coat
Sperm-binding
receptors
Fertilization
envelope
Cortical
granule
Fused
plasma
membranes
Hydrolytic enzymes
Vitelline layer
Egg plasma membrane
Perivitelline
space
EGG CYTOPLASM
Actin
filament
Acrosomal
process

9. Acrosome reaction
 Acrosome reaction is initiated by repeating polymer of fucose sulphate .
 When this sulphate binds to its receptor on the sperm the receptor activates
three sperm proteins .
1) A calcium transport channel that allows ca2+ to enter the sperm heat .
2) A sodium Na/H exchanger that pumps sodium ion into the sperm as it pumps
hydrogen ion out .
3) A phpospholipase enzyme that makes another second messenger the phospholipid
inositol trisphosphate (ip3) .
 Ip3 able to release calcium from inside the sperm .
 The elevated calcium level in a relatively basic cytoplasm triggers the fusion of
acrosomal membrane with the adjacent sperm cell membrane .
 Releasing enzyme that can lyse a path through the egg jelly to the vitelline
envelop.

10. It extend of the acrosomal process .
This protrusion arises through the polymerization of globular actin
molecules into actin filament.
The influx of calcium is thought to inactivate the protein RhoB in the
acrosomal region and mid piece of sea uracin sperm.
This GTP binding protein helps to active in polymrising actin to make the
acrosomal processes.

11. The acrosome reaction allow the sperm by exocytosis release of acrosomal
enzyme to penetrate the zona pellucida of the egg.
The species specific zona pellucida protein that serve as a sperm receptor
also stimulates a seri9es of event that lead to fusion between the plasma
membrane and outré acrosomal membrane.