Summary
Sperm undergo biochemical changes that let them penetrate the egg's protective layers.
In depth
Capacitation in the female tract removes cholesterol and changes membrane and calcium signalling; hyperactivated motility. Zona proteins (ZP3) trigger acrosome exocytosis, releasing hyaluronidase and acrosin; IZUMO1 on sperm binds JUNO on the egg for fusion.
Capacitation takes hours in the female tract. Calcium influx hyperactivates the flagellum. Acrosome enzymes digest a path through the zona.
Example: acrosome-intact sperm bind the zona first.
Freshly ejaculated sperm cannot fertilise an egg. Capacitation, taking hours in the female tract, involves removal of cholesterol from the sperm membrane, increased membrane fluidity, rises in intracellular calcium and cAMP, protein tyrosine phosphorylation and hyperactivated, whip-like flagellar motion.
Capacitated sperm bind to the zona pellucida (via ZP3 receptors), triggering the acrosome reaction, where the acrosomal membrane fuses with the plasma membrane and releases hyaluronidase and acrosin to digest a path through the zona. The newly exposed membrane protein IZUMO1 binds the egg receptor JUNO to fuse the gametes.
Example: in IVF, sperm are washed to allow capacitation.
Remember: both steps are needed for fertilisation.
Frequently asked questions
What is Sperm Capacitation and Acrosome Reaction?
Sperm undergo biochemical changes that let them penetrate the egg's protective layers.
Which area of biology covers Sperm Capacitation and Acrosome Reaction, and how advanced is it?
Sperm Capacitation and Acrosome Reaction is one of the 54 topics in Reproduction & Endocrinology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Fertilisation Process, Zona Pellucida and Egg Activation, Steroid and Peptide Hormone Mechanisms.
Can you give an example of Sperm Capacitation and Acrosome Reaction?
ICSI bypasses these steps.
What should I learn before Sperm Capacitation and Acrosome Reaction?
Work through the Beginner topics in Reproduction & Endocrinology first, such as Reproduction, Asexual Reproduction, Sexual Reproduction, then return to Sperm Capacitation and Acrosome Reaction. Advanced topics assume the Intermediate vocabulary.
What topics are related to Sperm Capacitation and Acrosome Reaction?
The closest topics to Sperm Capacitation and Acrosome Reaction are Fertilisation Process, Zona Pellucida and Egg Activation, Steroid and Peptide Hormone Mechanisms, Gametes. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Sperm Capacitation and Acrosome Reaction?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Sperm Capacitation and Acrosome Reaction. To practise the whole of Reproduction & Endocrinology, use the Reproduction & Endocrinology quiz.
How is Sperm Capacitation and Acrosome Reaction different from Fertilisation Process?
Sperm Capacitation and Acrosome Reaction: Sperm undergo biochemical changes that let them penetrate the egg's protective layers. Fertilisation Process: The sperm penetrates the egg, triggering the cortical reaction that blocks other sperm. Read both side by side and note what each one explains.
How should I study Sperm Capacitation and Acrosome Reaction step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Fertilisation Process and explain the difference aloud. Finally, take the Reproduction & Endocrinology quiz and come back to this page for any question you miss.