Summary
Egg coat proteins bind sperm and calcium waves activate development after fusion.
In depth
At fusion, a sperm factor (PLCζ) triggers calcium oscillations; cortical granules release enzymes that harden the zona and cleave ZP2. The egg resumes meiosis. Defects cause infertility.
Egg activation resumes the cell cycle and triggers metabolic changes. Failure leads to fertilisation failure.
Remember: calcium is the universal trigger.
The zona pellucida is a glycoprotein coat around mammalian oocytes made of ZP1 to ZP4 proteins. It mediates species-specific binding of sperm, triggers the acrosome reaction, and after fertilisation hardens to block polyspermy and protects the early embryo until hatching.
When the sperm fuses with the egg membrane, it delivers phospholipase C zeta, which triggers IP3 release and waves of calcium oscillations in the egg. This activates cortical granule exocytosis, completion of meiosis II, resumption of the cell cycle, and metabolic activation. Artificial activation with calcium ionophores can help some failed fertilisations.
Example: antibodies to ZP proteins are explored as contraceptives.
Key idea: calcium is the universal start signal for development.
Frequently asked questions
What is Zona Pellucida and Egg Activation?
Egg coat proteins bind sperm and calcium waves activate development after fusion.
Which area of biology covers Zona Pellucida and Egg Activation, and how advanced is it?
Zona Pellucida and Egg Activation 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, Sperm Capacitation and Acrosome Reaction, Implantation.
Can you give an example of Zona Pellucida and Egg Activation?
Artificial egg activation uses calcium ionophores in some IVF cases.
What should I learn before Zona Pellucida and Egg Activation?
Work through the Beginner topics in Reproduction & Endocrinology first, such as Reproduction, Asexual Reproduction, Sexual Reproduction, then return to Zona Pellucida and Egg Activation. Advanced topics assume the Intermediate vocabulary.
What topics are related to Zona Pellucida and Egg Activation?
The closest topics to Zona Pellucida and Egg Activation are Fertilisation Process, Sperm Capacitation and Acrosome Reaction, Implantation, Ovulation. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Zona Pellucida and Egg Activation?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Zona Pellucida and Egg Activation. To practise the whole of Reproduction & Endocrinology, use the Reproduction & Endocrinology quiz.
How is Zona Pellucida and Egg Activation different from Fertilisation Process?
Zona Pellucida and Egg Activation: Egg coat proteins bind sperm and calcium waves activate development after fusion. 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 Zona Pellucida and Egg Activation 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.