The sperm penetrates the zona pellucida of the egg.
How Sperm Penetrates an Egg
Sperm penetration is a multi-step process. The sperm does not immediately fuse with the egg. The process involves:
- Migration through follicle cells: The sperm first travels through the layer of follicle cells surrounding the egg.
- Binding to the zona pellucida: Next, the sperm binds to the zona pellucida, which is the egg coat. This is the area that the sperm penetrates.
- Fusion with the egg plasma membrane: Finally, the sperm binds to and fuses with the egg plasma membrane.
Breakdown of Egg Penetration
To further understand, here's a more detailed breakdown:
| Step | Description |
|---|---|
| 1. Follicle Cell Passage | Sperm moves through the layer of follicle cells surrounding the egg. |
| 2. Binding to Zona Pellucida | The sperm binds to and then penetrates the egg's outer coat called the zona pellucida. |
| 3. Plasma Membrane Fusion | The sperm then fuses with the egg's plasma membrane, allowing the sperm's genetic material to enter the egg. |
The zona pellucida is a critical component for sperm penetration. It plays a crucial role in ensuring species-specific fertilization and preventing polyspermy (fertilization by multiple sperm).
