- A It is sometimes thought to be generally the ordinary outer plasma membrane that surrounds the egg cell itself, nothing more biochemically specialized during normal conditions as generally observed
- B A glycoprotein matrix around the oocyte; ZP3 acts as sperm receptor triggering acrosome reaction; ZP2 binds acrosin post-acrosome reaction; after fertilization it hardens to prevent polyspermy
- C It is sometimes thought to produce progesterone hormone directly itself, helping to maintain the lining of the uterine endometrium each cycle in typical laboratory settings under usual circumstances
- D It is sometimes thought to be largely shed away from the surface of the oocyte well before ovulation itself actually takes place according to most researchers in the majority of cases studied
Correct answer: B. A glycoprotein matrix around the oocyte; ZP3 acts as sperm receptor triggering acrosome reaction; ZP2 binds acrosin post-acrosome reaction; after fertilization it hardens to prevent polyspermy
Explanation: Zona pellucida (ZP): glycoprotein matrix secreted by oocyte. ZP3 binds species-specific sperm receptors and triggers the acrosome reaction. ZP2 is the secondary binding protein after acrosome reaction. After fertilization, cortical reaction releases enzymes that modify ZP2/ZP3 (zona hardening), preventing additional sperm from penetrating.
Concept context
Male and female reproductive systems, gametogenesis, fertilization, implantation, pregnancy, and reproductive health.