Practice question

Sea urchin egg jelly contains diffusible peptides that attract sperm via chemotaxis. Purified factors Resact from Arbacia punctulata and Speract from Strongylocentrotus purpuratus are small 10-14 amino acid sulfated peptides. They bind receptors on sperm flagellum activating membrane guanylate cyclase, increasing cGMP, calcium influx, and altering flagellar beating to orient toward gradient source. This chemotaxis enhances encounter rates in seawater where dilution is extreme. Bindin and Hyalin are structural adhesion proteins, acrosin is acrosomal protease, not chemoattractants, leaving Resact and Speract as established sperm attraction peptides guiding fertilization.