Practice question

Resact is fourteen amino acid peptide purified from egg jelly of Arbacia punctulata that guides sperm chemotaxis toward egg. It binds high-affinity receptors on sperm flagellum coupled to guanylate cyclase, increasing cGMP and calcium oscillations altering flagellar waveform and steering toward gradient source. Chemotactic response is highly selective; Arbacia sperm respond strongly to Resact at picomolar concentrations, while Strongylocentrotus sperm show minimal response, preferring Speract. This species specificity enhances conspecific fertilization assurance when multiple species spawn simultaneously, contributing to reproductive isolation and preventing hybridization in broadcast spawning marine environment, improving fertilization success significantly.