Practice question

Hyperactivation, characterized by high-amplitude asymmetric flagellar beating generating enhanced thrust for cumulus and zona penetration, depends absolutely on calcium entry through CatSper, sperm-specific voltage and pH sensitive calcium channel complex localized to principal piece flagellum. Subunits CatSper1-4 plus auxiliary proteins form heteromeric pore gated by intracellular alkalinization and progesterone removing endocannabinoid inhibition. Calcium influx activates calmodulin, altering dynein sliding pattern. CatSper knockout males are infertile despite normal counts, sperm unable to hyperactivate or ascend oviduct, confirming channel indispensability for fertilization competence, species propagation, reproductive fitness and successful penetration.