Practice question

Egg cytoplasmic calcium rise is triggered by diffusible second messenger inositol 1,4,5-trisphosphate IP3 acting on endoplasmic reticulum calcium stores. IP3 binds ligand-gated IP3 receptors, tetrameric channels releasing sequestered calcium producing self-propagating wave due to calcium-induced calcium release. Upstream sperm factor activates Src-family kinase that phosphorylates and recruits phospholipase C gamma to membrane where it cleaves PIP2 into DAG and IP3. Cyclic AMP predominates in sperm chemotaxis signaling, diacylglycerol activates protein kinase C regulating Na+/H+ exchange, ATP fuels processes but does not gate calcium release directly; IP3 is immediate chemical trigger.