#calcium signaling

Sea urchin -lll

The primary molecule triggering calcium release during sea urchin fertilization is:

At sea urchin fertilization, sperm-egg fusion activates Src family tyrosine kinases that phosphorylate and activate phospholipase C-gamma. PLC-gamma hydrolyzes phosphatidylinositol bisphosphate PIP2 in plasma membrane into diacylglycerol DAG and inositol trisphosphate IP3. IP3 diffuses to endoplasmic reticulum binding IP3 receptors, opening calcium channels and initiating calcium wave from internal stores propagating across egg. This IP3-triggered calcium release drives cortical granule exocytosis, elevation of fertilization envelope, and resumption of meiosis. Zona glycoproteins and protamines do not directly trigger intracellular calcium release.

Ref: NCBI Bookshelf, Molecular Biology of the Cell, Chapter: IP3 triggers calcium release during sea urchin fertilization.

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Fertilization in mammals-iv

Egg activation triggered by:

Egg activation is series of events initiating embryonic development after sperm entry, including cortical granule exocytosis, resumption of meiosis, pronuclear formation and maternal mRNA recruitment. Primary trigger is repetitive intracellular calcium oscillations generated by sperm-introduced phospholipase C zeta hydrolyzing PIP2 to IP3, releasing calcium from endoplasmic reticulum. Calcium wave activates CaMKII, degrades cyclin B, reduces MAPK activity and triggers zinc spark. Sodium, potassium or magnesium influx cannot initiate this cascade; calcium-calmodulin signaling is universal activator conserved from sea urchin to mammals, linking fertilization to developmental program onset.

Ref: Molecular Biology of the Cell, Chapter 20: Egg activation - PLC zeta induced calcium oscillations and cortical reaction.

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A Cell Signaling

Second messenger that opens Ca²⁺ channels on ER membrane is:

IP₃, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling GPCR Pathways - I

Low Ca2+ levels in rods activate

guanylyl cyclase, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling GPCR Pathways - I

Ryanodine receptors amplify Ca2+ signaling via

positive feedback, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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