01:119:116 Lecture Notes - Lecture 16: Zona Pellucida, Acrosome Reaction, Polyspermy
15 Mar 2016
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Document Summary
All changes that occur during entire life cycle of an individual: embryonic, following birth/hatching. Model organisms: sea urchin, frog (fig 47. 2, chick, nematode. Zygote fertilized egg, single cell: consequences. Development: egg surrounded by plasma membrane and one or more coverings. Aid in fertilization by sperm of same species. Sperm dissolves around egg to reach plasma membrane. Molecules on sperm surface bind to receptors on egg surface. Surface of egg changes to prevent polyspermy: sea urchin. Protrudes from sperm head and penetrates coat. Bind to receptors on egg plasma membrane. Unfertilized egg: polarized, cytoplasm negatively charged relative to outside. Within seconds after sperm fuses: ion channels in egg plasma membrane open. Egg depolarize: occurs 1-3 sec after sperm binds to egg. Slow block to polyspermy via certical reaction. Binding of sperm to egg: triggers signal transduction pathway, triggers release of ca2+ from er into cytoplasm. Cortical granules: vesicles which lie in cortex.
