DBLecture3posted

DBLecture3posted - Step one: Contact between the sperm and...

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Step one: Contact between the sperm and the eggshell
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Step two: Contact between the sperm and the egg’s plasma membrane
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Fertilization: a multistep process (ECM)
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Sperm-eggshell contact triggers the acrosome reaction Example 1-- the sea urchin enzymes Species specificity (equivalent to zona pellucida)
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attracts/activates sperm Figure 7.8
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Sperm-eggshell contact triggers the acrosome reaction Example 2: Mammals Sperm have ZP3 receptor
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Figure 7.8
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BLOCKING POLYSPERMY 1. Fast/transient: prevent sperm fusion 2. Slow/permanent: removal of other bound sperm
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Fast block 1-3 seconds lasts 1 min Slow block 20-60 seconds permanent
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How do we know this? We can measure these events directly! Figure 7.17 Membrane potential of sea urchin eggs before and After fertilization. resting -70 (sperm can fuse with egg) (sperm can’t fuse with egg) +20 mV
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Cortical granules: poised for release 15,000 cortical granules in a sea urchin egg contain enzymes that clip the egg’s bindin receptor and any attached sperm alter the vitelline envelope (zona pellucida in mammals) Blocking polyspermy: SLOW BLOCK Figure 7.6
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Sperm-eggshell contact triggers the acrosome reaction Example 2: Mammals Sperm have ZP3 receptor
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A wave of increased calcium can be visualized moving across the egg from the point of sperm entry Figure 7.20
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Fast block 1-3 seconds lasts 1 min Slow block 20-60 seconds permanent
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This note was uploaded on 05/26/2011 for the course BIO 205 taught by Professor Reed during the Spring '11 term at UNC.

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DBLecture3posted - Step one: Contact between the sperm and...

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