Developmental Exam 1
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What is the capping phenomenon?
When the Membrane Binding Proteins that surround the sperm head concentrate around the tip of the sperm head, which becomes the contact point for the egg & sperm. It occurs when there is a cholesterol eflux from the sperm, which creates big pores within the plasma membrane. cholesterol has OH groups that fit in the plasma layer perfectly.
What are the 3 steps of Signal Transduction?
- 1. Egg & Sperm Recognition
- 2. Capacitation
- 3. Chemotaxis
What is Egg & Sperm Recognition?
It is necessary to make the sperm more motile. Sperm must be activated and it must occur within the female reproductive tract.
How is the sperm activated?
- Sperm must enter the female reproductive tract, where it travels through a LOW CO2 and High pH BASIC, which causes Na+ influx and H+ eflux.
What is the entire signal transduction process?
Immobile sperm enters the female reproductive tract which is BASIC and LOW CO2 conentration this cause a Na+ influx & H+ eflux spearact from the egg binds to its receptor in the sperm head which activates second messenger GTP to activate guanylate cyclase resulting in cGMP. This cause a K+ eflux, resulting in the hyperpolarization of the spermhead (because it is becoming slightly more negative) CREB binds to cAMP activating it as the spermhead tries to neutralize its pH with the Na+ & H+ influx & eflux. With the activation of cAMP transcription factors get going & Ca2+ influx is created, Na/K pumps are opened kicking out 2K's for every 3Na's. the ova then makes and releases ZP1,ZP2, & ZP3 proteins, when the ZP3 protein & receptor bind together carbohydrates come in and contaminate the membrane, preventing polyspermy, and Ca+/T-channels are activated which create a Ca+ influx (in the egg?)
What are the issues with generic binding proteins?
- they do not bind tightly, which means that they can fall off.
Very Species Specific. In sea urchins it is a protein on the sperm's acrosome surface that mediates fusion to the sea urchin egg.
May activate Acrosome Rxn, and used for sperm-egg recognition
protein in egg membrane; 10 amino acids long
What is Resact?
protein on the egg surface; 14 amino acids long
Where are the spearact receptors located?
in the sperm
What are two proteins found in the sea urchin egg membrane?
What are 3 proteins in Egg membrane?
Where are the ZP1,ZP2, & ZP3 receptors located?
in the sperm & acrosome
What are some characteristics of Signal Transduction?
- Occurs on both egg & sperm sides
- Receptor Ligand Driven
- Occurs very quickly
- Huge Ion Influx
- Increase in Membrane fluidity (b/c of Ca Eflux)
What is a TATA Box?
Generic Binding Protein/Controller/Transcription Factor located on the 3' end
What are enhancers?
Specific Binding Proteins/Transcription Factors that bind tightly
What is a Transcription Factor?
a binding protein that controls the flow of gene inflo
Which protein is needed for sperm capacitation? Why?
ZP3 becasue the sperm is attracted to the ZP3 protein and actually gravitates toward it.
Which of the Z proteins are longer?
ZP2 & ZP3
Which Z's cross-link "hold the other" together?
ZP1 & ZP2
- when ZP3 & its receptor bind they cause carbohydrates to come in & contaminate the egg membrane
Another word for Ca+ Channel
What are two necessary components for the activation of the Acrosome Rxn?
- - Ca2+
- - fusion of sperm & egg membranes
Name 3 dyes that glow when bound to Ca2+
- -Indole 3
- -Furan 2
Describe Mammalian Capacitation
RECEPTOR-LIGAND INTERACTION WITH MUSCARINIC RECEPTORS OF THE ZP3
ACTIVATION OF G-PROTEIN CREATES A TRIMER THAT KICKS OUT GDP & TAKES IN GTP. THE ALPHA SUBUNT ALONG WITH GTP DISSOCIATES ALONG THE CELL MEMBRANE WHICH THEN TARGETS adenyl cyclase & phosphotidal inosital (PI-PLC)
What does the ATP Activation of Adenyl Cyclase lead to?
Adenyl Cyclase Activation by ATP produces cAMP +PO4
What is the off-switch in Mammalian Capacitation?
Why is it okay that zp3 is not species specific?
because female mammals are selective maters
Why is it necessary that speract & Resact are species Specic?
because of external fertalization. Mates are not choosy.
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