Chapter 14

Chapter 14 - Chapter 14 Signal Transduction mechanisms Up...

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Chapter 14 Signal Transduction mechanisms Up until now we learned how a message travels from presynaptic cell to postsynaptic cell but, we don’t know what happens to that message when it reaches postsynaptic cell, how it is used or how does postsynaptic cell know what the message says or what to do? Fig 14-1 There are two kinds of cell to cell signaling Endocrine Hormones signaling molecule travels from one cell to another via bloodstream. Local Mediators just go from one cell directly onto another; therefore two cells have to be very close to each other. 1. Ligand (primary messenger) binds to specific site on the receptor, receptor is very specific to specific ligand, and not every ligand can bind to every receptor. 2. Receptors are always integral proteins (transmembrane) one part inside the cell and binding site (where ligand binds) outside of the cell. 3. Another thing involved in signal transduction is a second messenger, who gets the signal from the receptor and finally acts on it and cause some sort of response. The shape of the receptor changes as the ligand binds to it. The way the ligand binds to the receptors is called its affinity. o Also when ligand binds to receptors, causes receptors to move in the membrane and cluster together. Receptors can act in different ways One receptor can activate multiple pathways Different receptors can activate same pathway Different receptors can activate different pathways, and one pathway affects other. Signals can cause Survival of cell Grow and divide Differentiation Death 1. Two main kinds of receptors—for water soluble, hormones, growth factors, NT G-Protein linked receptor
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Protein Kinase receptor 2. Signal Casacade 3. 2 nd messenger—cAMP and Ca++ G-Protein linked Receptors o They interact with G proteins inside the cell o Have lots of alpha helices o Binds to messenger When it binds to messenger or ligand it changes its shape Protein kinase A are activated G protein is activated GDP turn into GTP (like on/off switch) Mechanism of G-protein linked receptor FIG 14-5 pg 397 1. When ligand binds to the G protein linked receptor it activates the regions of that G linked receptor that are kinases (protein kinase A). 2. This will cause GTP to bind to G protein and GDP will be lost a. GTP will bind to the alpha subunit 3. Alpha subunit will separate from beta and gamma subunits 4. Alpha subunit will go and activate protein 5. After activating a protein it will disassociate from that protein a. Lose GTP and comes back to GDP and again go back and bind to beta and gamma subunits. Acetyl choline receptors are usually ionotic receptor or direct receptor but, in heart they
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Chapter 14 - Chapter 14 Signal Transduction mechanisms Up...

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