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22 Cards in this Set
- Front
- Back
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Chemical messengers |
communication is indirect- no direct contact |
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Receptors |
-most chemical messengers are water-soluble and bind to receptors located at the plasma membrane -Some messengers, like steroids, are lipid soluble and bind to an intracellular receptor |
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Receptor Specificity |
-not all cells express the same receptors -this selective expression leads to the specificity in the systems -the response of individual cells with the same receptor also vary based on cell type, intracellular signaling cascade coupling, and there simultaneous signals being received |
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Receptor Affinity |
degree to which a particular messenger binds to its receptor |
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Receptors: Competition Agonist |
-chemical which binds to receptor -action mimics normal response |
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Receptors: Competition Antagonist |
-Chemical which binds to receptor -binding does not result in response -competes with normal ligand -response is opposite of the agonist |
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Receptors: Regulation |
-Down regulation: decrease in target cell receptors -Up regulation: increase in target cell receptors |
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Signal Transduction |
-Response can be: -Permeability, transports properties, or electrical state of membrane -metabolism -secretory activity -rate of proliferation and differentiation -Contractile or other activities All de to alterations of particular cell proteins |
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Signal Transduction: Lipid Soluble Ligands |
-Requires carrier protein for transport in blood -easily crosses membrane -Receptor location within cell (intracellular location) -General action of target -A slower, but more sustained response |
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Signal Transduction: Water Soluble Ligands |
-Does not easily cross cell membrane, which may require pumps or channels -receptors on cell membrane -General action of target response enzyme activation membrane permeability changes -Tend to be more rapid responses |
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Cont. |
-Includes most peptide and protein hormones, neurotransmitters, and paracrine-autocrine compounds -have a broad range of receptors: ion channels, G-protein coupled receptors with intrinsic kinase activity, etc -receptors activate intracellular signaling cascades that affect cell function |
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Pathways Initiated by Water Soluble Messengers Essential terms: |
-First messenger: extracellular messenger that bind to specific membrane receptors -Second messenger: generated in the cytoplasm as a result of the first messenger binding -Protein Kinase: enzyme that phosphorylates a protein, thus changing its activity |
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Ligand-Gated Ion Channels |
-receptor and channel-same protein -action is direct -Change in transport of ions through channel often results in a change in membrane potential |
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Enzyme Linked Receptors |
-Receptor and enzyme- same protein -ligand binding activates enzyme -action is direct -activated enzyme caused target response -Insuline works this way |
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Type II Diabetes |
Cells no longer respond to the insulin that is produced |
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G Protein Coupled Receptors |
G Protein: have 3 subunits (alpha,beta,gamma) -Amplifier enzyme then activates 2nd messenger production -Types of 2nd messengers: Cyclic AMP-most common -G Proteins can either be stimulatory or inhibitory -G protein couple receptors are the most numerous type of receptor family and have a large variety of signaling pathways associated with them -while there are lots of subfamilies of plasma memoranda G proteins- focus on one: Adenyly Cyclase |
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Cyclic AMP as a 2nd messenger: Ex. Epinephrine |
-In fat cells, epinephrine stimulates breakdown of triglyceride, a process that is mediated by one phosphorylated enzyme -In liver- epinephrine stimulates glycogenesis and gluconeogenesis, processes that are mediated by phosphorylated enzymes that differ from those fat cells |
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Signal Amplification |
-small amounts of ligand can cause a huge response in target -each step recruits more participants -characteristic of 2nd messengers |
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Control of ion channels by G Proteins |
-An ion channel can be the effector protein for a G Protein -Direct regulation: G protein interacts with the channel without second messengers -Indirect regulation: Second messengers are used (Ex. Epinephrine) |
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Other messengers: Eicosanoids |
-Aspirin and other NSAIDs inhibit the Cyclooxyrgenase pathway -People do not take these before surgery because they prevent blood clotting |
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Cessation of Activity in Signal Transduction Pathway |
-STPs are eventually shut off -Key event is usually cessation of receptor activation -Decrease in concentration of the 1st messenger -Messenger may be broken by enzymes, bind to adjacent cells, or diffuse away -Alternatively, receptor may: Become chemically altered which lowers affinity for 1st messenger. Become phosphorylated to prevent further g protein binding to the receptor. Be removed when the combination of the 1st messenger and receptor is take into the cell by endocytosis. |
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Interactions of STPs |
Pathways do not exist in isolation but may be active simultaneously in a singe cell undergoing complex interactions. |
