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13 Cards in this Set
- Front
- Back
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What is the maind difficulty in transducing a signal outside a cell?
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The cell membrane is pretty much impermiable to all but the simplest molecules.
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What are the two major classifications of signal transduction?
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Membrane receptors and intracellular receptors.
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What is a ligand, why is it important to signal transduction?
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A ligand is something that binds to a receptor. Based on the ability of a ligand to move across the cellular membrane, there are two classes of receptors. If the ligand can only bind on the outside of a cell, or on its surface, the receptor is called a membrane receptor. If the ligand can move into the cell and bind, the receptor is called a intracellular receptor.
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what are the five catagories given to signaling molecules based on their site of secretion and their site of action?
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Endocrine, acts throughout the body (insulin)
Paracrin, acts locally (vasodiolation) Autocrine, acts on itself (interleukin) Juxtacrine, signals are transmitted along the cell membrane and are capable of affecting the cells directly next to it. Synaptic, these very effecient signaling actions are confined within a vary small space like a neuron. |
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The three histamine receptors (H1, H2, and H3) all bind histamine, but what are the two differences in their response to histamine?
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H1 binds histidine to produce nasal and sinus secretions
H2 binds histidine to produce gastric secretions. H3 receptors are found in the brain and are important in sleep dissorders. |
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Ciproxifan is a potent and specific histamine H3 receptor antagonist. Whould it be expected to alleviate allergy symptoms or suppress gastric activity?
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No, it would only react with the H3 receptor, and not the H1 (nasal secretions) or the H2 (gastric secretions)
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Name 5 second messenger molecules?
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cAMP. IP3,DAG,Arachidonic acid,cGMP.
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Suppose a cell is expressing the adenosine receptor. How can the cell be made less responsive to adenosine in the circulation, even when adenosine is present at high enough concentration that under normal conditions it would cause a response?
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You can desensitize a reaction by either reducing receptor affinity or by introducing an inhibitor.
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Describe the role of the proto-onco gene ras in the intracellular signaling transduction.
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RAS is a signal transduction protien. Defects in it may lead to the overexpression of genes and thus tumors. It is common in most cancers, being found in 20-30% of all cancer.
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Describe the mechanism of cytokines as related to signal transduction.
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Cytokines bind to cell receptors and cause a cascade of events that may either raise or lower the level of other cytokines, change the level of surface receptors, or inhibit their own effect by feedback inhibition.
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What enzymatic activity is found on the receptor involved in cholera? What enzymatic activity is found on the protein subunits that associate with the receptor involved in cholera? In what way does cholera toxin affect this activity? What is the physiological consequence of this altered enzymatic activity?
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Cholera blocks GTPase activity of G proteins. The G protein is essentially "stuck on" and continuously produces cAMP. Excess secretion by the affected cell can cause diarrhea, dehydration or death.
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What molecule that is a precursor for a lipid involved in signal mediation of inflamation, blod clotting, control of vascular tone, pain, fever, is released from membranes by a phospholipase?
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Arachidonic acid.
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Paradoxically, what drug id useful in treating congestive heart failur?
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B blocker. Even though nomally b blockers would decrease the rate of contraction of the heart, they also raise the ejection fraction of the heart.
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