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24 Cards in this Set
- Front
- Back
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What are the 4 life or death consequences for cells controlled by signals?
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1) Survival
2) Growth and division 3) Differentation 4) Programmed death (apoptosis) |
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Where are most receptors located?
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at the cell surface
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Why are signals important?
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Signals tell cell whether they are in the right environment and whether it is appropriate to divide or differentiate in that environment. Normal cells removed from correct environment usually die.
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What are the 4 forms of intracellular signaling?
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1) Contact dependent
2) Paracrine (signals released into extracellular space and act locally on neighbor cells) 3) Synaptic 4) Endocrine |
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What are three types of cell-surface receptors?
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1) Ion channel-linked
2) G-protein linked 3) Enzyme linked (tyrosine kinases) |
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In what type of signaling pathways is phosphorylation required?
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Activation of both enzyme-linked and Gprotein-linked pathways
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What is the role of phosphatases?
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TOpposes phosphorylation in signalizing pathways by turning off signals as rapidly as they are turned on.
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How is adenlylyl cyclase activated?
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the alpha subunit of the trimeric G-protein detaches upon exchanging GTP for GDP and binds to an activating site on adenylyl cyclase
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What does activated adenlylyl cyclase produce, and what does this compound activate in turn?
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cAMP, then cAMP activates A-kinase, which elevates glucose levels by breaking down stored glycogen.
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Besides adenlylyl cyclase, what can G-protein receptors stimulate formation of?
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Phospholipase C-Beta, which then targets PIP2. PIP2 is then cleaved into IP3 and diacylglycerol as second messengers.
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What does IP3 do?
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Opens gated Ca++ release channels in the ER membrane, which binds to and activates calmodulin, which in turn activates breakdown of glycogen (Just like A-kinase!!!)
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Most growth factor receptors have what kind of activity in their cytoplasmic domains?
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tyrosine-specific protein kinase activity
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What is an important secondary signaling molecule in enzyme-linked signal transduction?
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Phopholipase C-gamma, which cleaves PIP2 into IP3 and diacylglycerol (like G-protein-linked receptors).
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What do Receptor Tyrosine Kinases indirectly activate through intermediate proteins?
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The monomeric protein ras.
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What role does GEF (Guanine nucleotide exchange factor) play in ras activation?
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GEF activates ras by cuasing it to exchange GTP for GDP.
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What protein inactivates ras and how?
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GAP (GTPPase activating protein) inactivates ras by causing it to hydrolyze GTP to GDP.
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ras activates the first kinase in a cascade of ________.
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Cytoplasmic serine/threonine kinases
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What are two signal transduction pathways, besides G-protein linked and Receptor tyrosine kinases?
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Cytokine receptor (used by myeloid and lymphoid cells)
and integrin/cadherin junctional proteins (cell/matrix and cell/cell junctions) |
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What is interesting about cytokine receptor and RTK pathways?
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They can overlap at the ras-kinase cascade pathway activated by RTKs.
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What can activate transcription factors and send signals to the nucleus involving integrin receptors?
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Junctional activation of ras.
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What is the significance of a junction sending signals to the nucleus?
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The structural assembly of focal adhesions and stress fibers in cell attached to matrix plays a feedback, regulatory role by telling the cell that it is attached to matrix in teh proper location. Helps cell survive and provide permission for cell to grow and divide.
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What are two important functions of beta-catenin?
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1) helps link actin or intermediate filaments to cell-cell junctions
2) can move into nucleus and activate transcription factors the stimulate cell cycle is not bound up in junctions |
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What are two ways to prevent cytoplasmic veta-catenin from entering the nucleus and stimulating cell division?
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a) APC (cytoplasmic protein that bind catenin and gets it degraded in proteasome
b) Cell-cell junctions |
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How are the effects of integrin and cadherin junctions opposite?
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Cell-matrix junctions are permissive for cell division whereas cell-cell junctions are inhibitors of cell division.
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