Cell Signaling
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19 terms
Terms | Definitions |
|---|---|
 What are first messengers? | the extracellular signaling molecule-the ligand-that binds to the membrane receptor, e.g., epinephrine, hormones |
| What are second messengers and 2 examples of second messengers? | involved in signaling pathways they are small, non-protein, water-soluble molecules or ions, e.g., cyclic AMP and calcium |
| What is signal amplification? | elaborate enzyme cascades, in each step the cascade the number of activated products is much greater |
| How does signal amplification benefit the cell? | elicits a coordinated response and can release hundreds of millions of molecules |
| What is the role of phosphorylation cascades in signal amplification? | activated kinase activates a different kinase and so on, at each step more and more enzymes are recruited |
| Where are the receptors involved in cell signaling located? | in the plasma membrane, e.g., an internal membrane protein OR an intracellular receptor, e.g., steroid hormone receptors |
| What is the product of adenylyl cyclase? | produces cAMP |
| How is adenylyl cyclase activity regulated? | the enzyme is modulated (positively or negatively) by different G proteins; intracellular cAMP levels go up or down depending on the summation of all the positive and negative signals on that cell |
| What reactions do protein kinases catalyze? | phosphorylation reactions: covalent transfer of phosphate group from ATP to specific amino acids of target cells, acts as an on or off switch for the target protein |
| What is the role of cAMP-dependent protein kinase in cell signaling? | to catalyze phosphorylation reactions |
| What reactions do phosphatases catalyze? | remove the phosphate groups |
| What are the subunits of Protein Kinase A? | 2 regulatory subunits and 2 catalytic subunits |
| What is the subunit composition of the active enzyme? | in the cytoplasm cAMP binds to the R subunit, R2C2 dissociates into an R dimer and 2 C monomers, C monomers catalyze phosphorylation reactions |
| What is the subunit composition of the inactive enzyme? | R2C2 |
| Summarize the steps of the G protein cycle. | 1. An activated receptor interact with the G protein, GTP replaces GDP on the alpha subunit, the G protein dissociates into alpha-GTP and a By dimer, the G protein is now on. 2. Activated G proteins interact with their target enzymes or ion channels. 3. An intrinsic GTPase activity of the alpha subunit hydrolyzes GTP to GDP, alpha-GDP and the By dimer reassociate inactivating the G protein. |
| What are examples of types of G proteins? | Gs - stimulatory G protein - stimulates adenylyl cyclase Gi - inhibitory G protein - inhibits adenylyl cyclase Golf - olfactory G protein Gt - transducin, the G protein invovled in vision |
| What are the subunits of G proteins? | alpha,beta, and gamma |
| What would happen if the G protein cycle is disrupted by mutations? (loss of function mutations) | prevent formation of stable mRNA or protein |
| What would happen if the G protein cycle is disrupted by mutations? (gain of function mutations) | e.g., activation of receptor in the absence of agonist |
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