cell bio 2d

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cell bio 2d
2013-02-24 21:38:10
cell bio

cell bio
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  1. what are the stages of autophagy?
    • envelopment
    • sealing
    • merging with lysosome
    • resulting residual body
  2. what is the function of ESCRT?
    bring receptors together to concentrate them and then MVB's fuse with lysosome to rid receptors (reuse them)
  3. how does cell downregulate signal?
    by bringing it in and sending them to degradation pathway
  4. how does the secretory system work?
    • cargo proteins are translocated to the ER lumen
    • in the ER, cargo fold and inserted into VTCs
    • VTCs transport cargo to Golgi, where their oligosaccharide and polypeptide chains are processed
    • motors are translocated
  5. what's the signal for proteosome?
    multiple ubiquitin attached
  6. how does ubiquitin attach to E1?
    using ATP
  7. describe the process of ubiquitin conjugation mechanism
    • using ATP, ubiquitin attached to E1, ubiquitin-acitivating enzyme
    • E2 attaches to ubiquitin and recognizes protein for degradation,
    • coupled to E3 (protein ligase) binds to prtein to be degraded, and transfers ubiquitin from E2 to protein using ATP
    • proteosome chews protein up into aa and small peptides to be recycled
  8. how do cells respond to their environment?
    each cell expresses a genetically programmed repertoire of receptors, transuction hardware and effector system
  9. how does signal transduction affect cells?
    change in gene expression, cell shape, cell movement, cell metabolism
  10. why do most stimuli react on receptors at PM?
    they cannot penetrate PM, some light, steroid hormones, gases can penetrate PM,
  11. how are receptors inactivated?
    negative feedback, inhibitory ligand binding and phosphorylation of receptor
  12. what are the two classes of signaling molecules?
    • large requiring cell surface receptors (growth factors, cell cell interactions)
    • small or hydrophobic and able to cross PM
  13. signals lead to both short term and long term effect; what are the short and long term effects?
    • short term: change in cell activity in cytoplasm (altering protein function)
    • long term: altering gene expression (can be affected by the same signaling molecule)
  14. what is the general pathway of cell receptors?
    • signal transduction (converts mechanical or chemical mechanism to specific cellular response)
    • amplification
    • feedback loops
  15. what is the effector of seven-helix?
    trimeric G protein
  16. what is the effector of receptor tyrosine kinase and cytokine?
    tyrosine phosphorylation
  17. what is the effector of receptro guanylyl cyclase?
  18. how does receptors transfer signal?
    by conformational change or clustering to activate each other
  19. what are the three major classes of cell surface receptors?
    • ion channel linked receptors
    • G-protein linked receptors
    • enzyme linked receptors
  20. what are the characteristics of seven helix receptor?
    • use trimeric G-proteins to relay signal
    • largest family of receptors; very ancient
    • drug targets
    • structurally similar to rhodopsin
    • olfactory neurons and sight associated with this kind of receptors
  21. where does rod photoreceptors process light signals?
    in their outer segments
  22. how is rhodopsin activated?
    light binding to retinal will activate transducin, a heterotrimeric G protein
  23. what promotes the exchange of GTP for GDP, activating the G protein?
    ligand binding
  24. what is the role of alpha and gamma subunits of trimeric g protein?
    • alpha and gamma both have tails anchored on PM, alpha is regulated by GAP and GEF (activate and inactivate it)
    • alpha and beta subunits are activated by GTP binding
  25. how is the G protein coupled receptors activated?
    • ligand binds to receptor (changes in conformation)
    • G-protein binds to G protein coupled receptor, which exchange GTP for GDP (subunits separate)
  26. what activates ATP bound protein?
    • ATP (protein kinase turns it on)
    • protein phosphatase dephosphorylates turns it off
  27. how to activate and inactivate signaling by GTP binding?
    GTP bound is on, GTP hydrolysis is off
  28. what are the molecular switches that activate and inactivate monomeric proteins?
    • GAPs induces hydrolysis of GTP (inactivating)
    • GEFs are activating
  29. describe signaling amplification in the retina
    • one rhodopsin molecule absorbs one photon
    • G protein (transducin) activated
    • cyclic GMP phosphodiesterase activated
    • Na channels close (change in membrane potential
    • signal to brain
  30. what terminates G protein activation and causes reassociation of trimer?
    GTPase of alpha subunit
  31. what are the different receptor signaling types?
    • endocrine (through blood stream)
    • paracrine (close contact with another cell)
    • contact dependent (regulating self)
    • snaptic (neuronal )
  32. what are the signaling molecules?
    • ligands (change shape and activity)
    • small molecules (lipophilic-intracellular receptors in cytosol or nucleus which bind to transcription factors)
  33. can steroid hormones cross membranes?
    yes, binds directly to nuclear receptors, influencing transcription, all made from cholesterol
  34. what are the different types of steroid hormones?
    • cortisol
    • estradiol
    • testosterone
    • thyroxine
  35. what are the different growth factor receptors?
    • receptor tyrosine kinases
    • cytokine receptors
    • receptor serine/threonine kinases
  36. what does ligand binding do in receptor tyrosine kinases?
    induces dimerization and activation
  37. EGF binding does what to an autoinhibited monomer?
    ligand binding opens extracellular domains
  38. what is a SH2 protein?
    • Grb2 is an example
    • bind to P-tyr motif in receptor, which binds other proteins
  39. what is the role of Ras (G protein)
    • activates MAP kinase cascade
    • GDPases as molecular switches
    • RasGAP hydrolyze GTP to GDP
    • only active when linked to PM