Bio Exam II. 6

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DesLee26
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240457
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Bio Exam II. 6
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2013-10-13 23:29:30
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Cell Bio
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Mickle
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  1. Define a junctional interaction.
    one that can be seen as a specialized region of contact by conventional and/ or freeze-fracture electron microscopy
  2. __ and __ are involved in both nonjunctional and junctional cell-cell (__) and cell-matrix (__) contacts.
    • integrins
    • cadherins
    • cadherins
    • integrins
  3. Cadherins generally do what?
    Integrins generally do what?
    • mediate homophilic interactions
    • mediate heterophilic interactions
  4. Both cadherins and integrins do what?
    For this reason, most __ and __ are __.
    • act as transmembrane linkers adn depend on extracellular divalent cations to function
    • cell-cell and cell-matrix contacts
    • divalent-cation-dependent
  5. __ and __ can also act as __cell-cell adhesion molecules: the __ bind to carbs, while the __ bind to members of hte __.
    • selectins
    • integrins
    • heterophilic¬†
    • selectins
    • cell-binding integrins
    • IgSF
  6. What is homophilic binding?
    binding of two like molecules
  7. What is heterophilic binding?
    binding of two different molecules
  8. What is the third type of binding?
    binding through an extracellular linker molecule located in the cytoplasm; least common
  9. What are hte five types of cadheriin molecules in mammalian cells.
    • E (epithelial cells)
    • P (trophoblast, heart, lung, intestine)
    • N (nervous system)
    • R (retinal nerve and glial)
    • M (myoblasts)
  10. Cadherins: The extracellular part of the protein is __.
    The extracellular domain farthest from the membrane is thought to mediate __.
    The cytoplasmic tail interacts with te __ via a number of __, including three __ proteins. 
    __ is structurally related to __.
    • folded into five similar domains, three of which contain Ca2+ binding sites
    • cell-cell adhesion
    • actin cytoskeleton
    • intracellular attachment proteins
    • catenin
    • alpha catenin
    • vinculin
  11. What does Ca2+ do in the cadherin?
    What would happen if it weren't there?
    • form bridges between the domains
    • if it were nt there, the external portion will be the wrong shape and will be hydrolyzed
  12. What do linker proteins in the cytosol do in cadherin?
    attach the cytoplasmic portion of cadherin to actin microfilaments, leading to an influence of arrangement of actin
  13. In N-CAM, the extracellular part of the polypeptide chain in each case is __. __ connect the ends of each loop forming each __.
    • folded into five immunoglobulinlike domains (and one or two other domains called fibronectin type III repeats)
    • disulfide bonds
    • Ig-like domain
  14. Explain the extracellular portion of the N-CAM (quantity)
    How many carbs?
    N-CAMs play a huge role in __.
    • huge EC portion
    • glycoproteins
    • singlepass
    • varies
    • vertebrate development of embryos
  15. True or False:
    N-CAMs have been seen to have no cytoplasmic portions at all.
    True
  16. Binding of selectin is __. Explain the proportions of their molecules?
    • heteroophilic
    • veery large EC portions/ very small cytoplasmic portions
    • single-pass
  17. True or False:
    Selectins are not attached to the cytoskeleton.
    true
  18. The EC portion of selectins have __.
    repeat domains (one portion toward end similar to EGF
  19. The lectin domain of selectin binds to __.
    carbs
  20. Selectin is calcium- (independent or dependent).
    • dependent
    • the lectin domain won't be the right shape if the Calcium isn't there
  21. A circulating __ adheres weakly to the surface of the specialized high __ in a postcapillary venule in a lymph node. This initial adhesion, mediated by __ on the lymphocyte surface, is sufficiently weak that it enables the lymphocyte to __ the surface of the endothelial cells. The lymphocyte rapidly activates a __, mediated by an __, that enables the cell to stop __ and migrate out of the venule between the __.
    • lymphocyte
    • endothelial cells
    • E-selectin
    • roll along
    • stronger adhesion system
    • integrin
    • rolling
    • endothelial cells
  22. What is the shape of an integrin cell-surface matrix receptor.
    globular head projecting more than 20 nm from the lipid bilayer
  23. By bindign to the matrix protein outside the cell adn to the __ inside the cell, the protein serves as a __.
    • actin cytoskeleton (via the attachment proteins talin and alpha-actinin)
    • transmembrane linker
  24. The __ and __ chains are both __ and are held together by __. The __ is made initially (in the figure) as a single 140k dalton polypeptide chain, which is then __.
    • alpha beta
    • glycosylated
    • noncovalent bonds
    • alpha
    • cleaved into one small transmembrne chain and one large extracellular chain that remain held by a disulfide bond
  25. Explain the extracellular chain after cleavage.
    is folded into four divalent-cation binding domains
  26. The extracellualr aprt of the B chain contains a repeating __, where __ bonding occurs; te beta chain has a mass of about 100,000 daltons.
    • cysteine-rich region
    • intrachain disulfide bonding
  27. The integrin is a __. There are at least __ of them and are based on __.
    • heterodimer
    • 24 different heterodimers
    • binding
  28. Each chain int he integrin cell-surface matrix receptor is coated for by __.
    a different gene
  29. Binding in the integrin is dependent on what?
    It also depends on the __ what what binds.
    • divalent cations
    • alpha chains
  30. The cytosolic part of the integrin receptor is what?
    • singlepass
    • - small, cytosplasmic portion
    • - can be actin or vinculin
    • - you find actin microfilaments being bound to in the cytoplasmic skeletom
  31. Heterophilic binding can occur in integrin proteins because?
    they can bind more than one protein
  32. If any __ is exerted on adjacent cell at one end, what?
    the moleclues must be attached to the matrix
  33. Advantage of cytoskeletal attachment
    • stabilize--> cluster
    • weak attachment unless you have alot of cadherins--> stabilize whole system
  34. True or False:
    N-Cams are permanent.
    • False:
    • they can appear and siappear
  35. Why do NCAMs lose themesleves in cell migraiton of the neural test.
    they bind together, which will inhibit movemetn
  36. What must occur in order for robust cell-cell or cell-matrix adhesion to occur? Why?
    • cell-adhesion molecuels must be linked to the cytoskeleton
    • they would probably be pulled from the cell with bits of attached membrane and the holes left in the membrane would reseal
  37. Integrins have two forms. What?
    inactive and active
  38. __ have a great effect on integrins. Why?
    • talins
    • without talins, the outside is bent
  39. What is talin?
    Actvation of talin
    • one of the protiens that link to actin microfilaments
    • via a signal from either out or in, the integrins are activated

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