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Cell Bio > Gap Junctions and Cell Signaling > Flashcards

Gap Junctions and Cell Signaling Flashcards

1
Q

What two types of tissue are cell junctions found to be abundant?

A

Epithelial and Connective

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2
Q

Attachments between cells are made by _____-_____ junctions

A

Cell-Cell

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3
Q

Cells are anchored onto the basal lamina through ____-____ junctions

A

Cell-Matrix

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4
Q

What are the main types of cell-cell junctions?

A

Tight Junctions
Cell-Cell Anchoring
Gap Junctions

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5
Q

What are the two forms of cell-cell anchoring junctions?

A

Adherens junctions
Desmosomes

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6
Q

What are the types of cell-matrix junctions?

A

Actin linked cell-matrix junctions
Hemidesmosomes

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7
Q

Channel forming junctions are an example of what type of cell-cell junction?

A

Gap Junction

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8
Q

What are considered the communicating junctions?

A

Gap Junctions

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9
Q

What junctions are found more lateral/apical?

A

Tight Junctions

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10
Q

What junctions are more basal/bottom of cell?

A

Desmosomes

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11
Q

Which of the following is NOT a characteristic of tight junctions?
a) Seals intercellular space from luminal environment
b) Seal is not absolute
c) Permeability varies
d) Located on basal aspect

A

D) It is located on the APICAL not the basal aspect

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12
Q

Which of the following would contain tight junctions?
a) Intestinal mucosa
b) bladder
c) respiratory tract
d) All of the above

A

d) all of the above

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13
Q

True or False
Tight junctions serve as selective permeability barriers for transcellular transport

A

False - it serves as selective barriers for PARACELLULAR transport

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14
Q

What two proteins make up tight junctions?
a) Fibronectin and laminin
b) Elastin and cadherin
c) claudin and occludin
d) none of the above

A

c) claudin and occludin

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15
Q

True or False
The lipid bilayer can transmit large forces from cell to cell and cell-ECM

A

False - it is too flimsy and needs anchoring junctions

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16
Q

Where would anchoring junctions likely be found?
a) small intestine
b) heart
c) skeletal muscle
d) epidermis
e) B, C, D

A

e) B, C, D

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17
Q

Cell-Cell Anchoring junctions rely on transmembrane adhesion proteins called:
a) Calmodulin
b) Integrins
c) Fibronectin
d) Cadherins

A

d) cadherins

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18
Q

These function as “flexible spot-welds” and form strong structural connections between cells

A

Cadherins

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19
Q

True or False
Cadherins are calcium dependent adhesion proteins

A

True

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20
Q

What junction connects one actin filament bundle in one cell to the next?

A

Adherens Junctions

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21
Q

Which of the following statements are true of adherens junctions?
a) Provide anchorage for cytoskeleton
b) Help model shape of multicellular structures
c) Guide organization of developing tissues
d) Located more basal than tight junctions
e) All of the above

A

e) all of the above

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22
Q

What junctions connect intermediate filaments in one cell to the next?

A

Desmosomes

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23
Q

True or False
Desmosomes connect actin bundle of one cell to the next

A

False - Adherens junctions connect actin bundles, Desmosomes connect intermediate filaments

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24
Q

What is the main function of desmosomes?

A

Provide mechanical strength

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25
Q

What are the cadherin proteins in desmosomes?

A

Desmoglein and Desmocollin

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26
Q

True or False
Desmosomes are likely to be found in tissue under stress/stretches (i.e. skin, muscles, intestines, stomach, bladder)

A

True

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27
Q

What junctions allow the passage of small hydrophilic molecules from cell to cell?

A

Gap Junctions

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28
Q

True or False
The gap junctions allow for a large gap between cells

A

False - the gap is narrow

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29
Q

Which of the following can pass through gap junctions?
a) Ions
b) glucose
c) second messengers
d) all of the above

A

d) all of the above

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30
Q

What type of junction is important in tissues containing electrically excitable cells?
a) Tight junctions
b) Gap junctions
c) Adherin junctions
d) Desmosomes

A

b) Gap junctions

31
Q

In what junctions do membrane proteins from adjacent cells line up to form a channel?

A

Gap Junctions

32
Q

What junctions depend on integrins?
a) Cell-Cell
b) Desmosomes
c) Cell-Matrix
d) all of the above

A

C) cell-matrix anchoring junctions

33
Q

What are the transmembrane proteins that bridge cell-matrix interactions?

34
Q

Which of the following is true of integrins?
a) Found in electrically excitable tissue
b) Ca dependent
c) Can influence almost any aspects of cell behavior
d) All of the above

A

C) Can influence almost any cell behavior
(ex: embryonic development, blood clotting, migration, proliferation, signaling, survival)

35
Q

What type of junction anchors actin-filaments in the cell to the ECM?

A

Actin linked cell-matrix junction (focal adhesion)

36
Q

True or False
Actin-Linked junctions can be small and transient OR large and durable

37
Q

What anchor intermediate filaments in a cell to the ECM?
a) Desmosomes
b) Hemidesmosomes
c) Actin filaments
d) Desmogleins

A

b) Hemidesmosomes

38
Q

True or False
Instead of desmogleins, hemidesmosomes use integrins

39
Q

What act as adhesions for epithelial cells to the basement membrane?

A

Hemidesmosomes

40
Q

Which of the following is an incorrect statement about ligands?
a) Enzymatic properties
b) Not metabolized to useful products
c) Do not act as intermediates
d) All are true statements

A

a) Enyzmatic properties - They do NOT have enzymatic properties. Their only function is to change receptor properties.

41
Q

The following are examples of first messengers except:
a) Proteins
b) Steroids
c) Neurotransmitters
d) Hormones
e) All of the above are examples

A

e) all of the above

42
Q

True or False
A receptor is a protein that receives chemical signals from only outside the cell

A

False
A receptor receives signals from outside OR inside the cell

43
Q

True or False
Effector proteins elicit cellular responses to signaling molecules

44
Q

If the cellular response to a particular signaling molecule is shape change, the ______ ______ would be enzymes that remodel the cytoskeleton.

A

effector proteins

45
Q

What is/are the ligands for cholinergic receptors?
a) Catecholamines
b) Dopamine
c) Acetylcholine
d) Epinephrine

A

c) Acetylcholine

46
Q

What is/are the ligands for adrenergic receptors?
a) Catecholamines
b) Acetylcholine
c) Dopamine
d) Norepinephrine
e) Epinephrine
f) All but B

A

f) All but B

47
Q

True or False
Nicotinic and Muscarinic are cholinergic receptors

48
Q

True or False
alpha 1, alpha 2 and beta are cholinergic receptors

A

False - they are adrenergic receptors

49
Q

Cell surface receptors are hydrophilic or hydrophobic signal molecules?

A

Hydrophobic - they can not go through the membrane so they bind to the surface.

50
Q

Intracellular receptors can be located where?
a) Cytosol
b) Cytoplasm
c) Nucleus
d) a and c
e) b and c

A

e) b and c

51
Q

All of the following are cell surface receptors EXCEPT:
a) Metabotropic
b) Ionotropic
c) Ligand Gated
d) Nuclear receptors

A

d) Nuclear receptors

52
Q

Which of the following is NOT a water-soluble second messenger?
a) Ca2+
b) DAG
c) IP3
d) cAMP

A

b) DAG - it is a lipid, therefore not water soluble

53
Q

True or false
A protein phosphatase adds a phosphate group to the protein

A

False - it removes a phosphate group, protein KINASE adds a phosphate

54
Q

What serves as a molecular switch?
a) G proteins
b) GPCR
c) Integrins
d) PIP2

A

a) G Proteins

55
Q

What is the prototype for all GPCRs?
a) Beta blockers
b) B-adrenergic
c) G proteins
d) None of the above

A

b) B-adrenergic receptors

56
Q

What activates the G-protein alpha subunit?
a) GDP
b) GTP
c) Both

A

c) Both GDP and GTP

57
Q

What is the primary role of GAPs?
a) Stimulate G-protein activation
b) Stimulates GTP-ase activity
c) Reactivates GPCR after desensitization

A

b) Stimulates GTP-ase activity - causing rapid inactivation of G protein

58
Q

What converts ATP to cAMP?
a) GTPase
b) ADP
c) Adenylate Cyclase
d) PKA

A

c) Adenylate Cyclase

59
Q

What activates PKA?
a) Binding of cAMP
b) Adenylate Cyclase
c) GTPase
d) None of the above

A

a) Binding of cAMP

60
Q

True or False
cAMP is inactivated by PDE

61
Q

What catalyzes the formation of cAMP?
a) GTP-ase
b) PKA
c) GDP/GTP
d) Adenylate Cyclase

A

d) Adenylate Cyclase

62
Q

True or False
Phosphorylation of cellular proteins by PKA cause cellular response

63
Q

Which of the following is a correct statement?
a) cAMP allosterically activates PKA
b) PKA has anabolic subunits
c) Epinephrin binds to cholinergic receptors
d) All are correct statements

A

a) cAMP allosterically activates PKA

64
Q

Which of the following is a ligand that activates Gi protein?
a) Epinephrin
b) Glucagon
c) Somatostatin
d) ACTH

A

c) Somatostatin

65
Q

All of the following are components of PIP2 pathway except:
a) PKC
b) Gi
c) Phospholipase C
d) DAG
e) IP3

66
Q

Which of the following is true regarding cAMP?
a) Formed from ATP
b) Formation is catalyzed by AC
c) Cystolic cAMP is reduced by PDE
d) All of the above

A

d) all of the above

67
Q

Which of the following is directly responsible for converting ATP into cAMP?
a) PKC
b) PKA
c) Gs
d) Adenylate Cyclase

A

d) Adenylate Cyclase

68
Q

Which of the following regulate B-adrenergic system by inactivating the pathway:
a) Low concentration of epinephrin
b) GTPase activity of G protein
c) GAPs
d) Desensitization
e) All of the above

A

e) all of the above

69
Q

What does GAP stand for?
a) G alpha Protein
b) GTPase Protein
c) GPTase Activator Protein
d) GPCR Activated Protein

A

C) GTPase Activator Protein

70
Q

Which of the following statements is correct:
a) BARK creates binding site for B-arr
b) BARK stops interaction between receptor and G-protein
c) B-arr binds to BARK
d) B-arr is involved in activation of RTK

A

a) BARK creates binding site for B-arr

71
Q

True or False
Binding of BARK stops interaction between receptor and G protein

A

False - B-arr stops interaction

72
Q

Which of the following is true?
a) GAPS catalyze reaction to active G alpha subunit
b) BARK phosphorylates receptor in order to deactivate G protein
c) Barr initiates receptor sequestration to remove the receptor via endocytosis

A

C) Barr initiates receptor sequestration to remove receptor via endocytosis

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