Exam 1 Flashcards
(127 cards)
1
Q
Extracellular signaling molecules
A
1) are secreted or cell-surface chemical signals
2) bind to receptors
3) regulate the activity of the cell expressing the receptor
2
Q
4 forms of intercellular signaling
A
1) contact dependent
2) paracrine
3) synaptic
4) endocrine
3
Q
Contact dependent intercellular signaling
A
Extracellular signaling molecules must come in contact with the receptors
4
Q
Paracrine intercellular signaling
A
Cell releases extracellular signaling molecules into the general vicinity
5
Q
Synaptic intracellular signaling
A
Neuron to axon to target cell
6
Q
Endocrine intracellular signaling
A
Extracellular signaling molecules released in to the blood stream to take signal gar away
7
Q
Intracellular receptors
A
Mostly located near the nucleus
8
Q
Describe intracellular receptor signaling ligands
A
Must be small and hydrophobic so they can cross the lipid bilary of the cell and the nuclear membrane
9
Q
Second messengers
A
Small chemicals that serve as intercellular signaling molecules
10
Q
Examples of second messengers
A
Ca2+, cyclic AMP, IP3 (water soluble and diffuse in the cytosol)
Diacylglycerol (lipid soluble, diffuse in the plane of the plasma membrane)
11
Q
Two main molecular switches
A
1)Phosphorylation
2)GTP-binding proteins
12
Q
Protein kinases
A
A molecular switch
Adds a phosphate group to specific amino acid
13
Q
2 main types of protein kinases
A
1)Tyrosine kinase
2)Serine/threonine kinase
14
Q
Protein phosphatases
A
Molecular switches
Removes a phosphate group
15
Q
GTP-binding proteins “on” state
A
Protein bound to GTP
16
Q
GTP-binding proteins “off” state
A
Protein is bound by GDP
17
Q
Two main types of GTP-binding proteins
A
1) Large trimeric GTP-binding proteins
2) Small monomeric GTPases
18
Q
What do GAPs do to GTP-binding proteins?
A
Turns them off
19
Q
What to GEFs do to GTP-binding proteins?
A
Turns them on
20
Q
Three types of signaling complexes
A
1) Scaffold protein
2) Activated receptor
3) Phosphoinositide docking sites
21
Q
PH domain binding target
A
Phosphoinositides
22
Q
PTB domain binding target
A
Phosphorylated tyrosine
23
Q
SH2 domain binding target
A
Phosphorylated tyrosine
24
Q
SH3 domain binding target
A
Proline- rich repeats
25
Positive feedback loop
output stimulates its own production
26
Negative feedback loop
output inhibits its own production
27
How does a long delay effect a negative feedback loop?
It causes the system to oscillate
Negative feedback turns off signal, stimulus turns the signal back on.
28
How do a short delay effect a negative feedback loop?
System behaves like a detector for change
Stimulus strongly turns on signal, negative feedback loop causes it to rapidly decay, stimulus turns signal back on
29
Delayed feed-forward
Makes and inhibitory protein before the output
30
Receptor Inactivation
The receptor is help inactive even as the stimulus is there
31
Receptor Sequestration
Endocytosis receptor goes into the cell
32
Receptor Destruction
lysosome kills receptor
33
GPCR structure
Single polypeptide chain
Transverses the plasma membrane 7 times
Deep ligand binding site
34
What is needed for the receptor to truly be a GPCR?
Trimeric G-protein to relay signals
35
Active G-protein is bound to...
GTP
36
Inactive G-protein is bound to....
GDP
37
What is the role of adenylyl cyclase in cAMP signaling?
Produces cAMP
38
Stimulatory G proteins
Actives adenylyl cyclase along with Ca2+
39
Inhibitory G proteins
Inhibit adenylyl cyclase
40
cAMP phosphodiesterase
Degrades cAMP
41
PKA
serine/threonine kinase
With 4 subunits
42
IP3
Second messenger
Water soluble, diffuse through the membrane
43
DAG
Second messenger
Lipid soluble
44
Phospholipase C
PRODUCES IP3 and DAG
Activated by Gq G-protein
45
Why is Ca2+ such an important second messenger?
There is a huge concentration gradient that will drive Ca2+ into the cytosol
46
Regulatory subunits of PKA
anchor PKA to things with in the cell
has 4 Ca2+ bindng pockets
47
Catalytic subunits of PKA
Undergo a conformational change and activate
48
Calmodulin
Most important intracellular signal
Binds 4 Ca2+
Has no enzymatic activities but binds to and activates other proteins
49
Enzyme coupled receptors
Transmembrane protein
Ligand binding domain on extracellular portion
Cytosolic domain is enzymatic OR associates with an enzyme
50
What mediates signaling of RTKs
GTPases
51
Ras GEFs
stimulate the dissociation of GDP
52
Ras GAPs
Increase the rate of hydrolysis of bound GTP
53
What does Ras activate?
A MAP kinases signaling module
54
Where does phosphorylation take place on the inositol ring?
Position 3
55
PIP2
Can be cleaved by phospholipase C to generate DAG and IP3
Can be phosphorylated by PI3 kinase and serve as a docking site
56
Cells expressing Delta become
Neural cells
57
Cells expressing Notch become
Epithelial cells
58
Delta/Notch is what kind of signaling
Contact Dependent
59
What happens in the absence of Wnt?
Beta-catenin is sequestered in a degradation complex, and gets broken down
60
Is Frizzled a GPCR?
NO! There is no G-protein associated with
61
What happens in the Hedgehog pathway when Hedgehog is absent? (3)
-Patched keeps Smoothened inactive
-The Ci protein is proteolytically processed
-The cleaved tail of the Ci protein translocates to the nucleus and acts as a transcription repressor
62
Three major families of cytoskeleton components
Intermediate Filaments, Microtubules, Actin filaments
63
Actin filaments
Comprised of actin subunits and are polar
Determine shape of cell's surface
Necessary for the whole-cell locomotion
Drives pinching of one cell into two
64
Describe actin subunits
Monomeric, globular proteins with ATP-binding domain (ATP can be hydrolyzed)
65
What does it mean for a molecule to be polar
They have a plus end and a minus end.
66
Describe the plus end of actin?
Barbed and polymerize quickly
67
Describe the minus end
Pointed and polyermize slowly
68
Nucleation
When two actin molecules bind relatively weakly, but the addition of a third monomer forms a trimer that is much more stable
69
What are the three phases to the time course of polymerization?
Lag phase, Growth phase, Equilibrium/steady state
70
What is the Lag phase of polymerization?
Time taken for nucleation
71
What is the Growth phase of polymerization?
Occurs as monomers are adding to the exposed ends of the growing filament, causing filament elongation
72
What is the Equilibrium/steady state of polymerization?
Reached when the growth of the polymer balances the shrinkage of polymer
73
How can you abolish the Lag phase?
Adding premade nuclei (seed filaments)
74
What is treadmilling?
When polymerization of the + end is the same rate as depolarization of the - end
75
What does Thymosin do?
Prevent polymerization by holding the monomers like a dragon with its treasure
76
What does Profilin do?
Promote polymerization by taking subunits and add them to polymer.
77
What does ARP 2/3 complex do?
Creates structures of branching actin filaments; nucleates filaments at the minus end (cap -)
78
What does Formins do?
Creates parallel bundles of actin filaments (dimmer reaches out and grabs subunits)
79
What do Side-binding proteins do?
Stabilize and modulate interactions with other proteins (Tropomyosin)
80
What do Cap-binding proteins do?
Stabilize + or - end
81
What Cap-binding protein binds the - end?
ARP 2/3 complex
82
What Cap-binding protein binds the + end?
Cap Z
83
What does Tropomodulin do?
Bind the - end of tropomyosin-coated filaments as a capping protein
84
Cofilin
Binds along ADP-bound actin and twists and weakens it
85
Arp2/3 complex
creates dendritic branching networks of actin filaments
86
What do the Gelsolin family of proteins do?
Interact with sides of filaments and cuts them
87
What is fimbrin?
Protein that binds with actin filaments to make parallel bundles
88
What are parallele bundles?
Tight packing bundles that prevent myosin II from entering the bundle and binding
89
What does alpha- actin in do?
Bind with actin filaments to form contractile bundles
90
What are contractile bundles?
Loose packing actin bundles that allow myosin II to enter the bundle and bind
91
What to filamin dimers do?
Allow for 3D mesh/gel to form
92
What does myosin consist of?
2 heavy chains and 2 light chains
93
Which myosin chain has globular domains?
Heavy
94
What creates the myosin tail?
Long AA chain
95
Can Myosin move if ATP is bound?
NO
96
Myofibril
cylindrical structures, long chain of tiny contractile units
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Sarcomeres
Contractile
98
Protofilaments
Comprised of tubulin subunits that nis a heterodimer of Beta and Alpha tubulin
99
Beta tubulin
Has a GTP binding site that can be hydrolyze
100
Alpha tubulin
Has a GTP binding site that can not be hydrolyze
101
Stathmin
Prevents polymerization/ promotes depolymerization of microtuble
102
y-tubulin ring complex
minus end cap of microtubles
103
Centrosome
Microtubule organizing center
104
Centrioles
pair of cylindrical, barrel shaped rings of microtubules
105
Microtubule Associated Proteins
Stabilizes microtubules and mediate interactions with other components
106
MAP2
Widely spaced microtubule bundles
107
Tau
Closely packed microtubule bundles
108
Augmun
Creates branching networks of microtubules
Typically playing a major role in mitotic spindle formation
109
+TIPS
Associate with growing + ends and link microtubules to other structures
110
XMAP215
Associates with + end and accelerates /promotes polymerization
Binds to free tubulin subunits and delivers them to the + end
111
Catastrophe factors
Promote destabilization
Binds the end of microtubules and pries the protofilaments apart
112
Katanin
Cuts microtubules and promotes destabilization
113
Two types of motor proteins
Kinesin and Dynein
114
Kinesin
Motor protein that carries cargo to the PLUS end
115
Dynein
Motor protein that carries cargo to the MINUS end
116
Intermediate Filaments
made up of different elongated proteins with alpha helical domains
monomers form coiled coil dimers
Dimers form tetramers
8 tetramers form rope like filament
117
Do intermediate filaments have polarity
NO there is no structural polarity and no nucleotide binding sitesS
118
Septins
GTP binding proteins that provide scaffolding to compartmentalize membranes
119
Nuclear Laminins
Comprise a meshwork lining on the inner membrane of the nuclear envelope
120
Vimentin
Provides support in many differnt cell types
121
Keratin
Most diverse intermediate family
Provide mechanical strength to epithelial tissues
122
Neurofilaments
Present in axons of neurons
123
Plakins
Link intermediate filaments to the rest of the cytoskeleton
Can interact with other protein complexes
124
Lamellipodia actin while crawling
Actin remains stationary but undergoes treadmilling
+ ends face forward and - end attached to other actin by ARP2/3 complex
125
CDC42
Promotes polymerization of actin filaments and can activate WASp proteins
Bind ARP2/3 complexes and increase nucleation
126
RAC
Also activates WASp proteins
Increases nucleation and activates filament to create gel-like actin networks
127
Rho
Turns on formins to build parallel actin bundles
Inhibits cofilin stabilizes actin
