final Flashcards
1
Q
what gives actin filaments polarity
A
actin filaments have same polarization give polarity
2
Q
how are MF dynamic
A
by assembling/ itself
3
Q
is actin an atpase
A
yes
4
Q
what reflects polarity of MF
A
more rapid addition of G actin at the positive end
5
Q
what happens after G actin monomers are assembled
A
the ATP bound to them is hydrolyzed
6
Q
where is ATP actin in MF
A
growing end
7
Q
where is ADP actin on MF
A
most of MF (not growing end)
8
Q
where is there an increased rate of polymerization in MF
A
positive end
9
Q
what is tread milling
A
monomers are continuously added to the positive end and removed at the negative end
leaving it same length
10
Q
what kind of cells have lamellipodia and filopodia
A
crawling cells
11
Q
what regulates organization and behaviour of MF inside a cell
A
actin binding proteins
12
Q
how do actin binding proteins work
A
sequester monomers to regulate rate pf polymerization
13
Q
what does availability of ATP bound G actin affect
A
MF assembly
14
Q
what are 3 actin binding proteins
A
thymosin Beta 4
profilin
cofilin
15
Q
what does Thymosin beta 4 do
A
binds to ATP actin monomers and prevents them from polymerizing
16
Q
what does profilin do
A
binds to ADP G actin and catalyzes the exchange of ADP for ATP
promoting polymerization
17
Q
what does cofilin do
A
binds to ADP actin in a MF severing it and promoting depolymerization
18
Q
are actin binding proteins can cap actin filaments
A
yes
19
Q
does whether an MF can grow depend on wither their filament end his capped
A
yes
20
Q
what are 3 actin binding proteins that cap the ends
A
capping proteins
Cap Z
Tropomodulins
21
Q
what do capping proteins do
A
bind the ends of a filament to further loss/gain of subunits
22
Q
what does Cap Z do
A
binds to + end to prevent addition/loss of subunits
23
Q
what does tropomodulins do
A
binds to - ends preventing addition/loss of subunits
24
Q
can actin binding proteins sever actin filaments
A
yes
25
what are actin binding proteins that sever to actin filaments
gelsolin
cofilin
26
what does gelsolin do
breaks actin MFs and caps the newly exposed + ends, preventing further polymerization
27
what does cofilin do
filament severing protein
facilitates depolymerization
28
what kind of protein is actin
globular
29
what kind of actins are muscle specific
alpha actins
30
what happens once an actin is synthesized
folds into a globular u shaped protein that can bind ATP/ADP
31
what kind of actins are muscle specific
beta actins
32
what does G actin (globular actin) polymerize to form
MF (F-actin)
33
can actin binding proteins regulate monomers and the rate of polymerization
yes
34
what actin binding protein regulate monomers and the rate of the polymerization
formins
35
what do formins do
control assembly of actin filaments in vivo
36
what proteins cross link filaments
actin binding proteins
37
Why do filaments cross link
resist mechanical pressure
38
what actin binding protein helps filaments cross link
filamin
39
what kind of protein bundle actin filaments
actin binding protein
40
what kind of actin is prominent in actin filament bundles
alpha actin
41
why is actin bundled into filaments
enhancing rigidity
42
what link MFs to membranes
actin binding proteins
43
what nucleate new actin filaments
actin binding proteins
44
what are the most stable and least soluble cytoskeletal components
intermediate filaments
45
what kind of filament is keratin
intermediate
46
what is the major difference between MF/MT and IF
IFs can be made of many different proteins
47
what is the largest component of the cytoskeleton
MTs
48
what do MF hydrolyze
ATP
49
what do MT hydrolyze
GTP
50
what do IFs provide
mechanical strength to tissues
51
what are the main roles of each cytoskeletal component
MT: resist bending when a cell is compressed
MF: serve as contractile elements that generate tension
IF: elastic and withstand tensile forces
52
what are the supporting structures of nucleus
nuclear matrix and nuclear lamina
53
what does a nuclear matrix do (nucleoskeleton)
insoluble fibrous network that helps maintain nuclear shape
54
what does a nuclear lamina made of
thin dense meshwork of fibres
55
what kind of motor is kinesin
anterograde MT motor
56
what kind of motor is dynein
retrograde MT motor
57
what is cell contractility
shortening of muscle cells
58
what are the 2 eukaryotic motility systems
- interactions between MT and motor proteins (kinesins and dyneins)
- interactions between actin mF and myosin
59
what do motor proteins do
convert chemical energy to mechanical energy
60
what are the 3 motor proteins (and MT or MF)
kinesins - MT
Dyneins - MT
Myosins - MF
61
do any motor proteins use IF tracks
no
62
what do motors undergo cycles of
ATP hydrolysis and release of ADP and Pi and aquisition of new ATP molecule
63
what subjects motor proteins to friction
viscous cytosol
64
what are the 2 types of MT
cytoplasmic MT
Axonemal MT
65
what is an axoneme
central shaft of cilia and flagella
highly ordered bundle of Mts
66
what direction is force generated with flagella
parallel
67
what do MT provide
rigid set of tracks for transport of organelles/vesicles
68
what direction is inbound and outbound
towards - is inbound
towards + is outbound
69
what provides force needed for movement
Mt associated motor proteins that walk along MT
70
what direction is anterograde axonemal transport
towards + end (away from centrosomes)
71
what direction is retrograde axonemal transport
moves cargo towards - end
72
what is special about kinesin 14 family
are - end directed
73
what is similarity and difference between kinesins and dynein
move similar materials in opposite directions
74
what direction of force is generated by cilia
perpendicular
75
what causes MT sliding
axonemal dynein
76
what allows cilia and flagella to bend
MT sliding
77
what are primarily used in sensory structures
cilia
78
what are the two types of myosins
unconventional
conventional (type 2)
79
what direction do myosin move
most move towards the + end
type 6 is exception
80
what does a muscle fibre consist of
long thin multinucleated cell that contain many myofibrils divided into sarcomeres
81
what are sarcomeres
fundamenta contractile unit of muscle cell
82
what are sarcomeres composed of
thick filaments: staggered arrays of myosin 2
thin filaments: actin MFs with other bound proteins
83
what are thin filaments made of
tropomyosin:
troponin
84
what is troponin composed of
3 polypeptides
TnT
TnC
TnI
85
what constitute a calcium sensitive switch in sarcomeres
tropomyosin + troponin
86
what does tropomodulin
caps the - ends of the filaments to maintain stability
87
what does cap Z do
caps the + ends and attaches the MF to the Z line
88
what does the nebulin do
stabilizes and binds the thin filament ti the Z line
89
what does alpha actin do
cross links the z line to the MF keeping the thin filaments parallel
90
what does myomesin do
bundles myosin molecules
91
what is titin do
attaches the thick filaments to the Z lines and keeps thick filaments in the correct position relative to thin filaments during contractions
92
what is the sliding filament model
muscle contraction is due to thin filaments sliding past thick filaments with no change in length of either
93
what happens in the sliding filament model
myosin walks towards + end od the actin MFs (thin filaments)
because the + end is anchored at the Z line
the movement of myosin pulls actin filaments towards center
= contraction
94
what happens to cross bridges during contractions
they form and dissociate rapidly
95
what is chemotaxis
directional movement in response to graded chemical stimulus
96
what are chemoattractants
cells move towards a higher concentration of the diffusible molecules
97
what is a chemorepellent
cells move towards a lower concentration of the diffusible molecules
98
what happens in G0 phase
resting
99
what happens in g1 phase
cell growth. normal metabolism, organelles duplicate
100
what happens in S phase
DNA replication and chromosome duplication
101
what is G2 phase
cell grows and prepares for mitosis
cells contain twice the number of chromosomes
102
what happens in mitosis
segregate copies into 2 daughter cells
when cells actually divide
103
does nuclear division (mitosis) or cytoplasm division (cytokinesis) happen first
mitosis
104
what happens in prophase
chromosomal material condenses into chromosomes
cytoskeleton is disassembled
mitotic spindle is assembled
golgi and ER fragment
nuclear envelope disperses
105
what happens in prometaphase
chromosomal MT attach to kinetochores
chromosomes are moved to spindle equator
106
what happens in metaphase
chromosomes are aligned along the metaphase plate
107
what happens in anaphase
centromeres split
chromatids separate
chromosomes move to opposite spindle poles
108
what happens in telophase
chromosomes cluster at opposite spindle poles
nuclear envelope assembles around chromosome clusters
golgi and ER reform
daughter cells are formed nu cytokinesis
109
what does a ligand receptor interaction results in
conformational change
110
what are the 3 classes of signalling molecules
endocrine: produced far from target (reach via circulatory system)
paracrine: diffuasable and act locally or over short range via extracellular fluid
autocrine: act on the same cell that produces it
111
what are eicosanoids
fatty acids that regulate pain, inflammation, blood pressure, blood clotting
112
are most signalling molecules hydrophobic or hydrophilic
hydrophobic
113
what are 3 main classes of cell surface receptors
G protein coupled receptors
enzyme linked receptors (RTK)
ion channel linked receptors
114
what is the dissociation constant (kd)
the concentration of free ligands needed to produce a state in which half the receptors are occupied
115
what are agonists
drugs that activate the receptor they are bound to
116
what are antagonists
drugs that bind receptors without activating it
blocking it
117
what are second messengers
some effectors generate small molecules or ions that relay signals from one location to another
118
what do kinases do
phosphorylate
119
what do phosphatases do
dephosphorylate
120
what does phosphorylation do
changes a proteins charge and often leads to a conformational change which alters ligand binding (increasing/decreasing activity)
121
what happens to signal in divergence
one signal leads to effects on multiple pathways
122
what happens to signal in convergence
signals from multiple ligands/receptors activate same pathway
123
what happens to signal to crosstalk
signals from different pathways can affect components of multiple pathways
124
do cells sense fixed concentrations or changes in ligand concentrations
changes
125
what happens in receptor mediated endocytosis (signalling)
cells reduce density of receptors on their cell surfaces
126
what is a common method of desensitization
phosphorylation
127
what kind of G protein associates with GDP/GTP molecules
alpha G protein
128
what is desensitization
cells stop responding to the stimulus despite continued presence of the stimulus
129
what G protein is associated with K+ channel
G beta gamma
130
what causes signal termination
arrestin
131
what does receptor mediated endocytosis
removes targeted receptor from cell surface
132
what is cyclic AMP (cAMP) from
from cytosolic ATP by adenylyl cyckases, and enzyme anchored in the plasma membrane
133
what does phosphodiesterase do
degrades cAMP
134
what is the main target of cAMP
and what happens
protein kinase A (PKA)
acts as allosteric activator
regulates the separation of the regulatory and catalytic subunits
135
what does activation of kineases allow for
a significant level of signal amplification
136
what stimulates the inactivation of the enzyme system responsible for synthesis of glycogen
cAMP
137
what drives most of the effect of cAMP
PKA
138
what do AKAPs provide
scaffolding for coordinating protein-protien interactions by sequestering PKA to specific cellular locations
139
what happens to PKA when cAMP levels rise
PKA is activated
140
what does activation of phospholipase C trigger
cleavage of PIP2
which generates IP3 and DAG
141
what can lipids cleaved from membranes be used for
second messengers
142
why are cytoplasmic Ca2+ concentrations are maintained at low levels because
- Ca2+ channels in SER are kept closed
- Na+/Ca2+ antiporters and calcium ATPases in plasma membrane and SER actively transport Ca2+ out of cytosol
143
how can signalling lead to to increased cytosolic Ca2+ concentrations
voltage gated Ca2+ channels can be opened by nerve impulses
IP3 receptor channels (ligand gated Ca2+ channels) can open upon IP3
Ryanodune receptor channels (ligand-gated Ca2+ channels) are sensitive to calcium ( calcium induced calcium release)
144
what is G protein bound to when on/off
on : GTP
off: GDP
145
what do GAPs regulate
GTPases activating proteins
146
what do GDIs regulate
Guanine nucleotide dissociation inhibitors
147
what do GEFs
Guanine nucleotide exchange factors
148
what are the monomeric G proteins and what do they relate to
Ras - signal transduction
Ran - nuclear transport
Rab - tethering vesicles
Sar 1- vesicle formation
Rho - actin-binding protein regulator
149
what is Ras-MAP activated by
when a growth factor (EGF) binds the extracellular domain of RTK
150
what does Ras-GTP have a high affinity for
kinase Raf
151
what are 2 main domains in nuclear receptors
ligand binding domain
DNA binding domain
152
what is the starting material for synthesis of steroid hormones
cholesterol
153
what mediate the opening of Na+ channels
neurotransmitters
