Exam 3 Ch 10, 11, 12 Flashcards
1
Q
What are fatty acids
A
Hydrocarbon derivatives
-carboxylic acids with hydrocarbon tails from 4 to 36 carbons long
-can be saturated or unsaturated, branched or unbranched
2
Q
Oxidation of fatty acids (to CO2 and H2O) is highly…
A
Exergonic
3
Q
most common fatty acids have ___ number of C atoms in an _____ chain of __ to __ C’s
A
even
unbranched
12 to 24
4
Q
in monosaturated fatty acids, the double bond is usually between
A
c9 and c10
5
Q
in polysaturated fatty acids
A
the double bonds are usually c 12 and c 15
double bonds seperated by a methylene group
6
Q
double bonds in general in fatty acids
A
in cis config
7
Q
describe poly unsaturated fatty acids
A
-have more than one double bond in their backbone
-omega 3 have db between c3 and c4 relative to the most distant carbon
-omega 6 have db between c6 and c7
8
Q
PUFA and human nutrition
A
-humans must obtain omega 3 PUFA a-linolenic acid (ALA) 18:3 from diet
-humans use ALA to make EPA and DHA
-the optimal diet ratio of omega6 to omega3 PUFA is between 1:1 and 4:1
9
Q
triaclyglycerols
A
simplest lipids made from fatty acids
-made of 3 fatty acids, each in ester linkage with a glycerol
-can be one kind of fatty acid or mixed of 2-3 kinds
-non polar, hydrophobic
10
Q
solubility of fatty acids
A
poor solubility in water bc of nonpolar HC chain
-increased chain length dec solubility
-dec db number dec solubility
-carboxylic acid group is polar and ionized at neutral pH
11
Q
melting points of fatty acids
A
at RT: saturated fatty acids are waxy
-unsat fatty acids are oily liquids
12
Q
triclyglycerols provide…
A
stored energy and insulation against low temp
-vertebrates store triclyglycerols as lipid droplets in fat cells
-plants store triclyglycerols in the seeds
13
Q
lipases…
A
enzymes that catalyze hydrolysis of stored triclyglycerols, releasing fatty acids for export to sites where theyre required as fuel
-fat cells and germinating seeds contain lipases
14
Q
advantages of triclyglycerols uses as stored fuels
A
-oxidation of fatty acids yields more energy
-triclyglycerols are hydrophobic and unhydrated, so the organism doesnt have to carry the extra weight of water hydration thats associated with stored polysaccharides
15
Q
partial hydrogenation
A
process that converts many of the cis db in the fatty acids to single bonds
16
Q
______________________ to aldehydes and carboxylic acids causes lipid rich food to become rancid
A
oxidative cleavage of db in unsaturated fatty acids
17
Q
effects of partial hydrogenation
A
-improves shelf life
-increases the melting temp
-converts some cis db to trans db
18
Q
trans fatty acids
A
dietary intake of trans fatty acids= cardiovasc disease
and:
-level of triaglycerols in the blood
-raise level of LDL- bad cholesterol in the blood
-lower level of HDL- good cholestreol in the blood
-inc body inflammatory response
19
Q
waxes serve as…
A
energy stores and water repellant
20
Q
biological waxes
A
esters of long chain saturated and unsat fatty acids with long chain alcohols
-have higher mp than triaglycerols
-firm consistency
21
Q
features of linoleic acid
A
-two db
-one carbox acid group
-C-C db between carbons 9 and 10
22
Q
membranes are
A
double layer of lipids that acts as a barrier to polar molecules and ions
23
Q
membrane lipids
A
-amphipathic (one end is Np, the other polar)
-hydrophobic regions associate w e/o
-hydrophilic regions associate w water
24
Q
general types of membrane lipids 3
A
-phospholipids- hydrophobic regions with 2 fatty acids joined to glycerol or sphingosene
-glycolipids- contain simple sugar or a complex oligosaccharide at the polar ends
-sterols- rigid system of 4 fused HC rings
25
glycerophospholipids are derivatives of ...
phosphodatic acid
26
glycerophospholipids
membrane lipids that have two fatty acids are attached using ester linkage to the 1st and 2nd carbons of glycerol and a highly polar or charged group is attached through phosphodiester linkage to the 3rd carbon
27
glycerol is...
prochiral
-attachment of phosphate at one end of glycerol converts it to a chiral compound
28
glycerophospholipds are named as...
derivatives of phosphodatic acid
-a phosphodiester bond joins the head group to a glycerol
-the phosphate group can bear a negative, neutral, or positive change
29
the fatty acids in glycerophospholipds
-can be wide variety
-in general contain:
c16 or c18 saturated fatty acid at c1
c18 or c20 unsat fatty acid at c2
30
ether lipids (some glycerophospholipds have ether linked fatty acids)
one of the 2 acyl chains is attached to a glycerol in ether linkage rather than ester linkage
-chain may be saturated
-may have a db between c1 and c2 as in plasmalogens
31
platelet activating factor
an ether lipid that serves as a potent molecular signal
-released from basophils
-stimulates platelet aggregation and serotonin release
-plays a role in inflammation
32
sphingolipids are a derivative of...
sphingosine
33
what are sphingolipids?
large class of membrane phospholipids and glycolipids
-they have a polar head group and 2 non polar tails
-no glycerol
-one molecule of long chain amino alcohol sphingosine or one of its derivatives
34
_________ are the structural parent of all sphingolipids
ceramides
35
what is a ceramide
-created when a fatty acid is attached in an amide linkage to the NH2 on the C2
(structure is similar to diaclyglycerol)
36
__, __, and ___ of sphingosine are structurally analogous of the 3 carbons of glycerol in glycerophospholipids
C1 , C2, and C3
37
sphingomyelins
subclass of sphingolipids that have phosphocholine or phosphoethanolamine as their polar head group
38
glycosphingolipids
have head groups with 1+ sugars connected to the OH at C1 of the ceramide moiety
(dont have a phosphate, and they occur in the outer face of plasma membranes)
39
cerebrosides
have single sugar linked to ceramide
no charge at pH 7
40
cerebrosides with galactose
are found in the plasma membrane of cells in neural tissue
41
cerebrosides with glucose
are found in the plasma membrane of cells in non neural tissues
42
globosides
glycosphingolipids with 2+ sugars, usually D glucose, D galactose, or N-acetyl-D-galactosamine
43
gangliosides
oligosaccharides as their polar head group and 1+ residue of N-acetylneuraminic acid (Neu5Ac), a sialic acid, at the termini
44
gangliosides:
1 sialic acid residue
Gm (mono)
45
gangliosides:
2 sialic acid residue
GD (di)
46
gangliosides:
3 sialic acid residue
GT (tri)
47
sphingolipids at cell surfaces are sites of...
recognition.
-they're prominent in the plasma membranes of neurons
-human blood groups are determined partly by the oligosaccharide head groups of these glycosphingolipids
48
phospholipids and sphingolipids are _____ in lysosomes
degraded.
-phospholipases of the A type remove one of the 2 fatty acids
-lysophospholipases remove the remaining fatty acid
-lysosomal enzymes catalyze the stepwise removal of sugar units of gangliosides
49
sterols have four....
fused carbon rings
50
what are sterols?
structural lipids that are in the membranes of most euk cells
51
steroid nucleus consists of ...
-four fused rings
-almost planar
-relatively rigid
52
explain cholesterol
-major sterol in animal tissue
-amphipathic
-polar head group
-NP hydrocarbon body
-membrane constituents
-similar to stigmasterol in plants and ergosterol in fungi
53
______ hormones regulate gene expression
steroid
54
bile acids
polar derivatives of cholesterol that emulsify dietary fats in the intestine to make them more readily accessible to digestive lipases
55
__________ are a parent compound of sphingolipids
ceramides
56
what are the products of phospholipase D's degradation of phospphatidylethanolamine
phosphatidate and ethanolamine
57
phosphatidylinositols and sphingosine derivatives act as.....
intracellular signals
58
phosphatidylinositol and its phosphorylated derivatives regulate...
cell structure and metabolism
59
phosphatidylinositol 4, 5 Biphosphate (PIP2)
-exists in the cytoplasmic face of plasma membranes
-serves as a reservoir of messenger molecules that release in response to extracellular signals
60
_____________ hydrolyzes PIP2 to IP3 and diaclyglycerol, which are intracellular messengers
phospholipase C
61
Inositol phospholipids serve as points of....
nucleation
62
signaling proteins bind to ____________________ in the plasma membrane to initiate the forming of multienzyme complexes at the membranes cytosol surface
(PIP3)
63
ceramide and sphingomyelin are regulators of...
protein kinases
64
ceramide/its derivatives are involved in the regulation of:
-cell division
-differentiation
-migration
-programmed cell death
65
eicosanoids
paracrine hormones, act only on cells near the point of hormone synthesis instead of being transported in the blood
66
eicosanoids are involved in:
-reproductive function
-inflammation
-forming blood clots
-regulating blood pressure
-gastric acid secretion
67
eicosanoids are derived from...
arachidonic acid
68
what are the 4 classes of eicosanoids
prostaglandins
thromboxanes
leukotrines
lipoxins
69
prostaglandins
class of eicosanoids that have a 5 carbon ring
70
prostaglandins functions
-stimulate contraction of smooth muscle of uterus
-affect blood flow to specific organs, wake/sleep cycle, hormone responsiveness
-elevate body temp
-cause inflammation/pain
71
thromboxanes
class of eicosanoids that have a 6 carbon ring with an ether
-produced by platelets AKA thrombocytes
72
thromboxanes functions
act in formation of blood clots and reduction of blood flow to site of clot
73
leukotrines
class of eicosanoids that have 3 conjugated double bonds
74
leukotrines functions
-theyre powerful biological signals
-leukotrine D4 induces the contraction of smooth muscle lining airways to the lung
75
lipoxins, and their function
class of eicosanoids that are linear and have several hydroxyl groups
-potent anti inflammatory agent
76
what are steroids
oxidized derivatives of sterols.
-dont have the alkyl chain thats attached to ring D of cholesterol
-more polar than cholesterol
-they move through the blood stream on protein carriers to target tissues
77
what are the steroids derived from cholesterol
-testosterone
-cortisol
-prednisone
-B-Estradiol
-Aldosterone
-Brassinolide
78
Vitamins A and D are...
hormone precursors
79
what are vitamins?
compounds essential to health that cant be synthesized
80
fat soluble vitamins
A, D, E, K
81
Vitamin D3 (cholecalciferol)
formed in skin from 7-deydrocholesterol, in a photochemical reaction driven by UV
-not biologically active
-converted by enzymes in the liver/kidney to calcitriol
82
what is calcitriol
hormone that regulates calcium uptake in the intestine, and calcium levels in kidney/bones
83
vitamin A1 - all trans retinol
acts in processes of development like cell growth and differentiation and vision
-can be stored for some time in the body
-can be converted enzymatically to all trans retinoic acid
84
all trans retinoic acid
retinoid hormone that acts thru a family of nuclear receptor proteins to regulate gene expression
85
carotenoids
natural products, extensive system of conjugated db's, to make strong absorption of visible light
-B carotene pigment is a source of vitamin A
86
precursors of retinoids
B Carotene and Vitamin A1
87
Vitamins E and K and the liquid quinones are
oxidation reduction cofactors
88
vitamin E
collective name for a group of lipids- the tocopherols
89
tocopherols
hydrophobic compounds, containing a substituted aromatic ring and a long isoprenoid side chain.
-associated w cell membranes, lipid deposits, and lipoproteins
-biological antioxidants
90
vitamin K
has an aromatic ring that undergoes cycle of oxidation and reduction during the formation of prothrombin
91
prothrombin
blood plasma protein essential in blood clotting
92
ubiquinone (coenzyme Q) and plastoquinone
isoprenoids.
-they function as lipophilic electron carriers in the ox-redux reactions that drive ATP synthesis in mitochondria and chloroplasts
93
dolichols
isoprenoid alcohols.
-they activate and anchor sugars to cellular membranes.
-sugar groups are used in the synthesis of complex carbs, glycolipids, and glycoproteins
-they allow attached sugars to participate in sugar transfer reactions
94
conjugated dienes
-have carbon chains with alternating single and double bonds
-allow delocalization of electrons
-compounds can be excited by light
-many natural pigments are lipidic conjugated dienes
95
eicosanoids are made from _____ and act as ______ hormones
-arachidonate
-paracrine
96
glycerophospholipids, sphingolipids, and sterols:
-insoluble in water
-spontaneously form microscopic lipid aggregates when mixed with water
97
the lipid bilayer is ____ in water
stable
98
micelles
spherical structures with amphipathic molecules arranged with hydrophobic regions in the interior, and hydrophilic head groups on the exterior.
-favored when cross-sec areas of head group is greater than the acyl side chains
99
vesicle (liposome)
forms spontaneously when a bilayer sheet folds back on itself to form a hollow sphere
100
bilayer formation
lipid aggregate in which two lipid monolayers form a 2D sheet
-favored when cross-sec areas of head group and acyl side chains are similar
101
fluid mosaic
pattern formed from individual lipid and protein units in a membrane
-the pattern can change while maintaining the permeability membrane
102
what are the functions of biological membranes
- permit shape changes that accompany cell growth and movement
-permits exocytosis, endocytosis, and cell division
-serve as molecular gatekeepers
103
transporters (membrane)
aka translocases.
move organic solutes, inorganic ions across membrane
104
receptors (membrane)
sense extracellular signals and trigger molecular changes in the cell
105
ion channels (membrane)
mediate electrical signaling between cells
106
adhesion molecules (membrane)
hold neighboring cells together
107
single membrane surrounds:
ER
golgi apparatus
lysosomes
small vesicles
108
double membrane surrounds:
nucleus
mitochondria
chloroplasts
109
membrane trafficking
membrane lipids and proteins are synthesized in the ER and move to their destination organelle or plasma membrane
110
lipids and proteins undergo covelent modification in the...
golgi apparatus
111
what changes happen during membrane trafficking
sphingolipids and cholesterol largely replace phosphatidycholine
plasma membrane lipids are asymmetrically dist between the layers of the bilayer
112
groups of membrane proteins
-receptors for extracellular signals
-transporters to carry polar or charged compounds across the PM or between organelles
-enzymes
113
posttranslational mod of membrane proteins
glycosylation and attachment of +1 lipids (which serve as hydrophobic anchors or targeting tags)
114
glycosylation
attachment of oligosaccharides to proteins
115
integral membrane proteins
firmly embedded within the lipid bilayer
116
peripheral membrane proteins
associate with the membrane through electrostatic interactions and H bonding
117
amphitropic proteins
associate reversibly with membranes (found in membranes and cytosol)
118
monotopic proteins
have small hydrophobic domains that interact with only a single leaflet of the membrane
119
bitopic proteins
span the bilayer once, extending on either surface. have a hydrophobic seq somewhere in the molecule
120
polytopic proteins
cross the membrane several times, have multiple hydrophobic seq of 20 residues, that each cross the membrane when in a-helical conformation
121
_____% of proteins in organisms are integral proteins
20-30
122
a-helical seq of 20-25 residues
is long enough to span the thickness of the lipid bilayer.
stabilized by H bonding and the hydrophobic effect
123
hydropathy index
the free energy change associated with the movement of an AA side chain from a hydrophobic environment to water
-ranges fron exergonic to endergonic
124
overall hydropathy index
estimated by summing up the free energies of transfer for all residues in the seq
125
hydropathy plot
avg hydropathy index, plotted against residue number.
window= segment of given length
hydropathy index= y axis (avg hydropathy for a window)
residue number = x axis (residue number in the middle of the window)
126
B Barrel
structural motif, 20+ transmembrane segments form B sheets that line a cylinder
-stabilized by H bonds
127
porins
proteins that allow polar solutes to cross outer membrane of gram negative bacteria
-have B barrels lining the trans membrane passage
128
B strands, B conformation
7-9 residues needed to span a membrane
alternating side chains project above and below the sheet
129
B strands of membrane proteins
-every 2nd residue in the membrane spanning segment is hydrophobic, and interacts w lipid bilayer
-aromatic side chains are commonly found at the lipid protein interface
130
__ and __ side chains serve as membrane interface anchors
Tyr , Trp
131
positive inside rule
positively charged Lys and Arg residues (in the extra membrane loop of membrane proteins) occur more commonly on the cytoplasmic face
132
acyl groups in bilayer interior
liquid order LO state
gel like state where all types of motion of individual molecules are strongly constrained
133
acyl groups in bilayer interior
liquid disordered LD state
state in which the individual hydrocarbon chains are in constant motion
134
lipids move freely in their monolayer
mobile within their monolayer.
rotation of phospholipids around their axes can occur.
phospholipids can move via lateral diffusion
both movements are rapid and random.
135
the smooth ER membrane has proteins that catalyze the...
flip flop of membrane lipids AKA transverse diffusion.
Aka flippases
136
lipids and proteins diffuse ____ in the bilayer.
laterally.
individual lipids undergo Brownian movement.
137
FRAP
fluorescence recovery after photobleaching
-the rate is a measure of the rate of lateral diffusion of lipids
138
the lipid bilayer behaves as...
a fluid, permitting the movement of lipids and proteins.
139
fatty acid composition affects membrane fluidity
-long chain saturated fatty acids tend to pack into LO phase
-kinks in unsat fatty acids favor the LD state
-short chain fatty acyl groups favor the LD state
140
sterols impact on membrane fluidity
-can interact with phospholipids that have unsat fatty acyl chains, constraining their motion
-can associate with sphingolipids, and phospholipids with long saturated fatty acyl chains, making the bilayer fluid
141
transbilayer, flip flop movement has..
large positve free energy change
142
membrane proteins facilitate the translocation of
lipid molecules
143
flippases
-catalyze translocation of amino-phospholipids phosphatidyethanolamine (PE) and phosphatidylserine (PS) from the extracellular to the cytoplasmic leaflet of the PM
144
floppases
move PM phospholipids and sterols from the cytoplasmic leaflet to the extracellular leaflet
-ATP dependent
-ABC transporter familu
145
scramblases
move any membrane phospholipid across the bilayer down its conc gradient
-not dependent on ATP, some need Ca2+
-leads to randomization of head group composition of the 2 faces of the bilayer
146
phosphatidylinositol transfer proteins
move phophatidylinositol lipids across lipid bilayers
147
hop diffusion of lipids
-lipids diffuse laterally within small regions
-movement from one region to another (hop) is rare
148
some membrane proteins can diffuse freely, others cant
membrane proteins are limited in movement by associating to form large aggregates/patches
and anchoring to internal structures
149
microdomains/rafts
clusters of cholesterol and sphingolipids that make the bilayer thicker and more ordered.
can be up to 50% of the cell surface
150
proteins must have hydrophobic helical sections long enough to..
segregate into thicker bilayer regions of rafts
151
lipid rafts are enriched in
-proteins with 2 long chain saturated fatty acids covalently attached through Cys residues
-GPI anchored proteins.
152
caveolae
specialized rafts
153
cavolin
integral protein that binds to the cytoplasmic leaflet of the PM
-it forms dimers
-associates with cholesterol rich membrane regions
-forces the bilayer to curve inward to make caveolae
154
membrane curvature is important because
curvature changes are central to the ability of membranes to undergo fusion with other membranes and still maintain continuity
155
to move phospholipids from inner leaflet to outer leaflet of PM, which enzyme?
flopppase
156
which movement of membrane phospholipids is slowest
transbilayer diffusion
157
_________ compounds can dissolve in the lipid bilayer and cross a membrane unassisted
nonpolar
158
_________ compounds and ions require membrane protein carriers to cross membrane
polar
159
simple diffusion
movement of solute from high conc to low conc
160
membrane potential, Vm
transmembrane electrical gradient, occurs when ions of opposite charges are separated by a permeable membrane
-can produce forces that opposes ion movements that inc Vm
-drives movements that reduce Vm
161
electrochemical gradient
determines direction in which a charged solute moves across a membrane
made of:
chemical gradient
electrical gradient (Vm)
162
passive transport AKA facilitated diffusion
facilitate movement down a conc gradient, increasing transport rate
163
active transport
moves substrates across membranes against a conc gradient or electrical potential
164
primary active transport
use energy provided by chemical reaction
solute accumulation is coupled to an exergonic chemical reaction
165
secondary active transport
couple uphill transport of one substrate with downhill transport of another
-endergonic transport of one solute is coupled to the exergonic flow of a different solute that was pumped uphill by primary active transport
166
transporters proteins reduce energy of activation for diffusion by
-forming noncovalent interactions with the dehydrated solute
-providing a hydrophilic transmembrane pathway
167
ion channels
provide aqueous path across membrane that inorganic ions can diffuse at very high rates
168
features of ion channels
most have a gate regulated by a signal
typically show specificity for an ion
not saturable with their ion substrate
flow stops when gate is closed or when theres no electrochemical gradient
169
whats the difference between ion channels and transporters
ion channel has a single gate
transporter has alternating gates
170
glucose transporter of erythrocytes GLUT1 mediates...
passive transport
171
glucose enters the erythrocyte by passive transport via...
GLUT1
172
GLUT1
integral membrane protein, has 12 hydrophobic segments that form 12 membrane spanning helices
-helices are amphipathic
173
glucose transport to erythrocytes
-cycles between 2 conformations:
T1= glucose binding site exposed on the outer membrane surface
T2= glucose binding site exposed on the inner surface
174
transport of glucose into myocyte by GLUT4 is regulated by...
insulin
175
chloride bicarbonate exchanger
anion exchanger essential in CO2 transport to the lungs from tissues
-passive transport system
-no net transfer of charge
176
cotransport systems
simultaneously transport 2 solutes across a membrane
177
cotransport- antiport and symport
antiport- move in opposite direction
symport- move in same direction
178
uniport system
carry only one substrate
179
active transport is thermodynamically..
unfavorable- endergonic.
must be coupled to an exergonic process
results in accumulation of solute above eq point
180
free energy change for transport of an uncharged solute
no bonds broken and change in G is zero
181
free energy change for transport of an ion
without movement of an accompanying counter ion the process is electrogonic (produces electrical potential)
182
P type ATPases undergo...
phosphorylation during their catalytic cycles
183
P type ATPases
family of cation transporters that are phosphorylated by ATP as part of transport cycle
-integral proteins with 8 or 10 predicted membrane spanning regions
-sensitive to inhibition by the transition state analog vanadate
184
Na+ K+ Atpase
animal cell antiporter for Na+ and K+
couples phosphorylation dephosphorylation of the Asp to the movement of Na+ and K+ against their electrochemical gradients
-maintains low Na+ and high K+
-essential for action potentials
185
H+ atpase
plant and fungi transporter
186
SERCA pump (sarcoplasmic ER Ca2+ ATPase)
uniporter for Ca2+ ions
187
P type ATPases
critical Asp residue in the P domain undergoes phosphorylation and dephosphorylation
188
mechanism for SERCA
each catalytic cycle moves 2 Ca2+ ions across the membrane and converts an ATP to ADP and Pi
E1 and E2 interconvert
189
V type ATPases
class of proton transporting ATPases responsible for acidifying intracellular compartments
V0 is a proton channel
V1 is the ATP binding site and ATPase activity
190
F type ATPases
catalyze uphill transmembrane passage of protons driven by ATP hydrolysis
F0 provides pathway for protons
F1 protein uses energy of ATP to drive proteins uphill
191
F type ATPases catalyze reactions in both directions
a large proton gradient can supply the energy to drive ATP synthesis
when functioning in this direction, F type ATPases are called ATP synthases
192
ABC transporters
ATP driven transporters that pump substrates across a membrane against a conc gradient
- 2 ATP binding domains and 2 trans membrane domains
193
mechanism of ABC transporters
substrates move across the membrane when 2 forms of the transporter interconvert
-this is driven by ATP hydrolysis
194
multidrug transport, MDR1
human ABC transporter with broad substrate specificity
-its encoded by the ABCB1 gene and removes toxic compounds
-creates resistance of tumors to drugs
195
Na+ glucose symporter
takes up glucose from the intestine in a process driven by the downhill flow of Na+
196
ion gradients provide energy for secondary active transport
strong thermodynamic tendency for Na+ to move into the cell provides energy needed for the transport of gluclose into cell
197
peptide ionophore called valinomycin is an antibiotic
it acts as a shuttle to carry K+ across the membrane down its conc gradient, and deflating that gradient
198
ionophores
compounds that shuttle ions across membranes
199
aquaporins
provide channels for movement of water molecules across plasma membranes
-each protein has a specific location/role
-low activation energy suggests water moves in continuous stream
-doesnt allow for passage of protons
200
ion selective channels
-allow rapid movement of ions across membranes
-not saturable
-gated in response to cellular event
201
ligand gated channels
binding of an extracellular or intracellular small molecule forces an allosteric transition in the protein, which will open or close the channel
202
voltage gated ion channels
change in the transmembrane electrical potential causes a charged protein domain to move relative to the membrane, opening or closing the channel
203
patch clamping
currents are measured through a region of the membrane surface that has only one or a few ion channel molecules
204
the structure of a K+ channel
channel is only wide enough to accommodate an unhydrated metal ion like K+
K+ passes 100000 times more easily than Na+
205
mechanism of K+ channel
polar transmembrane passage will precisely fit the K+ ion
206
what membrane will move a hydrophobic molecule from high to low conc
this wont need a transporter
-simple diffusion
207
Ion channels/transporters (the gate)
when the gate is open, ions move through ion channel at a rate thats only limited by the max rate of diffusion
208
signal tranduction
conversion of info into a chemical change
-the signal represents info thats detected by reporters
-conversion of the signal into a cellular response involves a chemical process
209
signal specificity
created by precise molecular complementarity by the signal and receptors
-mediated by weak noncovalent forces
210
signal sensitivity
results from high affinity of receptors for their ligands
211
signal amplification
results when an enzyme is activated by a receptor and catalyzes the activation of many molecules of a 2nd enzyme in an enzyme cascade
212
modular signaling
has multiple domains to recognize specific features
-this allows cells to mix and match a set of signaling molecules
213
scaffold proteins
non enzymatic proteins that bring together enzymes that interact in cascades
214
desensitization of receptor systems
receptors are no longer responsive to a signal
-occurs when a signal is present continuously
215
integration of receptor systems
ability of a system to receive multiple signals and produce a unified response
216
signaling pathways are divergent
branched rather than linear
-it occurs when a signal is present continuously
217
response localization in signaling
cells confine signaling system components to a structure to regulate processes locally
218
features of signal transduction
-signal/ligand interacts with receptor
-activated receptor interacts with cell machinery to make a second signal or change in protein activity
-cell metabolic activity changes
-transduction event ends
219
G protein coupled receptors (GPCRs)
receptors that act through a member of the guanosine nucleotide binding family
220
three parts of the signal transduction through GPCRs
-PM receptor with 7 transmembrane helical segments
-G protein that cycles from active GTP bound and inactive GDP bound forms
-an effector enzyme or ion channel in the PM thats regulated by the activated G protein
221
first messenger signal
extracellular signal that activates a receptor from outside the cell
222
second messenger signal
low MW metabolite or inorganic ion that changes in conc due to the effector enzyme
-functions to activate or inhibit downstream targets
223
adrenergic receptors
protein receptors in the PM that bind epinephrine
(4 types : a1, a2, B1, B2)
224
B-adrenergic receptors
B1 and B2 protein receptors
225
agonist (in signaling)
molecule that binds a receptor and produces effects of the natural ligand
226
antagonist (in signaling)
analog that binds the receptor and blocks the effects of the agonist including the natural ligand
227
GPCRs
span the membrane 7 times and interact with heterotrimeric G proteins
228
heterotrimeric G proteins
conserved family of signaling proteins with the subunits a, B, and γ
-a subunit is the binding site for GDP and GTP
229
the B adrenergic pathway
GPCR acts as a guanosine nucleotide exchange factor GEF
-G protein stimulates its effector, so its referred to as stimulatory G protein: Gs
230
adenylyl cyclase
integral protein in the PM that catalyzes synthesis of cAMP from ATP when associated with Gsa
231
the synthesis and hydrolysis of cAMP
cAMP activates pKA
degradation of cAMP reverses activation of pKA
232
the GTPase switch
Gsa has GTPase activity that switches Gsa to its inactive form by converting its GTP to GDP
233
cyclic AMP activates protein Kinase A
cAMP dependent protein kinase (A or pKA)= activated by cyclic AMP
-catalyzes the phosphorylation of Ser and Thr of target proteins
234
R2C2 complex
catalytically inactive, the auto-inhibitory domain of each R subunit occupies the substrate binding of each C subunit
235
cyclic AMP is an allosteric activator of pKA
binding of cAMP yields 2 active C subunits
236
displacement of an autoinhibitory domain mediates allosteric activation of many protein kinases
structure of the substrate binding in pKA is the prototype of all known protein kinases
237
consensus seq
contain the target for phosphorylation (Ser or Thr) by protein kinases
238
FRET
measures non-radiative transfer of energy from fluorescent probes attached to the protein
-to determine if 2 proteins interact and where in the cell they interact
239
measuring cAMP with FRET
-when cAMP is low, R and C subunits of pKA are associated and FRET is exhibited
-when cAMP rises, R and C subunits of pKA dissociate and FRET stops
-when pKA is inactive, Ser is not phosphorylated and FRET is not observed
-when pKA is active, the Ser is phosphorylated and FRET is observed
