Membrane Transport Flashcards
1
Q
Biological membranes are bilayers composed of what
A
amphipathic phospholipids
2
Q
Plasma membranes permeability
A
is semi-permeable
3
Q
Membrane transport proteins facilitate what
A
movement of specific molecules across the PM
4
Q
The membrane proteins must have _____ domains in order to allow proper movement and regulation of ions and molecules
A
multiple
5
Q
Transport proteins are mostly _____, ______, _____ membrane proteins
A
polytopic, transmembrane, integral
6
Q
The plasma membrane is permeable to _________, which move via diffusion
A
lipophilic molecules
7
Q
The plasma membrane is impermeable to _______ molecules, which need what
A
hydrophilic/polar molecules, which need a specific transport mechanism
8
Q
Membrane proteins facilitate the transport of
A
specific molecules across the plasma membrane
9
Q
The activity and protein levels of specific transporters determines what
A
the ionic composition of the cell
10
Q
Expression of specific transporters governs
A
the biochemical/metabolic characteristics of a cell (can execute only those reactions whose substrates can be taken up
11
Q
ATP consumption per gram per minute used for signaling in the brain is equal to what
A
The energy used by a human leg muscle running a marathon
12
Q
What are the two types of transport
A
Active and Passive
13
Q
Molecules move down a concentration gradient by using energy stored in the gradient is an example of what kind of transport
A
Passive
14
Q
Molecules move against a gradient by using biochemical energy stored in ATP is an example of what kind of transport
A
Active
15
Q
The energy independent movement of molecules down a gradient can occur in what 2 ways
A
Simple diffusion and facilitated diffusion
16
Q
In simple diffusion are proteins used
A
no
17
Q
Molecules that are small, non-polar and uncharged polar diffuse freely across the membrane via what
A
simple diffusion
18
Q
The stepper the gradient the
A
faster the simple diffusion
19
Q
Does facilitated diffusion require proteins
A
Yes
20
Q
Facilitated diffusion is used by
A
large and charged molecules that are unable to cross the membrane
21
Q
In facilitated diffusion the proteins function as
A
channels or transporters
22
Q
The unequal distribution of molecules is associated with what
A
free energy
23
Q
____ is utilized to set up an ion gradient across a semi-permeable membrane
A
Energy
24
Q
Ion gradients are generated by what
A
membrane transporters
25
Membrane transporters use energy from ATP and store it as what
free energy of the gradient
26
Energy is minimum when what
concentration across a semi-permeable membrane is equal
27
Free energy is proportional to
concentration gradient and membrane potential
28
Positive free energy means what
active transport
29
what are the two types of ATP utilizing proteins
P type ATPases and ATP binding Cassette Transporters
30
Give 4 examples of P type ATPases
Sodium-Potassium ATPase
Plasma Membrane Calcium ATPase (PMCA)
Sarcoplasmic reticulum calcium ATPases (SERCA)
H+-K+ ATPase
31
Give an example of ATP binding cassette transporter
Multi drug resistance protein
32
There are a total of how many P type ATPases
70
33
P type ATPases are all what kind of proteins
Integral
34
all P Type ATPases all use ______ to drive transport against gradient
ATP hydrolysis
35
ATP breaks into ___ and ____
ADP and phosphate
36
P type ATPases form a covalent bond with the _____ to form an enzyme- _____ intermediate
phosphate, phosphate
37
Where does phosphorylation on a P type ATPase occur
Aspartate residue
38
P type ATPases undergo ________ that facilitates the transport of ions across the membrane
drastic conformational changes
39
In the sodium potassium pump hydrolysis of ATP only takes place when
sodium and potassium are present
40
P type ATPases require what
Magnesium
41
In P ATPases the ATP is linked to the side chain of a specific conserved _____ residue in the ATPase to form what
aspartate, phosphorylaspartate
42
What is the stoichiometry of transport for the sodium potassium pump
3 sodium out 2 potassium in/mole ATP
43
What is the function of the sodium potassium pump
makes neurons and muscle cells electrically excitable, controls cell volume, drives the active transport of sugars and amino acids
44
______ %of the brain ATP is used by the Sodium pump
25-40%
45
Plant steroids are inhibitors of the sodium pump and work by inhibiting what
dephosphorylation of E2P, thus inhibiting sodium-potasium ATPase activity
46
What are two examples of sodium pump inhibitors
digitoxigenin and ouabain
47
Digitoxigenin and ouabain are called ______ due to their strong effect on the heart
Cardio steroids
48
Digitalis is a mixture of what
Cardiotonic steroids
49
What is Digitalis used for
the treatment of CHF
50
Ouabain and digitoxigenin are cardiac _____
glycosides
51
Digitalis inhibition of the sodium-potassium pump leads to
increased sodium levels in the cells
reduce activity f the antiporter and sodium calcium exchanger
increase in intracellular calcium
elevated intracellular calcium leads to an increase in contractile force of the cardiac muscle
52
What are the tow types of calcium pumps
Plasma membrane calcium ATPase (PMCA) and Sarcoplasmic-endoplasmic reticulum Calcium ATPase (SERCA)
53
The PMCA's transmembrane domain is made up of what
10 alpha helices
54
What is the molecular size of PMCA
140kDa
55
What is the function of the PMCA
Transports calcium from cytosol to extracellular side.
56
The PMCA maintains a calcium gradient of _______ calcium across the PM
10,000 fold
57
The PMCA uses ___ to pump calcium uphill
ATP
58
THe PMCA is stimulated by what
calcium binding protein calmodulin (CaM)
59
The PMCA pore is lined with what
Aspartate residues
60
What is the molecular size of SERCA
110 kDa
61
What is the function of SERCA
transports calcium from cytosol to ER
62
What is the structure of SERCA's transmembrane domain
10 alpha helices
63
SERCA is what percentage of SR membrane protein
80%
64
SERCA plays a role in ____ of muscle
relaxation
65
SERCA maintains a caclium concentration of approximately ____ in the cytoplasm compared with ____ in the sarcoplasmic reticulum
0.1 mM, 1.5 mM
66
The transmembrane domain of SERCA has how many biding sites for calcium
2
67
What are the calcium ions coordinated to on the transmembrane domain of SERCA
each calcium is coordinated to seven oxygen atoms coming from a combination of side-chain glutamate, aspartate, threonine, and asparagine residues, backbone carbonyl groups, and water molecules on the transmembrane domain
68
Each SERCA contains a large cytoplasmic headpiece made up of how many domains and what are they called
3
N domain- binds to ATP nucleotide
P domain- Accepts phosphoryl group on conserved aspartate
A domain- Serves as an actuator linking changes in the N and P domains to the trans-membrane proteins
69
Why is SERCA smaller than PMCA
it does not have a C-terminus
70
What is the function of the C-terminus in PMCA
it binds to calcium binding protein calmodulin (CaM)
71
When does the membrane domain of SERCA change its conformation
When ADP is released, this is when eversion occurs
72
The human genome has how many ABC transporter genes
150
73
All P-type ATPases have the same fundamental mechanism explain it
the free energy of ATP hydrolysis drives membrane transport by means of conformational changes, which are induced by the addition and removal of a phosphoryl group at an analogous aspartate site in each protein
74
ABC transporters where discovered during studies of
tumor cells
75
What is meant by multidrug-resistance
development of resistance to one drug had made the cells less sensitive to a range of other compounds
76
what is MDR
Multidrug-resistance protein or P-glycoprotein
(glyco-because it includes a carbohydrate moiety)
MDR pumps the drug out of the cell before the drug can exert its effects
77
MDR has how many domains and what are there names
4 domains
| two membrane-spanning and two ATP binding domains
78
What are ABCs
also called ATP-binding cassettes
| they are the ATP binding domains of MDRs
79
In MDRs the N-terminus is what
is one of the membrane spanning domains
80
In MDRs the C-Terminus is what
is one of the ATP binding domains also called the ATP-binding cassette (ABCs)
81
When ATP is bound to the ABC transporters what is the conformation
closed form with membrane-spanning domains together
82
In ABC transporters what happens after the substrate is released to the opposite face of the membrae
hydrolysis of ATP and the release of ADP and inorganic phosphate reset the transporter for another cycle.
83
what is the major difference from Eukaryotic and prokaryotic ABC transporter function
prokaryotic ABC transporters often act to import specific molecules form outside the cell. while eukaryotic gneerally act to export molecules
84
In ABC transporters the binding of substrate does what to ATP affinity
It increases the affinity for substrate
85
What resets ABC transporter to its original state
ATP hydrolysis
86
explain secondary active transport
thermodynamically unfavorable flow of one species of ion against a gradient coupled to favorable flow of another species down a gradient
ATP does not directly drive them
87
What are the three types of secondary transporters
Antiporters, symporters, uniporter
88
what is an antiporter
ions move in opposite direction
| type of secondary transport
89
what is a symporter
ions move in same direction
| type of secondary transport
90
What is a uniporter
ions can move in both directions depending upon the concentration
type of secondary transport
91
The sodium calcium exchanger (NCX) is an example of what
Antiporter
92
The lactose permease is an example of what kind of transport
secondary
| symporter
93
Mitochondrial calcium transporter is an example of what kind of transport
secondary
| uniporter
94
How does lactose permease work
it uses the proton gradient across the membrane generated by the oxidation of fuel molecules to drive the uptake of lactose and other sugars against a concentration
95
what is the structure of lactose permease
protein consisting of two halves, each of which comprises 6 membrane-spanning alpha helices. The two halves are well separated and are joined by a single stretch of polypeptide. a sugar molecule lies in a pocket in the center of the protein and is accessible form a path that leads form the interior of the cell.
96
A proton from outside of the cell binds to what on the lactose permease
a residue ,most likely Glu 269
97
Lactose is bond to the permease after what
after the permease is protonated
98
monotopic, bitopic type I, Bitopic Type II, and polytopic are all examples of
integral proteins
99
protein associated, acyl anchored, and phospholipid associated are all examples of
associated proteins
100
What is the extracellular concentration of Calcium
1mM
101
What is the intracellular concentration of calcium
0.0001 mM
102
What is the ion fold-difference of outer to inner cellular calcium
>10,000
103
facilitated diffusion largely uses what type of integral protein
transmembrane polytopic proteins
104
positive free energy means what type of transport
active transport
105
What two factors determine if a molecule will cross the membrane
- permeability of the molecule
| - availability of an energy source
106
The cell membrane maintains the intracellular and extracellular environments by ________ distribution of ions
dichotomous
107
Phosphatidylserine is largely located in
the inner leaflet (important because it has a negative charge)
108
What is the only phospholipid with a net charge
phosphatidylserine
109
what is the equation for measuring the energy potential of uncharged molecule (chemical potential)
deltaG=2.303RTlog10(conc.out/conc. in)
110
what is the equation for measuring the energy potential of charged molecules (Nernst equation/electrical potential)
deltaG= Z(61.5)log10 (conc. out/conc. in)
111
a transporter forms a _____ bond with a phosphate to form an enzyme-phospate intermediate
covalent
112
Where is the phosphorylation site of a P type ATPase
on a conserved aspartate residue
113
Over _____ genes in human genome encode for ion channels
400
114
Ion channels mediate
facilitated passive transport
115
Ion channels transport ions _____ times faster than pumps
1000
116
Ion channels are very _____ and _____ selective for ions
specific and highly
117
enables the measurement of ion conductance via a small patch of cell membrane
Patch clamp technique
118
what provided one of the 1st views of a single biomolecule in action
patch clamp technique
119
What method of patch clamp technique allow one to observe membrane in its native form and the activity of the a single channel
Gigaohm Seal- Attached mode
120
What is Gigaohm Seal- Cell attached mode
a form of patch clamp technique
a pipette gently creates suction with the cell membrane so that the resistance is many gigaohms
the electrical current flowing thru the membrane is equal to that flowing thru the pipette
can detect the flow of ions thru a single channel when it is open or closed
121
What does the whole cell mode of patch clamping measure
the activity of channels in the entire membrane
122
The excised patch mode
excise a patch of cell membrane and measure activity with the patch pipette
123
What does Tetrodotoxin bind to
Na+ channels and inhibits them (basis for topical anesthetics)
124
The sodium channel is made up of ___ internal repeats
4
125
Each of the 4 repeats of sodium has how many transmembrane domains and what are they
6, S1,S2, S3,S4,S5,S6
126
Which transmembrane domains of the sodium channel are hydrophobic
S1,2,3,5,6
127
What is special about S4 transmembrane domain of the sodium cahnnel
is the voltage sensor switch,contains highly positive R or K
128
Why is the potassium channel termed the shaker gene
because fruit flies shake violently when anesthetized with ether
129
How large is the potassium channle
70kDa
130
How large is the sodium channel
260kDa
131
The potassium channel has how many internal repeats
1 repeat of S1-S6
132
What are the 3 types of Ion channels
voltage gated
chemically gated
Mechanically gated
133
Mechanically gated ion channels are found in sensory neurons that detect
vibration, pressure, stretch, touch, sounds, tastes, smell, heat, volume, and vision
134
what transmembrane domains of the potassium channel form the pore
S5-S6 (location of P-loop)
135
What transmembrane domains of the potassium channel form the voltage sensor
S1-S4 (this is responsible for opening the pore)
136
How wide is the pore of the potassium channel
10 angstroms
137
How wide is the potassium channel
3 angstroms
138
What is the sequence of amino acids at the potassium selectivity filter
TVGYG
139
The first _____ Amino acids for the ball and chain of the sodium and potassium voltage gated channels
20 amino acids
140
if you length the chain of the sodium and potassium voltage gated channels then
it takes longer to get an inactivated state
141
acetylcholine receptors open a channel that is permeable to
Sodium and potassium
142
The ligand gated ion channel is a ______ made with kinds of 4 types membrane spanning subunits arranged in the form of a ____ that creates a pore through the membrane
```
Pentamer
4(2alpha,1beta,1gamma,1delta), ring
```
143
What is the size of Actetylcholine receptor
268kD
144
How many Ach does it take to open the acetylcholine receptor
2
145
The Ach receptor is located
on the post synaptic side
146
What is the size and structure of aquaporins
24kD with 6 transmembrane alpha helical domains with hydrophilic residues lining the channel to attract H2O
Also there are positively charged residues in the channel to prohibit H+ from passing through
147
Where are aquaporins found
RBCs, Kidneys, and cornea
148
Special ion channels that are called cell to cell channels, responsible for direct communication
Gap junctions
149
What are the structural features of Gap junctions
channel is made of 12 molecules of transmemebrane protein connexin
6 connexins are packed in a hexagonal array to form 1/2 the channel called a connexon
2 connexons join end to end in the intercellular space to form a functional channel
150
What is the lumen size of a gap junction
about 20 angstroms
151
what is the distance between gap junctions of 2 adjacent cells
about 35 angstroms
152
What molecules can pass through gap junctions
small
153
Physiological importance of Gap Junctions
- Important in cardiac tissues due to it ensuring synchronous response
- Important in labor induction b/c all muscles contract in synchrony
- important in lens and bone tissue b/c they distribute nourishment
- sealed by high Calcium and H+, which protect normal cells from injured or dying cells
- regulated by membrane potential and hormone-induced phosphorylation
154
Gap junctions are regulated by
membrane potential and hormone-induced phosphorylation
155
what are 4 differences between Gap Junctions and Ion channels
- Gap junctions transverse 2 membranes
- Gap junctions connect cytoplasm to cytoplasm
- Gap junctions are synthesized by 2 different cells
- Gap junctions remain open for seconds to minutes
156
What is the most important function of membrane transport
to create an AP, which is the basis for communication in the nervous system
157
K+ is higher where
intracellularly
158
Na+ is higher where
Extracellularly
159
The Na+/K+ ATPase generates the movement of ions to establish
the difference in electrochemical gradient
