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Biochemistry (material for exam II) > Membrane Transport > Flashcards

Membrane Transport Flashcards

1
Q

Biological membranes are bilayers composed of what

A

amphipathic phospholipids

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2
Q

Plasma membranes permeability

A

is semi-permeable

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3
Q

Membrane transport proteins facilitate what

A

movement of specific molecules across the PM

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4
Q

The membrane proteins must have _____ domains in order to allow proper movement and regulation of ions and molecules

A

multiple

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5
Q

Transport proteins are mostly _____, ______, _____ membrane proteins

A

polytopic, transmembrane, integral

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6
Q

The plasma membrane is permeable to _________, which move via diffusion

A

lipophilic molecules

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7
Q

The plasma membrane is impermeable to _______ molecules, which need what

A

hydrophilic/polar molecules, which need a specific transport mechanism

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8
Q

Membrane proteins facilitate the transport of

A

specific molecules across the plasma membrane

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9
Q

The activity and protein levels of specific transporters determines what

A

the ionic composition of the cell

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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

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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

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12
Q

What are the two types of transport

A

Active and Passive

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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

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14
Q

Molecules move against a gradient by using biochemical energy stored in ATP is an example of what kind of transport

A

Active

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15
Q

The energy independent movement of molecules down a gradient can occur in what 2 ways

A

Simple diffusion and facilitated diffusion

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16
Q

In simple diffusion are proteins used

A

no

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17
Q

Molecules that are small, non-polar and uncharged polar diffuse freely across the membrane via what

A

simple diffusion

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18
Q

The stepper the gradient the

A

faster the simple diffusion

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19
Q

Does facilitated diffusion require proteins

A

Yes

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20
Q

Facilitated diffusion is used by

A

large and charged molecules that are unable to cross the membrane

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21
Q

In facilitated diffusion the proteins function as

A

channels or transporters

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22
Q

The unequal distribution of molecules is associated with what

A

free energy

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23
Q

____ is utilized to set up an ion gradient across a semi-permeable membrane

A

Energy

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24
Q

Ion gradients are generated by what

A

membrane transporters

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25
Q

Membrane transporters use energy from ATP and store it as what

A

free energy of the gradient

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26
Q

Energy is minimum when what

A

concentration across a semi-permeable membrane is equal

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27
Q

Free energy is proportional to

A

concentration gradient and membrane potential

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28
Q

Positive free energy means what

A

active transport

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29
Q

what are the two types of ATP utilizing proteins

A

P type ATPases and ATP binding Cassette Transporters

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30
Q

Give 4 examples of P type ATPases

A

Sodium-Potassium ATPase
Plasma Membrane Calcium ATPase (PMCA)
Sarcoplasmic reticulum calcium ATPases (SERCA)
H+-K+ ATPase

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31
Q

Give an example of ATP binding cassette transporter

A

Multi drug resistance protein

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32
Q

There are a total of how many P type ATPases

A

70

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33
Q

P type ATPases are all what kind of proteins

A

Integral

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34
Q

all P Type ATPases all use ______ to drive transport against gradient

A

ATP hydrolysis

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35
Q

ATP breaks into ___ and ____

A

ADP and phosphate

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36
Q

P type ATPases form a covalent bond with the _____ to form an enzyme- _____ intermediate

A

phosphate, phosphate

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37
Q

Where does phosphorylation on a P type ATPase occur

A

Aspartate residue

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38
Q

P type ATPases undergo ________ that facilitates the transport of ions across the membrane

A

drastic conformational changes

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39
Q

In the sodium potassium pump hydrolysis of ATP only takes place when

A

sodium and potassium are present

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40
Q

P type ATPases require what

A

Magnesium

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41
Q

In P ATPases the ATP is linked to the side chain of a specific conserved _____ residue in the ATPase to form what

A

aspartate, phosphorylaspartate

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42
Q

What is the stoichiometry of transport for the sodium potassium pump

A

3 sodium out 2 potassium in/mole ATP

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43
Q

What is the function of the sodium potassium pump

A

makes neurons and muscle cells electrically excitable, controls cell volume, drives the active transport of sugars and amino acids

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44
Q

______ %of the brain ATP is used by the Sodium pump

A

25-40%

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45
Q

Plant steroids are inhibitors of the sodium pump and work by inhibiting what

A

dephosphorylation of E2P, thus inhibiting sodium-potasium ATPase activity

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46
Q

What are two examples of sodium pump inhibitors

A

digitoxigenin and ouabain

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47
Q

Digitoxigenin and ouabain are called ______ due to their strong effect on the heart

A

Cardio steroids

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48
Q

Digitalis is a mixture of what

A

Cardiotonic steroids

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49
Q

What is Digitalis used for

A

the treatment of CHF

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50
Q

Ouabain and digitoxigenin are cardiac _____

A

glycosides

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51
Q

Digitalis inhibition of the sodium-potassium pump leads to

A

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

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52
Q

What are the tow types of calcium pumps

A

Plasma membrane calcium ATPase (PMCA) and Sarcoplasmic-endoplasmic reticulum Calcium ATPase (SERCA)

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53
Q

The PMCA’s transmembrane domain is made up of what

A

10 alpha helices

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54
Q

What is the molecular size of PMCA

A

140kDa

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55
Q

What is the function of the PMCA

A

Transports calcium from cytosol to extracellular side.

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56
Q

The PMCA maintains a calcium gradient of _______ calcium across the PM

A

10,000 fold

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57
Q

The PMCA uses ___ to pump calcium uphill

A

ATP

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58
Q

THe PMCA is stimulated by what

A

calcium binding protein calmodulin (CaM)

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59
Q

The PMCA pore is lined with what

A

Aspartate residues

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60
Q

What is the molecular size of SERCA

A

110 kDa

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61
Q

What is the function of SERCA

A

transports calcium from cytosol to ER

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62
Q

What is the structure of SERCA’s transmembrane domain

A

10 alpha helices

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63
Q

SERCA is what percentage of SR membrane protein

A

80%

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64
Q

SERCA plays a role in ____ of muscle

A

relaxation

65
Q

SERCA maintains a caclium concentration of approximately ____ in the cytoplasm compared with ____ in the sarcoplasmic reticulum

A

0.1 mM, 1.5 mM

66
Q

The transmembrane domain of SERCA has how many biding sites for calcium

A

2

67
Q

What are the calcium ions coordinated to on the transmembrane domain of SERCA

A

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
Q

Each SERCA contains a large cytoplasmic headpiece made up of how many domains and what are they called

A

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
Q

Why is SERCA smaller than PMCA

A

it does not have a C-terminus

70
Q

What is the function of the C-terminus in PMCA

A

it binds to calcium binding protein calmodulin (CaM)

71
Q

When does the membrane domain of SERCA change its conformation

A

When ADP is released, this is when eversion occurs

72
Q

The human genome has how many ABC transporter genes

A

150

73
Q

All P-type ATPases have the same fundamental mechanism explain it

A

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
Q

ABC transporters where discovered during studies of

A

tumor cells

75
Q

What is meant by multidrug-resistance

A

development of resistance to one drug had made the cells less sensitive to a range of other compounds

76
Q

what is MDR

A

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
Q

MDR has how many domains and what are there names

A

4 domains

two membrane-spanning and two ATP binding domains

78
Q

What are ABCs

A

also called ATP-binding cassettes

they are the ATP binding domains of MDRs

79
Q

In MDRs the N-terminus is what

A

is one of the membrane spanning domains

80
Q

In MDRs the C-Terminus is what

A

is one of the ATP binding domains also called the ATP-binding cassette (ABCs)

81
Q

When ATP is bound to the ABC transporters what is the conformation

A

closed form with membrane-spanning domains together

82
Q

In ABC transporters what happens after the substrate is released to the opposite face of the membrae

A

hydrolysis of ATP and the release of ADP and inorganic phosphate reset the transporter for another cycle.

83
Q

what is the major difference from Eukaryotic and prokaryotic ABC transporter function

A

prokaryotic ABC transporters often act to import specific molecules form outside the cell. while eukaryotic gneerally act to export molecules

84
Q

In ABC transporters the binding of substrate does what to ATP affinity

A

It increases the affinity for substrate

85
Q

What resets ABC transporter to its original state

A

ATP hydrolysis

86
Q

explain secondary active transport

A

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
Q

What are the three types of secondary transporters

A

Antiporters, symporters, uniporter

88
Q

what is an antiporter

A

ions move in opposite direction

type of secondary transport

89
Q

what is a symporter

A

ions move in same direction

type of secondary transport

90
Q

What is a uniporter

A

ions can move in both directions depending upon the concentration
type of secondary transport

91
Q

The sodium calcium exchanger (NCX) is an example of what

A

Antiporter

92
Q

The lactose permease is an example of what kind of transport

A

secondary

symporter

93
Q

Mitochondrial calcium transporter is an example of what kind of transport

A

secondary

uniporter

94
Q

How does lactose permease work

A

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
Q

what is the structure of lactose permease

A

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
Q

A proton from outside of the cell binds to what on the lactose permease

A

a residue ,most likely Glu 269

97
Q

Lactose is bond to the permease after what

A

after the permease is protonated

98
Q

monotopic, bitopic type I, Bitopic Type II, and polytopic are all examples of

A

integral proteins

99
Q

protein associated, acyl anchored, and phospholipid associated are all examples of

A

associated proteins

100
Q

What is the extracellular concentration of Calcium

A

1mM

101
Q

What is the intracellular concentration of calcium

A

0.0001 mM

102
Q

What is the ion fold-difference of outer to inner cellular calcium

A

> 10,000

103
Q

facilitated diffusion largely uses what type of integral protein

A

transmembrane polytopic proteins

104
Q

positive free energy means what type of transport

A

active transport

105
Q

What two factors determine if a molecule will cross the membrane

A
  • permeability of the molecule

- availability of an energy source

106
Q

The cell membrane maintains the intracellular and extracellular environments by ________ distribution of ions

A

dichotomous

107
Q

Phosphatidylserine is largely located in

A

the inner leaflet (important because it has a negative charge)

108
Q

What is the only phospholipid with a net charge

A

phosphatidylserine

109
Q

what is the equation for measuring the energy potential of uncharged molecule (chemical potential)

A

deltaG=2.303RTlog10(conc.out/conc. in)

110
Q

what is the equation for measuring the energy potential of charged molecules (Nernst equation/electrical potential)

A

deltaG= Z(61.5)log10 (conc. out/conc. in)

111
Q

a transporter forms a _____ bond with a phosphate to form an enzyme-phospate intermediate

A

covalent

112
Q

Where is the phosphorylation site of a P type ATPase

A

on a conserved aspartate residue

113
Q

Over _____ genes in human genome encode for ion channels

A

400

114
Q

Ion channels mediate

A

facilitated passive transport

115
Q

Ion channels transport ions _____ times faster than pumps

A

1000

116
Q

Ion channels are very _____ and _____ selective for ions

A

specific and highly

117
Q

enables the measurement of ion conductance via a small patch of cell membrane

A

Patch clamp technique

118
Q

what provided one of the 1st views of a single biomolecule in action

A

patch clamp technique

119
Q

What method of patch clamp technique allow one to observe membrane in its native form and the activity of the a single channel

A

Gigaohm Seal- Attached mode

120
Q

What is Gigaohm Seal- Cell attached mode

A

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
Q

What does the whole cell mode of patch clamping measure

A

the activity of channels in the entire membrane

122
Q

The excised patch mode

A

excise a patch of cell membrane and measure activity with the patch pipette

123
Q

What does Tetrodotoxin bind to

A

Na+ channels and inhibits them (basis for topical anesthetics)

124
Q

The sodium channel is made up of ___ internal repeats

A

4

125
Q

Each of the 4 repeats of sodium has how many transmembrane domains and what are they

A

6, S1,S2, S3,S4,S5,S6

126
Q

Which transmembrane domains of the sodium channel are hydrophobic

A

S1,2,3,5,6

127
Q

What is special about S4 transmembrane domain of the sodium cahnnel

A

is the voltage sensor switch,contains highly positive R or K

128
Q

Why is the potassium channel termed the shaker gene

A

because fruit flies shake violently when anesthetized with ether

129
Q

How large is the potassium channle

A

70kDa

130
Q

How large is the sodium channel

A

260kDa

131
Q

The potassium channel has how many internal repeats

A

1 repeat of S1-S6

132
Q

What are the 3 types of Ion channels

A

voltage gated
chemically gated
Mechanically gated

133
Q

Mechanically gated ion channels are found in sensory neurons that detect

A

vibration, pressure, stretch, touch, sounds, tastes, smell, heat, volume, and vision

134
Q

what transmembrane domains of the potassium channel form the pore

A

S5-S6 (location of P-loop)

135
Q

What transmembrane domains of the potassium channel form the voltage sensor

A

S1-S4 (this is responsible for opening the pore)

136
Q

How wide is the pore of the potassium channel

A

10 angstroms

137
Q

How wide is the potassium channel

A

3 angstroms

138
Q

What is the sequence of amino acids at the potassium selectivity filter

A

TVGYG

139
Q

The first _____ Amino acids for the ball and chain of the sodium and potassium voltage gated channels

A

20 amino acids

140
Q

if you length the chain of the sodium and potassium voltage gated channels then

A

it takes longer to get an inactivated state

141
Q

acetylcholine receptors open a channel that is permeable to

A

Sodium and potassium

142
Q

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

A 
Pentamer
4(2alpha,1beta,1gamma,1delta), ring
143
Q

What is the size of Actetylcholine receptor

A

268kD

144
Q

How many Ach does it take to open the acetylcholine receptor

A

2

145
Q

The Ach receptor is located

A

on the post synaptic side

146
Q

What is the size and structure of aquaporins

A

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
Q

Where are aquaporins found

A

RBCs, Kidneys, and cornea

148
Q

Special ion channels that are called cell to cell channels, responsible for direct communication

A

Gap junctions

149
Q

What are the structural features of Gap junctions

A

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
Q

What is the lumen size of a gap junction

A

about 20 angstroms

151
Q

what is the distance between gap junctions of 2 adjacent cells

A

about 35 angstroms

152
Q

What molecules can pass through gap junctions

A

small

153
Q

Physiological importance of Gap Junctions

A
  • 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
Q

Gap junctions are regulated by

A

membrane potential and hormone-induced phosphorylation

155
Q

what are 4 differences between Gap Junctions and Ion channels

A
  • 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
Q

What is the most important function of membrane transport

A

to create an AP, which is the basis for communication in the nervous system

157
Q

K+ is higher where

A

intracellularly

158
Q

Na+ is higher where

A

Extracellularly

159
Q

The Na+/K+ ATPase generates the movement of ions to establish

A

the difference in electrochemical gradient

Biochemistry (material for exam II) (10 decks)

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