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BIO107 - Cell and Molecular Biology > Cell Membrane Structure > Flashcards

Cell Membrane Structure Flashcards

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1
Q

dynamic, fluid structures made of lipid and protein molecules

A

cell membranes

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2
Q

what are cell membranes made of

A

lipid and protein molecules

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3
Q

who proposed the fluid-mosaic model

A

Singer and Nicholson (1972)

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4
Q

all biological membranes are a ________

A

very thin film of lipid and protein molecules

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5
Q

mainly hold the cell membrane together

A

noncovalent interactions

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6
Q

what are the noncovalent interactions in the cell membrane

A
  • Electrostatic forces
  • cation-π interactions
  • van der Waals forces
  • hydrogen bonding
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7
Q

cell membranes are __, __ structures

A

dynamic, fluid

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8
Q

provides the basic fluid structure of the membrane and serves as a relatively impermeable barrier to most water-soluble molecules

A

lipid bilayer

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9
Q

what does the lipid bilayer provide

A

basic fluid structure of membrane

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10
Q

the lipid bilayer serves as a what

A

relatively impermeable barrier

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11
Q

span the lipid bilayer and mediate nearly all of the other functions of the membrane

A

membrane proteins

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12
Q

what does the membrane protein mediate

A

nearly all of other functions of membrane

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13
Q

provides the basic structure for all cell membranes

A

lipid bilayer

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14
Q

major lipids in cell membranes

A
  1. phosphoglycerides
  2. sphingolipids
  3. sterols
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15
Q

the lipid bilayer is __, which means that it has both hydrophilic and hydrophobic properties

A

amphiphilic / amphipathic

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16
Q

properties of the lipid bilayer

A
  • self-assembly
  • self-sealing property
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17
Q

spontaneous bilayer formation in aqueous environment

A

self-assembly

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18
Q

cell membrane will try to heal if there is breakage

A

self-sealing property

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19
Q

most abundant membrane lipid

A

phospholipids

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20
Q

parts of phospholipids

A
  1. polar phosphate-based head
  2. nonpolar hydrocarbon tail
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21
Q

two types of phospholipid head

A
  1. phosphoglyceride
  2. sphingomyelin
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22
Q

phosphoglyceride backbone

A

glycerol

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23
Q

sphingomyelin backbone

A

sphingosine

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24
Q

unique class of membrane glycerophospholipids containing a fatty alcohol with a vinyl-ether bond at the sn-1 position, and enriched in polyunsaturated fatty acids at the sn-2 position of the glycerol backbone.

A

Plasmalogens

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25
Q

how are plasmalogens linked

A

via ether bonds

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26
Q

two type of nonpolar hydrocarbon tail

A
  1. saturated
  2. unsaturated
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27
Q

rigid

A

saturated

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28
Q

kinks, preventing tight packing

A

unsaturated

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29
Q

kinks

A

cis double bond

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30
Q

Major phospholipids in mammalian plasma membranes

A
  1. phosphatidylethanolamine (PE)
  2. phosphatidylserine (PS)
  3. phosphatidylcholine (PC)
  4. sphingomyelin
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31
Q
  • commonly found in the inner leaflet of membrane
  • small head group allow tighter packing of lipids often leading to formation of curved membrane
A

phosphatidylethanolamine (PE)

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32
Q

where is phosphatidylethanolamine (PE) commonly found

A

inner leaflet

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33
Q

size of the head of phosphatidylethanolamine (PE)

A

small, allow for tighter packing

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34
Q

head, backbone, and tail:
phosphatidylethanolamine (PE)

A

head: ethanolamine
backbone: glycerol
tail: two fatty acid tail

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35
Q

head, backbone, and tail:
phosphatidylethanolamine

A

head: ethanolamine
backbone: glycerol
tail: two fatty acid tail

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35
Q
  • located at inner leaflet
  • contribute to membrane potential and cell signaling leading to apoptosis
A

phosphatidylserine (PS)

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36
Q

where is phosphatidylserine (PS) located

A

inner leaflet

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37
Q

what does phosphatidylserine (PS) contribute to

A
  • membrane potential
  • cell signaling leading to apoptosis
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38
Q

how does phosphatidylserine (PS) signal apoptosis

A

flips to outer leaflet which acts as signal for phagocytosis

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39
Q

head, backbone, tail:
phosphatidylserine (PS)

A

head: serine (negatively charged carboxyl group)
backbone: glycerol
tail: two fatty acid tail

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40
Q
  • most abundant in mammalian cells
  • found in outer leaflet
  • influence membrane fluidity
  • participates in signal transduction by providing a major source of lipid second messengers
A

phosphatidylcholine (PC)

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41
Q

where is phosphatidylcholine (PC) located

A

outer leaflet

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42
Q

what does phosphatidylcholine (PC) influence

A

membrane fluidity

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43
Q

where does phosphatidylcholine (PC) participate in

A

signal transduction

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44
Q

how does phosphatidylcholine (PC) participate in signal transduction

A

by providing a major source of lipid second messengers

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45
Q

head, backbone, tail:
phosphatidylcholine (PC)

A

head: choline
backbone: glycerol
tail: two fatty acid tail

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46
Q
  • abundant in the outer leaflet of cell plasma membranes
  • with cholesterol, it forms lipid rafts which serve as platforms for proteins and protein assemblies involved in signal transduction
A

Sphingomyelin

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47
Q

where is sphingomyelin abundant

A

outer leaflet

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48
Q

head, backbone, tail:
Sphingomyelin

A

head: phosphocholine/phosphoethanolamine
backbone: sphingosine
tail: sphingosine backbone, one lone chain of fatty acid

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49
Q

acts as 2nd hydrophobic tail of sphingomyelin

A

sphingosine backbone

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50
Q
  • sugar alcohol with ring structure
  • minor phospholipid
  • found mostly in inner leaflet
  • serve as precursor for signaling molecule
A

phosphatidylinositol (PI)

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51
Q

where is phosphatidylinositol (PI) mostly found

A

inner leaflet

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52
Q

phosphatidylinositol (PI) serve as a what?

A

precursor for signaling molecule

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53
Q

head, backbone, tail:
phosphatidylinositol (PI)

A

head: inostiol
backbone: glycerol
tail: two fatty acid tail

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54
Q

what does the outer leaflet consist predominantly

A
  1. phosphatidylcholine (PC)
  2. sphingomyelin
  3. glycolipids
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55
Q

what does the inner leaflet consist predominantly

A
  1. phosphatidylethanolamine
  2. phosphatidylserine
  3. phosphatidylinositol
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56
Q
  • highly unsaturated fatty acids found at high concentration in fish oil
  • showed beneficial effects
A

Omega-3 fatty acids

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57
Q

where are Omega-3 fatty acids incorporated primarily into (cell membrane wise)

A

PE and PC molecules

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58
Q

where is the Omega-3 fatty acid most notably incorporated

A
  • brain
  • retina
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59
Q

Two important fatty acids

A
  1. eicosapentaenoic acid (EPA)
  2. docosahexaenoic acid (DHA)
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60
Q

where is eicosapentaenoic acid (EPA) most beneficial

A
  1. mood boosting
  2. triglyceride support
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61
Q

where is docosahexaenoic acid (DHA) most beneficial

A
  1. brain development
  2. cognitive function
  3. eye health
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62
Q

where the combination of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) most beneficial

A
  1. heart health
  2. joint health
  3. immune response
63
Q

built from sphingosine

A

sphingolipids

64
Q

a long acyl chain with an amino group (NH2) and two hydroxyl groups (OH) at one en

A

sphingosine

65
Q
  • subtype of sphingolipid
  • complex due to presence of sialic acid residue
  • involved in cell signaling and cell-cell communication
  • often found in terminal positions
  • modulate membrane proteins and ion channels
  • prevent pathogen bonding
A

ganglioside

66
Q

why is ganglioside complex

A

presence of sialic acid

67
Q

common form of sialic acid

A

NANA (n-acetylneuraminic acid)

68
Q

where is ganglioside involved in

A
  • cell signaling
  • cell-cell communication
69
Q

what does ganglioside modulate

A
  • membrane proteins
  • ion channels
70
Q

what does ganglioside prevent

A

pathogen bonding

71
Q
  • predominantly found in myelin sheath
  • contribute to nerve insulation
  • cermaine backbone
  • one galactose
A

galactocerebroside

72
Q

structure of galactocerebroside

A

single galactose residue linked to ceramide (monogalactosylceramide)

73
Q

where is galactocerebroside predominantly found

A

myelin sheath

74
Q

galactocerebroside contribute to what?

A

nerve insulation

75
Q
  • rigid ring structure
  • single polar OH group
  • short nonpolar hydrocarbon tail
  • intercalate between phospholipid molecules to be incorporated into biomembranes
A

sterol

76
Q

structure of sterol

A

rigid ring

77
Q

what does sterols do

A

intercalate between phospholipid molecules

78
Q

three types of sterols

A
  1. cholesterol
  2. ergosterol
  3. stigmasterol
79
Q

sterol in animals

A

cholesterol

80
Q

sterol in fungi

A

ergosterol

81
Q

sterol in plants

A

stigmasterol

82
Q
  • play a role in maintaining stability and fluidity
  • maintains rigidity at high temperatures
  • prevent tight packing at low temperatures
A

cholesterol

83
Q

cholesterol at high temp

A

maintains rigidity

84
Q

cholesterol at low temp

A

prevent tight packing

85
Q

two-dimensional fluid structure

A

lipid bilayer

86
Q
  • movement of lipid molecules
  • rotation
  • lateral diffusion
  • flip-flop
A

membrane fluidity

87
Q

what are the movements of lipid molecules

A
  1. rotation
  2. lateral diffusion
  3. flip-flop
88
Q

phospholipid translocators

A
  1. floppase
  2. flippase
  3. scramblases
89
Q

catalyze the ATP-dependent transport of lipids away from the cytoplasm

A

floppase

90
Q

catalyze the transport of lipids toward the cytoplasm and require ATP

A

flippase

91
Q

catalyze the bi-directional, non-energy-dependent transport of lipids

A

scramblases

92
Q

Mediated by floppase

A
  1. phosphatidylcholine
  2. sphingomyelin
93
Q

Mediated by flippase

A
  1. phosphatidylethanolamine
  2. phosphatidylserine
94
Q

affected by scramblases

A

any lipid

95
Q

what influences fluidity

A
  1. composition
  2. temperature
96
Q
  • shorter chain length
  • more unsaturated
A

phase transition

97
Q

cholesterol fills gaps between phospholipids to reduce what

A

permeability to low-molecular-weight solutes

98
Q

how does cholesterol enhance membrane fluidity

A

disrupts interactions between fatty acids

99
Q

cellular membranes are __ in composition

A

heterogenous

100
Q

regions of the plasma membrane that accumulate cholesterol and glycolipids, and has enriched concentration of some transmembrane proteins

A

lipid rafts

101
Q

what is accumulated in lipid rafts

A
  • cholesterol
  • glycolipids
102
Q

because of their composition, what is increased in raft domains

A

membrane thickness

103
Q

functionally important in the lipid bilayer

A

asymmetry

104
Q

lipid symmetry is important in what?

A

converting extracellular signals into intracellular

105
Q

binds to PS-rich region of the cytosolic monolayer as it requires negatively charged PS for activity

A

protein kinase C

106
Q

where does protein kinase C bind to

A

PS-rich region

107
Q

modified by PI 3-kinase to serve as a protein binding site

A

phosphatidylinositol

108
Q

what modifies phosphatidylinositol to serve as a protein-binding site?

A

PI 3-kinase

109
Q

upon activation by extracellular signals, this cleave specific phospholipid molecules, generating fragments of these molecules that act as short-lived intracellular mediators

A

phospholipases

110
Q

what are the fragments generated during the cleavage of specific phospholipid molecules

A
  1. diacylglycerol (DAG)
  2. inositol trisphosphate (IP3)
111
Q

act as 2nd messenger that activates protein kinase C

A

diacylglycerol (DAG)

112
Q
  • bind to receptors
  • triggers release of calcium ions from ER to cytosol
A

inositol trisphosphate (IP3)

113
Q

how do animals distinguish live and dead cells

A

phospholipid asymmetry

114
Q

what is inactivated during apoptosis

A

translocase

115
Q

what is activated in apoptosis

A

scramblase

116
Q

where is membrane symmetry involved in

A
  • protective functions
  • cell-cell recognition
  • cell-cell adhesion
117
Q

give the cell membrane its characteristic functional properties

A

membrane proteins

118
Q

what are the proteins in the plasma membrane

A
  1. integral membrane (transmembrane) proteins
  2. lipid-linked membrane proteins
  3. peripheral membrane (membrane-associated) proteins
119
Q

function on both sides of the bilayer

A

integral membrane (transmembrane) proteins

120
Q

e.g. of integral proteins

A

transport proteins

121
Q

exclusively associated with one side of the bilayer only

A

lipid-linked membrane proteins

122
Q

e.g. of lipid-linked membrane proteins

A

signaling proteins

123
Q

attach to membranes transiently

A

peripheral membrane (membrane-associated) proteins

124
Q

e.g. of peripheral proteins

A

Rab GTPases

125
Q

control the membrane localization of some signaling proteins

A

lipid anchors

126
Q

what are the different lipid anchors

A
  1. fatty acid anchor
  2. isoprenyl anchor
  3. GPI anchor
127
Q
  • addition of myristic acid
  • anchor proteins to inner leaflet of membranes
A

fatty acid anchors (di ni sure)

128
Q
  • addition of isoprenoid group
  • anchor proteins to inner membrane
A

isoprenyl anchor

129
Q

anchor proteins to outer membrane

A

GPI anchors

130
Q

what are lipid anchors for

A
  • localization and functionality of signaling proteins
  • lipid modification
131
Q

Several functions of membrane proteins

A
  1. transport
  2. enzymatic activity
  3. signal transduction
  4. intercellular joining
  5. cell-cell recognition
  6. attachment to the cytoskeleton and extracellular matrix (ECM)
132
Q

e.g. of transport protien

A

sodium-potassium pump

133
Q

e.g. of protein with enzymatic activity

A

ATP synthase

134
Q

e.g. of signal transduction protein

A

GPCRs (G protein-coupled receptors)

135
Q

e.g. of intercellular joining proteins

A

gap junctions

136
Q

e.g. of cell-cell recognition proteins

A

MHC (major histocompatibility complex)

137
Q

many membrane are __, or the adding of carbohydrate moeity to protein

A

glycosylated

138
Q

what is added during glycosylation

A

oligosaccharides

139
Q

where does glycosylation takes place

A

lumen of ER and the golgi body (glycoproteins) -> noncytosolic layer

140
Q

side of the membrane that is not facing the cytosol

A

noncytosolic layer

141
Q

bonds only in the noncytosolic layer

A

disulfide bonds

142
Q

function of glycosylation

A
  • stability
  • cell-cell recognition and signaling
  • immune function
143
Q
  • found in extracellular surface
  • protective and signaling function
  • influence immune response
A

glycocalyx

144
Q

what can happen in membrane proteins in detergent

A

solubilized and purified

145
Q

disrupt hydrophobic associations and destroy the lipid bilayer

A

detergents

146
Q

detergents are what?

A

small amphiphilic molecules

147
Q

two types of detergent

A
  1. anionic
  2. nonionic
148
Q

strong anionic detergent

A

sodium dodecyl sulfate (SDS)

149
Q

structure and charge of sodium dodecyl sulfate (SDS)

A
  • long hydrophobic tail (dodecyl)
  • negative charge
150
Q

does not carry charge

A

nonionic

151
Q
  • nonionic
  • milder
  • can solubilize protein while maintaining their structrure
A

Triton X-100

152
Q

structure of Triton X-100

A
  • hydrophilic polyoxyethylene head
  • hydrophobic tail
153
Q

can be defined as the minimum concentration of the surfactant at which micelle formation takes place

A

Critical micelle concentration (CMC)

154
Q

aggregate of molecules in a colloidal solution, such as those formed by detergents

A

micelle

BIO107 - Cell and Molecular Biology (9 decks)

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