Cell Membrane Structure Flashcards
1
Q
dynamic, fluid structures made of lipid and protein molecules
A
cell membranes
2
Q
what are cell membranes made of
A
lipid and protein molecules
3
Q
who proposed the fluid-mosaic model
A
Singer and Nicholson (1972)
4
Q
all biological membranes are a ________
A
very thin film of lipid and protein molecules
5
Q
mainly hold the cell membrane together
A
noncovalent interactions
6
Q
what are the noncovalent interactions in the cell membrane
A
- Electrostatic forces
- cation-π interactions
- van der Waals forces
- hydrogen bonding
7
Q
cell membranes are __, __ structures
A
dynamic, fluid
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
9
Q
what does the lipid bilayer provide
A
basic fluid structure of membrane
10
Q
the lipid bilayer serves as a what
A
relatively impermeable barrier
11
Q
span the lipid bilayer and mediate nearly all of the other functions of the membrane
A
membrane proteins
12
Q
what does the membrane protein mediate
A
nearly all of other functions of membrane
13
Q
provides the basic structure for all cell membranes
A
lipid bilayer
14
Q
major lipids in cell membranes
A
- phosphoglycerides
- sphingolipids
- sterols
15
Q
the lipid bilayer is __, which means that it has both hydrophilic and hydrophobic properties
A
amphiphilic / amphipathic
16
Q
properties of the lipid bilayer
A
- self-assembly
- self-sealing property
17
Q
spontaneous bilayer formation in aqueous environment
A
self-assembly
18
Q
cell membrane will try to heal if there is breakage
A
self-sealing property
19
Q
most abundant membrane lipid
A
phospholipids
20
Q
parts of phospholipids
A
- polar phosphate-based head
- nonpolar hydrocarbon tail
21
Q
two types of phospholipid head
A
- phosphoglyceride
- sphingomyelin
22
Q
phosphoglyceride backbone
A
glycerol
23
Q
sphingomyelin backbone
A
sphingosine
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
25
how are plasmalogens linked
via ether bonds
26
two type of nonpolar hydrocarbon tail
1. saturated
2. unsaturated
27
rigid
saturated
28
kinks, preventing tight packing
unsaturated
29
kinks
cis double bond
30
Major phospholipids in mammalian plasma membranes
1. phosphatidylethanolamine (PE)
2. phosphatidylserine (PS)
3. phosphatidylcholine (PC)
4. sphingomyelin
31
- commonly found in the inner leaflet of membrane
- small head group allow tighter packing of lipids often leading to formation of curved membrane
phosphatidylethanolamine (PE)
32
where is phosphatidylethanolamine (PE) commonly found
inner leaflet
33
size of the head of phosphatidylethanolamine (PE)
small, allow for tighter packing
34
head, backbone, and tail:
phosphatidylethanolamine (PE)
head: ethanolamine
backbone: glycerol
tail: two fatty acid tail
35
head, backbone, and tail:
phosphatidylethanolamine
head: ethanolamine
backbone: glycerol
tail: two fatty acid tail
35
- located at inner leaflet
- contribute to membrane potential and cell signaling leading to apoptosis
phosphatidylserine (PS)
36
where is phosphatidylserine (PS) located
inner leaflet
37
what does phosphatidylserine (PS) contribute to
- membrane potential
- cell signaling leading to apoptosis
38
how does phosphatidylserine (PS) signal apoptosis
flips to outer leaflet which acts as signal for phagocytosis
39
head, backbone, tail:
phosphatidylserine (PS)
head: serine (negatively charged carboxyl group)
backbone: glycerol
tail: two fatty acid tail
40
- 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
phosphatidylcholine (PC)
41
where is phosphatidylcholine (PC) located
outer leaflet
42
what does phosphatidylcholine (PC) influence
membrane fluidity
43
where does phosphatidylcholine (PC) participate in
signal transduction
44
how does phosphatidylcholine (PC) participate in signal transduction
by providing a major source of lipid second messengers
45
head, backbone, tail:
phosphatidylcholine (PC)
head: choline
backbone: glycerol
tail: two fatty acid tail
46
- 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
Sphingomyelin
47
where is sphingomyelin abundant
outer leaflet
48
head, backbone, tail:
Sphingomyelin
head: phosphocholine/phosphoethanolamine
backbone: sphingosine
tail: sphingosine backbone, one lone chain of fatty acid
49
acts as 2nd hydrophobic tail of sphingomyelin
sphingosine backbone
50
- sugar alcohol with ring structure
- minor phospholipid
- found mostly in inner leaflet
- serve as precursor for signaling molecule
phosphatidylinositol (PI)
51
where is phosphatidylinositol (PI) mostly found
inner leaflet
52
phosphatidylinositol (PI) serve as a what?
precursor for signaling molecule
53
head, backbone, tail:
phosphatidylinositol (PI)
head: inostiol
backbone: glycerol
tail: two fatty acid tail
54
what does the outer leaflet consist predominantly
1. phosphatidylcholine (PC)
2. sphingomyelin
3. glycolipids
55
what does the inner leaflet consist predominantly
1. phosphatidylethanolamine
2. phosphatidylserine
3. phosphatidylinositol
56
- highly unsaturated fatty acids found at high concentration in fish oil
- showed beneficial effects
Omega-3 fatty acids
57
where are Omega-3 fatty acids incorporated primarily into (cell membrane wise)
PE and PC molecules
58
where is the Omega-3 fatty acid most notably incorporated
- brain
- retina
59
Two important fatty acids
1. eicosapentaenoic acid (EPA)
2. docosahexaenoic acid (DHA)
60
where is eicosapentaenoic acid (EPA) most beneficial
1. mood boosting
2. triglyceride support
61
where is docosahexaenoic acid (DHA) most beneficial
1. brain development
2. cognitive function
3. eye health
62
where the combination of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) most beneficial
1. heart health
2. joint health
3. immune response
63
built from sphingosine
sphingolipids
64
a long acyl chain with an amino group (NH2) and two hydroxyl groups (OH) at one en
sphingosine
65
- 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
ganglioside
66
why is ganglioside complex
presence of sialic acid
67
common form of sialic acid
NANA (n-acetylneuraminic acid)
68
where is ganglioside involved in
- cell signaling
- cell-cell communication
69
what does ganglioside modulate
- membrane proteins
- ion channels
70
what does ganglioside prevent
pathogen bonding
71
- predominantly found in myelin sheath
- contribute to nerve insulation
- cermaine backbone
- one galactose
galactocerebroside
72
structure of galactocerebroside
single galactose residue linked to ceramide (monogalactosylceramide)
73
where is galactocerebroside predominantly found
myelin sheath
74
galactocerebroside contribute to what?
nerve insulation
75
- rigid ring structure
- single polar OH group
- short nonpolar hydrocarbon tail
- intercalate between phospholipid molecules to be incorporated into biomembranes
sterol
76
structure of sterol
rigid ring
77
what does sterols do
intercalate between phospholipid molecules
78
three types of sterols
1. cholesterol
2. ergosterol
3. stigmasterol
79
sterol in animals
cholesterol
80
sterol in fungi
ergosterol
81
sterol in plants
stigmasterol
82
- play a role in maintaining stability and fluidity
- maintains rigidity at high temperatures
- prevent tight packing at low temperatures
cholesterol
83
cholesterol at high temp
maintains rigidity
84
cholesterol at low temp
prevent tight packing
85
two-dimensional fluid structure
lipid bilayer
86
- movement of lipid molecules
- rotation
- lateral diffusion
- flip-flop
membrane fluidity
87
what are the movements of lipid molecules
1. rotation
2. lateral diffusion
3. flip-flop
88
phospholipid translocators
1. floppase
2. flippase
3. scramblases
89
catalyze the ATP-dependent transport of lipids away from the cytoplasm
floppase
90
catalyze the transport of lipids toward the cytoplasm and require ATP
flippase
91
catalyze the bi-directional, non-energy-dependent transport of lipids
scramblases
92
Mediated by floppase
1. phosphatidylcholine
2. sphingomyelin
93
Mediated by flippase
1. phosphatidylethanolamine
2. phosphatidylserine
94
affected by scramblases
any lipid
95
what influences fluidity
1. composition
2. temperature
96
- shorter chain length
- more unsaturated
phase transition
97
cholesterol fills gaps between phospholipids to reduce what
permeability to low-molecular-weight solutes
98
how does cholesterol enhance membrane fluidity
disrupts interactions between fatty acids
99
cellular membranes are __ in composition
heterogenous
100
regions of the plasma membrane that accumulate cholesterol and glycolipids, and has enriched concentration of some transmembrane proteins
lipid rafts
101
what is accumulated in lipid rafts
- cholesterol
- glycolipids
102
because of their composition, what is increased in raft domains
membrane thickness
103
functionally important in the lipid bilayer
asymmetry
104
lipid symmetry is important in what?
converting extracellular signals into intracellular
105
binds to PS-rich region of the cytosolic monolayer as it requires negatively charged PS for activity
protein kinase C
106
where does protein kinase C bind to
PS-rich region
107
modified by PI 3-kinase to serve as a protein binding site
phosphatidylinositol
108
what modifies phosphatidylinositol to serve as a protein-binding site?
PI 3-kinase
109
upon activation by extracellular signals, this cleave specific phospholipid molecules, generating fragments of these molecules that act as short-lived intracellular mediators
phospholipases
110
what are the fragments generated during the cleavage of specific phospholipid molecules
1. diacylglycerol (DAG)
2. inositol trisphosphate (IP3)
111
act as 2nd messenger that activates protein kinase C
diacylglycerol (DAG)
112
- bind to receptors
- triggers release of calcium ions from ER to cytosol
inositol trisphosphate (IP3)
113
how do animals distinguish live and dead cells
phospholipid asymmetry
114
what is inactivated during apoptosis
translocase
115
what is activated in apoptosis
scramblase
116
where is membrane symmetry involved in
- protective functions
- cell-cell recognition
- cell-cell adhesion
117
give the cell membrane its characteristic functional properties
membrane proteins
118
what are the proteins in the plasma membrane
1. integral membrane (transmembrane) proteins
2. lipid-linked membrane proteins
3. peripheral membrane (membrane-associated) proteins
119
function on both sides of the bilayer
integral membrane (transmembrane) proteins
120
e.g. of integral proteins
transport proteins
121
exclusively associated with one side of the bilayer only
lipid-linked membrane proteins
122
e.g. of lipid-linked membrane proteins
signaling proteins
123
attach to membranes transiently
peripheral membrane (membrane-associated) proteins
124
e.g. of peripheral proteins
Rab GTPases
125
control the membrane localization of some signaling proteins
lipid anchors
126
what are the different lipid anchors
1. fatty acid anchor
2. isoprenyl anchor
3. GPI anchor
127
- addition of myristic acid
- anchor proteins to inner leaflet of membranes
fatty acid anchors (di ni sure)
128
- addition of isoprenoid group
- anchor proteins to inner membrane
isoprenyl anchor
129
anchor proteins to outer membrane
GPI anchors
130
what are lipid anchors for
- localization and functionality of signaling proteins
- lipid modification
131
Several functions of membrane proteins
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
e.g. of transport protien
sodium-potassium pump
133
e.g. of protein with enzymatic activity
ATP synthase
134
e.g. of signal transduction protein
GPCRs (G protein-coupled receptors)
135
e.g. of intercellular joining proteins
gap junctions
136
e.g. of cell-cell recognition proteins
MHC (major histocompatibility complex)
137
many membrane are __, or the adding of carbohydrate moeity to protein
glycosylated
138
what is added during glycosylation
oligosaccharides
139
where does glycosylation takes place
lumen of ER and the golgi body (glycoproteins) -> noncytosolic layer
140
side of the membrane that is not facing the cytosol
noncytosolic layer
141
bonds only in the noncytosolic layer
disulfide bonds
142
function of glycosylation
- stability
- cell-cell recognition and signaling
- immune function
143
- found in extracellular surface
- protective and signaling function
- influence immune response
glycocalyx
144
what can happen in membrane proteins in detergent
solubilized and purified
145
disrupt hydrophobic associations and destroy the lipid bilayer
detergents
146
detergents are what?
small amphiphilic molecules
147
two types of detergent
1. anionic
2. nonionic
148
strong anionic detergent
sodium dodecyl sulfate (SDS)
149
structure and charge of sodium dodecyl sulfate (SDS)
- long hydrophobic tail (dodecyl)
- negative charge
150
does not carry charge
nonionic
151
- nonionic
- milder
- can solubilize protein while maintaining their structrure
Triton X-100
152
structure of Triton X-100
- hydrophilic polyoxyethylene head
- hydrophobic tail
153
can be defined as the minimum concentration of the surfactant at which micelle formation takes place
Critical micelle concentration (CMC)
154
aggregate of molecules in a colloidal solution, such as those formed by detergents
micelle
