10 Flashcards
1
Q
- encloses
the cell, defines its boundaries, - maintains the essential differences between
the cytosol and the extracellular environment
A
plasma membrane
2
Q
maintain the characteristic differences
between the contents of each organelle and the cytosol
A
membrane-enclosed organelles
3
Q
Across membranes, it is established by the activities of specialized membrane proteins
- can
be used to synthesize ATP, to drive the transport of selected solutes across the
membrane, or, as in nerve and muscle cells, to produce and transmit electrical
signals
A
Ion gradients
4
Q
- plasma membrane also contains proteins that act as sensors of external signals, allowing the cell to change its behavior in response to environmental cues, including signals from other cells
A
protein sensors, or
receptors
5
Q
transfer information—rather than molecules—across the membrane
A
protein sensors, or
receptors
6
Q
provides the basic fluid structure of
the membrane and serves as a relatively impermeable barrier to the passage of
most water-soluble molecules.
A
lipid bilayer
7
Q
span the lipid bilayer and
mediate nearly all of the other functions of the membrane
A
membrane proteins
8
Q
provides the basic structure for
all cell membranes
A
Lipid Bilayer
9
Q
50% of the mass of the most
animal cell membranes
A
lipids
10
Q
All of the lipid molecules in cell
membranes are
A
amphiphilic
11
Q
they have a hydrophilic (“water-loving”) or
polar end and a hydrophobic (“water-fearing”) or nonpolar end.
A
amphiphilic
12
Q
most abundant membrane lipids
A
phospholipids
13
Q
The parts of phospholipid molecule
A
polar head group (hydrophilic) containing a phosphate group and two hydrophobic hydrocarbon tails
14
Q
containing a phosphate group
A
Head
15
Q
creates kink in the tail
A
cis-double bonds (unsaturated)
16
Q
What do cis-double bonds create
A
kink in the tail
17
Q
main phospholipids in most animal cell membranes
A
phosphoglycerides
18
Q
component of phosphoglycerides
A
- three-cardon glycerol backbone
- two long-chain fatty acids
- 3rd carbon is attached to a phosphate
group, which is linked to a head group
19
Q
the most abundant phosphoglycerides in mammalian cell membranes
A
phosphatidylethanolamine,
phosphatidylserine, and
phosphatidylcholine
20
Q
- Another important class of phospholipids
- from sphingosine
A
sphingolipids
21
Q
sphingolipids are built from
A
sphingosine
22
Q
long acyl chain with an amino group (NH2) and two hydroxyl groups (OH)
A
Sphingosine
23
Q
- most common sphingolipid
- a fatty acid tail is attached to the
amino group, and a phosphocholine
group is attached to the terminal
hydroxyl group
A
sphingomyelin
24
Q
In sphingomyelin, a ____ ___ tail is attached to the amino group, and a ____
group is attached to the terminal
hydroxyl group
A
fatty acid
phosphocholine
25
- resemble sphingolipids, but, instead
of a phosphate-linked head group, they have sugars attached
Glycolipids
26
- sterol
- contains a rigid ring structure, to which attached a single polar hydroxyl group and a
short nonpolar hydrocarbon chain
cholesterol
27
cholesterol contains?
rigid ring structure
27
what is attached on the rigid ring structure of cholesterol
single polar hydroxyl group and a short nonpolar hydrocarbon chain
28
What causes the phospholipid to form bilayers spontaneously in aqueous environments.
shape and amphiphilic nature
29
spontaneously aggregate to bury their hydrophobic tails in the interior, where they are shielded from the water, and they expose their hydrophilic heads to water.
amphiphilic molecules
30
2 ways of amphiphilic molecules to bury their hydrophobic tails in the interior, and expose their hydrophilic heads to water.
They form:
1. spherical micelles, ( tails inward)
2. double-layered sheets, or bilayers, (hydrophobic tails sandwiched between the hydrophilic head groups)
31
Parts of cholesterol
polar head groups
Cholesterol -stiffened region
More fluid region
32
same forces that drive phospholipids to form bilayers also provide a ___-___ ____
self-sealing property
33
creates a free edge with water;
because this is energetically unfavorable, the lipids tend to rearrange spontaneously to eliminate the free edge
small tear in the bilayer
34
Energetically unfavorable
Planar phospholipid bilayer with edges exposed to water
35
Energetically favorable
sealed compartment formed by phospholipid bilayer
36
only way for a bilayer to avoid having edges
closing in on itself and forming a
sealed compartment
37
are able to diffuse freely within the plane of a lipid bilayer
lipid molecules
38
have been used to measure the motion of individual lipid molecules and their components
Various techniques
39
- can be use to construct a lipid molecule
a fluorescent dye or small gold
particle attached to its polar group
40
one can modify a lipid head group to carry a ___ ___
spin label
41
Example of a “spin label"
nitroxide group (=N–O)
42
contains an unpaired electron whose spin creates a paramagnetic signal that can be
detected by electron spin resonance (ESR) spectrum
nitroxide group (=N–O)
43
phospholipid molecules in synthetic bilayers very rarely migrate from the monolayer on one side to that on the other
flip-flop”
44
lipid molecules rapidly exchange
places with their neighbors within a
monolayer
rapid lateral diffusion
45
individual lipid molecules rotate very rapidly about their ___ ___ and have flexible ____ chains
long axis
hydrocarbon
46
the lipid component of a biological membrane
two-dimensional liquid
47
constituent molecules are free to move laterally due to
two-dimensional liquid
48
catalyzes the rapid flipflop of phospholipids from one monolayer to the other
phospholipid translocators
(flippases)
49
Mobility of phospholid
1. lateral diffusion
2. Flip-flop (rarely occurs)
3. Rotation
4. Flexion
50
a change from a liquid state to a two-dimensional rigid crystalline state at a
characteristic temperature
phase transition
51
modulates the properties of lipid bilayers
cholesterol
52
When mixed with phospholipids, what does cholesterol enhances
permeability-barrier
properties
53
What does cholesterol decrease that makes the lipid less deformable
mobility of the first few CH2
groups of the chains of phospholipid molecules
54
what happens when lipid bilayer is less deformable
decreases the permeability of the bilayer to small water-molecule
55
What does cholesterol prevent
the hydrocarbon chains from
coming together and crystallizing
56
lipids usually contain 20–25-carbon-long prenyl chains
archaea
57
what does lipid contain in archaea
20–25-carbon-long prenyl chain
58
can be built from molecules with similar features but different molecular designs.
lipid bilayers
59
lipid bilayers can be built from molecules with
similar ____ but different ____
designs
features
molecular
60
more varied than those of prokaryotes and
archaea
plasma membranes of most eukaryotic cells
61
eukaryotic cell membrane has how mamy different lipid species
500-200
62
specialized membrane microdomains that
serve as to organizing centers for assembly of signaling molecules, influence membrane fluidity and trafficking of membrane proteins, and regulate different cellular processes such as neurotransmission and receptor
trafficking
lipid rafts
63
function of lipid raft
1. organizing centers for assembly of signaling molecules
2. influence membrane fluidity and trafficking of membrane proteins
3. regulate different cellular processes such as neurotransmission and receptor
trafficking
64
specific lipids come together in
separate domains
phase segregation
65
- storage of lipids
- are surrounded by a single
monolayer of phospholipids, which contains a large variety of proteins
- form rapidly when cells are exposed to high concentrations of fatty acid
lipid droplets
66
- specialized for lipid storage
- contain a giant liquid droplet
fat cells or adipocytes
67
fat cells or adipocytes contains
a giant liquid droplet
68
- neutral lipids
-do not contain hydrophilic head groups
-are exclusively hydrophobic molecules, and
therefore aggregate into 3-dimensional droplets
triacylglycerols and cholesterol esters
69
triacylglycerols and cholesterol esters aggregate into
3-dimensional droplets
70
lipid droplets are surrounded by
a single monolayer of phospholipids, which contains a large variety of proteins
71
When does lipid droplet form rapidly
when cells are exposed to high concentrations of fatty acid
72
the two ___ of the lipid bilayer have different composition
monolayers
73
- almost all of the phospholipid molecules that have choline in their head group are in the outer monolayer and almost all that contain a
terminal primary amino group are in the inner monolayer
red blood cell (erythrocyte)
74
In RBC, phospholipid molecules that have choline in their head group are in the
outer monolayer
75
In RBC,all that contain a terminal primary amino group are in the
inner monolayer
76
Outer monolayer
phosphatidylcholine and sphingomyelin
77
inner monolayer
phosphatidylethanolamine & phosphatidylserine
78
important in converting extracellular
signals into intracellular one
Lipid asymmetry
79
bind to specific lipid head groups found in the cytosolic monolayer of the lipid bilayer
many cytosolic proteins
80
Where do many cytosolic proteins bind
specific lipid head groups
81
many cytosolic proteins bind to specific lipid head groups found in the?
cytosolic monolayer of the lipid bilayer
82
Example of enzyme that binds to the cytosolic face of the plasma membrane, where phosphatidylserine is concentrated, and requires this negatively charged phospholipid for its activity
protein kinase C (PKC)
83
modified to create protein-binding sites
specific lipid head groups
84
Example of phospholipid where specific lipid head groups must first be modified to create protein-binding site
phosphatidylinositol (PI)
85
- phospholipids in the cytosolic monolayer
phosphatidylinositol (PI)
86
can add phosphate groups at distinct positions on the inositol ring, creating binding sites that recruit specific proteins from the cytosol to the membrane
lipid kinases
87
lipid kinases example
phosphoinositide 3-kinase (PI 3-kinase)
88
used in yet another way to convert extracellular signals into intracellular ones
Phospholipids in the plasma membrane
89
cleaves an inositol phospholipid in the cytosolic monolayer of the plasma membrane to generate to fragments
phospholipases C
90
What are the 2 fragments generated by phospholipases C
- one remains in the membrane and helps activate protein kinase C
- the other is released into the cytosol and stimulates the release of Ca2+ from the endoplasmic reticulum
91
What do phospholipases cleaves in the cytosolic monolayer of the plasma membrane
an inositol phospholipid
92
exploit the phospholipid asymmetry of their plasma membranes to distinguish between live and dead cells
animals
93
What do animals exploit to distinguish between live and dead cells
the phospholipid asymmetry of their plasma membranes
94
translocate from the inner monolayer to the outer monolayer when cells undergo apoptosis
phosphatidylserine
95
* sugar-containing molecules
* have most extreme asymmetry in their
membrane distribution
* found exclusively in the outer
monolayer of the lipid membrane (facing away from cytosol)
glycolipids
96
whete are glycolipids exclusively found
outer monolayer of the lipid membrane
97
results from the addition of sugar groups to the lipid molecules in the lumen of the Golgi
apparatus
asymmetric distribution of glycolipids
in the bilayer
98
what is the cause of asymmetric distribution of glycolipids in the bilayer
addition of sugar groups to the lipid molecules in the lumen of the Golgi apparatus
99
- occur in all eukaryotic cell plasma membranes, where they generally constitute about 5%
- also found in some intracellular membranes
Glycolipids
100
Glycolipids are also found in some ___ membranes
intracellular
101
the functions of glycolipids come from their ____
localization
102
glycolipids are confined to the exposed apical surface;where they may help to protect the membrane against the harsh conditions
plasma membrane of epithelial cells
103
- Charged glycolipids
- important because of their electrical effects
gangliosides
104
function in cell-recognition
glycolipids
105
Some glycolipids provide entry points for certain bacterial ___ and ___
toxins
viruses
106
- performs most of the membrane’s
specific tasks and therefore give
each type of cell membrane its
characteristic functional properties
- amphiphilic
Membrane Proteins
107
the amounts and types of proteins in
a membrane are highly ___
variable
108
extends through the lipid bilayer
transmembrane proteins
109
are located entirely in the cytosol and are attached to the cytosolic monolayer of the lipid bilayer
Other membrane proteins
110
entirely exposed at the external cell surface, being attached to the lipid bilayer only by a covalent linkage
other membrane
proteins
111
Most membrane proteins are thought to
extend across the bilayer as
(1) a single α helix,
(2) as multiple α helices, or
(3) as a rolled-up β sheet (a β barrel)
112
Other membrane transport are attached to the bilayer solely by a covalently bound ____ ___, either a fatty acid chain or a prenyl group, in the cytosolic monolayer
or (6) via an _______ linker, to phosphatidylinositol in the noncytosolic
monolayer—called a GPI anchor.
lipid chain
oligosaccharide
113
do not extend into the hydrophobic interior of
the lipid bilayer; bound to either face of the membrane by noncovalent interactions
peripheral proteins
114
can function on both side of the bilayer
or transport molecules across
transmembrane proteins
115
proteins that function on only one side of the lipid bilayer are often associated exclusively with either the ____ ____ or a
___ ____on that side
lipid monolayer
protein domain
116
- has a unique orientation in the membrane
- different functions of its cytosolic and noncytosolic domains
transmembrane protein
117
transmembrane protein has different functions of its ____ and ____ domains
cytosolic
noncytosolic
118
cytosolic and noncytosolic domains are separated by ____-____ segment of the polypeptide chain, which contact the hydrophobic area of the lipid bilayer are formed into α helix
membrane-spanning
119
polypeptide chain crosses only once
single-pass transmembrane proteins
120
the polypeptide chain crosses multiple times
multipass transmembranes
121
alternative way for the peptide bonds in the lipid bilayer to satisfy their hydrogen-bonding requirements for multiple transmembrane strands of a polypeptide chain to be arranges as a __ ____ that is rolled up into a
___
β sheet
cylinder
122
to be arranges as a β sheet that is rolled up into a cylinder
multiple transmembrane strands of a
polypeptide chain
123
are used to localize potential α – helical membrane spanning segments in a polypeptide chain
hydropathy plots
124
From hydropathy plots, it is estimated that about 30% of an organism’s proteins are
transmembrane proteins
125
Most transmembrane proteins in animal cells are
glycosylated
126
are always present on the noncytosolic side of
the membrane
oligosaccharide chains
127
Where are oligosaccharide chains always present
on the noncytosolic side of the membrane
128
are form on the noncytosolic side, where they can help stabilize either the folded structure of the polypeptide chain or its association with other polypeptide
disulfide bonds
129
where are disulfide bonds form
noncytosolic side
130
Why disulfude bonds are form on the
noncytosolic side
- help stabilize either the folded
structure of the polypeptide chain
or its association with other
polypeptide
131
extensively coat the surface of all eukaryotic cells
carbohydrates
132
What agents can solubilize membrane proteins
agents that disrupt hydrophobic associations and destroy the lipid bilayer
133
small amphiphilic molecules; more soluble in water than lipids
detergents
134
The detergent's polar side
1. charged (ionic), as in sodium
dodecyl sulfate (SDS), or
2. uncharged (nonionic), as in octylglucoside and Triton
135
surfactant concentration at which micelle formation is first seen in the solution
critical micelle concentration (CMC)
136
When mixed with membranes, the _____ ___ of
detergents bind to the hydrophobic regions of the membrane proteins, where they displace lipid molecules with a collar of detergent molecules
hydrophobic ends
137
Many membrane proteins can be solubilized and then purified in an active form by the use of ___ detergents.
mild
138
Using mild detergents , functionally ____ _____ ___ systems can be reconstituted from purified
components, providing a powerful
means of analyzing the activities of
membrane transporters, ion
channels, signaling receptors, and
so on
active membrane protein
139
small, uniformly sized patches of membrane that are surrounded by a belt of protein,
which covers the exposed edge of the bilayer to keep the patch in solution
nanodiscs
140
can be analyzed by single particle
electron microscopy techniques to
determine their structure
Proteins contained in nanodiscs
141
function as part of multicomponent complexes
membrane proteins
142
the first membrane protein complex to be
crystallized and analyzed by x-ray diffraction
photosynthetic reaction center
143
function to capture light energy and use it to pump H+ across the membrane
photosynthetic complexes (photosynthetic reaction center? Ambot kung same rana sila do)
144
membrane proteins do not ___ across the lipid bilayer
tumble (flip-flop)
145
membrane proteins do ___ about an axis perpendicular to the plane of the
bilayer
146
many membrane proteins are able to
move laterally within the membrane
lateral diffusion
147
some plasma membrane proteins
are mobile in the __ of the
membrane
plane
148
-measures lateral diffusion rates of membrane
proteins
-involves marking the membrane protein of interest with a specific fluorescent group.
fluorescence recovery after
photobleaching (FRAP)
149
Exampke that involves marking the membrane protein of interest with a specific fluorescent group.
green fluorescent protein (GFP)
150
labeling individual membrane molecules
and track their movement by video
microscopy
single-particle tracking
151
most cells ___ membrane
proteins to specific regions
confine
152
certain plasma
membrane enzymes and transport
proteins are confined to the apical
surface of the cells, whereas others
are confined to the basal and
lateral surfaces
epithelial cells
153
where are plasma membrane enzymes and transport proteins are confined to in epithelial cells
apical surface, others to the basal and
lateral surfaces
154
often essential for the function of the epithelium
asymmetric distribution of
membrane proteins
155
maintain the separation of both protein and lipid molecules
barriers set up by specific type of
intercellular junction
156
create nanoscale raft domains that function in signaling and membrane trafficking
protein-protein interactions in membranes
157
protein-protein interactions in
membranes create?
nanoscale raft
domains
158
a single cell that consists of several structurally and functionally
distinct parts covered by a continuous plasma membrane
mammalian spermatozoon
159
Its characteristic biconcave shape results from
interactions of its plasma membrane
proteins with an underlying
cytoskeleton, which consists mainly
of a meshwork of the filamentous
protein spectrin
red blood cell
160
characteristic of rbc that results from
interactions of its plasma membrane
proteins with an underlying
cytoskeleton
biconcave shape
161
- long, thin, flexible rod
- it maintains the structural integrity and
shape of the plasma membrane
spectrin
162
deformable, netlike meshwork that
covers the entire cytosolic surface of
the red cell membrane
riveted spectrin cytoskeleton to the membrane through various membrane proteins.
163
genetic abnormalities in spectrin
anemic and have red cells that are spherical and fragile
164
- restricts diffusion
- can form mechanical barriers that obstruct the free diffusion of proteins in
the membrane.
cortical cytoskeletal network
165
cortical cytoskeletal network can form ____ ____
mechanical barriers
166
is controlled dynamically
Membrane shape
167
Membrane shape is controlled dynamically because these 3 cell processes require elaborate transient membrane deformations.
vesicle budding, cell movement, and
cell division
168
membrane shape is influenced by?
dynamic pushing and pulling forces exerted by
cytoskeletal or extracellular structures
169
