Module 2A - Membrane structure Flashcards
1
Q
encloses the cell, defines its boundaries, and maintains the essential differences between the cytosol and the extracellular environment.
A
Plasma membrane
2
Q
What does the plasma membrane maintains?
A
- characteristics differences between the contents of each organelle and the cytosol.
3
Q
Characteristics differences between the contents of each organelle and cytosol
A
-ion gradients
-protein sensors or receptors
-lipid bilayer
-membrane proteins
4
Q
- established by the activities of specialized membrane proteins
- can be used to synthesize ATP, to drive the transmembrane movement of selected solutes, or, in nerve and muscle cells, to produce and transmit electrical signals.
A
ion gradients
5
Q
- the plasma membrane also contains proteins that act as sensors of external signals, allowing the cell to change its behavior in response to environmental cues
- transfer information—rather than ions or molecules—across the membrane.
A
proteins sensors or receptors
6
Q
provides the basic structure for all cell membranes
A
lipid bilayer
7
Q
50% of the mass of the most
animal cell membranes
A
lipids
8
Q
Lipids are ___% of the mass of most animal cell membranes
A
50%
9
Q
lipid molecules are
____
A
amphiphilic
10
Q
What is it called when a lipid contains a hydrophobic tail and hydrophilic heads?
A
Amphiphilic
11
Q
- are the most abundant membrane lipids
A
phospholipids
12
Q
Parts of typical phospholipid molecule
A
have a polar head group (hydrophilic head) and two hydrophobic hydrocarbon tails
13
Q
Has phosphate group
A
Head
14
Q
composition of hydrophobic tails
A
two hydrophobic hydrocarbon tails
15
Q
creates kink in the tail
A
cis-double bonds (unsaturated)
16
Q
Major lipids in the cell membranes
A
-phosphooglycerides
-sphingolipids
-sphingomyelin
-glycolipids
-cholesterol
17
Q
-main phospholipids
-three-carbon glycerol backbone
-3rd carbon is attached to a phosphate group, which is linked to a head group.
A
Phosphoglycerides
18
Q
Examples of phosphoglycerides
A
-phosphatidylethanolamine
-phosphatidylserine
-phosphatidylcholine
19
Q
from sphingosine (long acyl acyl chain with an amino group (NH2) and two hydroxyl groups (OH)
A
Sphingolipids
20
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
21
Q
resemble sphingolipids; sugars
A
glycolipids
22
Q
sterol; contains a rigid ring structure, to which attached a single polar hydroxyl group and a short nonpolar hydrocarbon chain
A
cholesterol
23
Q
The _____ and _________ nature of the phospholipd molecules cause them to form bilayers spontaneously in aqueous environments.
A
nature, amphiphilic
24
Q
spontaneously aggregate to bury their hydrophobic tails in the interior
A
amphiphilic molecules
25
soft nanoparticles with a core-shell structure that are formed when amphiphilic molecules or surfactants aggregate in an aqueous solution
spherical micelles
26
hydrophobic tails sandwiched
bilayers
27
_____________ in the bilayer creates a free edge with water.
small tear
28
the lipids tend to rearrange spontaneously to eliminate the free edge.
energetically unfavorable
29
sealed compartment formed by phospholipid bilayer
energetically favorable
30
able to refuse freely within the plane of a lipid bilayer
lipid molecules
31
construct a lipid molecule with a _____________ or small gold particleattached to its polar group and follow the diffusion of molecules
flourescent dye
32
Lipid bilayer modify a lipid head group to carry a ___________ (=N-O)
spin label
33
Lipid bilayer contains an unpaired electron whose spin creates a paramagnetic signal that can be detected by ________________ spectrum.
electron spin resonance (ESR)
34
phospholipid molecules in synthetic bilayers very rarely migrate from the monolayer on one side to that on the other
flip-flop
35
lipid molecules rapidly exchange places with their neighbors within a monolayer
rapid lateral diffusion
36
individual lipid molecules rotate very rapidly about their long axis and have ________ hydrocarbon chains
flexible
37
the lipid component of a biological membrane is a _____________ in which the constituent molecules are free to move laterally
two-dimensional liquid
38
catalyzes the rapid flip-flop of phospholipids from one monolayer to the other
phospholipid translocators (flippases)
39
a change from a liquid state to a two-dimensional rigid crystalline state at a characteristic temperature
phase transition
40
modulates the properties of lipid bilayers
cholesterol
41
makes lipid bilayer less deformable; decreases the permeability of the bilayer to small water-molecule
decrease mobility of the first few CH2 groups
42
cholesterol prevents the hydrocarbon chains from ____________ and ____________.
coming together and crystallizing
43
20-25-carbon-long prenyl chains
archaea
44
lipid bilayers can be built from molecules with similar features but different ______________.
molecular designs
45
plasma membranes of most eukaruotic cells are _____________ than those of prokaryotes and archaea.
more varied
46
there are how many lipid species?
500-2000
47
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
48
In which specific lipids come together in separate domains
phase segregation
49
storage of lipids
lipid droplets
50
specialized for lipid storage
-contain a giant liquid droplet
fat cells or adipocytes
51
neutral lipids; exclusively hydrophobic molecules and therefore aggregate into 3-dimensional droplets
triacylglycerols and cholesterol esters
52
contains a large variety of proteins
single monolayer or phospholipids
53
forms rapidly when cells are exposed to high conc. of fatty acids
Liquid droplets
54
two monolayers have different composition
Lipid Asymmetry
55
outer monolayer (phosphatidylcholine & sphingomyelin); inner monolayer (phosphatidylethanolamine & phosphatidylserine)
rbc
56
outer monolayer
phosphatidylcholine and sphingomyelin
57
inner monolayer
phosphatidylethanolamine and phosphatidylserine
58
Lipid Asymmetry is important in converting extracellular signals into ___________.
intracellular one
59
where does many cytosolic proteins bind that is found in the cytosolic monolayer of the lipid bilayer?
specific lipid head groups
60
what id PKC
Protein kinase C
61
lipid head groups are modified to create _____________
protein-binding sites
62
phospholipids in the cytosolic monolayer
phosphatidylinositol (PI)
63
cleaves an inositol phospholipid in the cytosolic monolayer of the plasma membrane to generate fragments-one remains in the membrane and helps activate protein kinase C, the other is released into the cytosol and stimulate the release of Ca2+ from the endoplasmic reticulum
phospholipases C
64
animals exploit the phospholipid asymmetry of their plasma membrane to distinguish between ______ and ______ cells.
live and dead
65
phosphatidylserine translocate from the inner monolayer to the outer monolayer when cells undergo __________.
apoptosis
66
-sugar-containing molecules
-most extreme asymmetry in their membrane distribution.
-found exclusively in the outer monolayer of the lipid membrane
glycolipids
67
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
68
glycolipids occurrence in all eukaruotic plasma membrane
5%
69
Glycolipids are also found in where?
intracellular membrane
70
function of glycolipids come from their _____________.
localization
71
- confined to the exposed apical surface
- may help to protect the membrane against the harsh
conditions frequently found there
Glycolipids in the Plasma membrane of epithelial cells
72
Harsh conditions typically found in plasma membrane
Low pH and high concentrations of degradative enzymes
73
membrane-bound carbohydrate-binding proteins
Lectins
74
membrane-bound carbohydrate-binding proteins (lectins) bind to the sugar groups on both glycolipids and glycoproteins in the process of cell–cell
adhesion
Glycolipids in cell recognition process
75
charged glycolipids; important because of their electric effects
Gangliosides
76
Provide entry points for certain bacterial toxins and viruses.
Some glycolipids
77
acts as a cell-surface receptor for the bacterial toxin that causes the debilitating diarrhea of cholera
ganglioside
78
perform most of the membrane’s specific tasks and
therefore give each type of cell membrane its characteristic functional properties.
Membrane proteins
79
The amounts and types of protein in a membrane are
Highly variable
80
Membrane proteins can be associated with the lipid bilayer in Various ways
1. Amphiphilic
2. Transmembrane proteins
3. Located entirely in the cytosol and are attached
to the cytosolic monolayer of the lipid bilayer (4-5)
4. entirely exposed at the external cell surface, by a covalent linkage
(glycosylphosphatidylinositol; GPI) (6)
5. Peripheral membrane proteins
81
Membrane proteins extend
through the lipid bilayer
Transmembrane proteins
82
Membrane proteins are ____ having hydrophobic and hydrophilic regions
Amphiphilic
83
do not extend into the hydrophobic interior of the lipid bilayer; bound to either face of the membrane by noncovalent interactions (7-8)
Peripheral proteins
84
Control the membrane localization of some signaling proteins
Lipid Anchors
85
How a _____ is associated with the lipid bilayer reflects the function of the protein
Membrane proteins
86
Only ________ can function on both sides of the Bilayer or Transport molecules across it.
transmembrane proteins
87
often associated exclusively with either the lipid monolayer or a protein domain on that side.
Proteins that function on only one side of the lipid bilayer
88
In most Transmembrane Proteins, the Polypeptide chain crosses the lipid bilayer in an
a-helical conformation
89
Characteristics of Transmembrane proteins
• unique orientation in the membrane
• different functions of its cytosolic and noncytosolic domains
• membrane-spanning segment of the polypeptide chain, which contact the hydrophobic area of
the lipid bilayer are formed into α helix
• single-pass transmembrane proteins
– polypeptide chain crosses only
once
• multipass transmembranes
• multiple transmembrane strands of a
polypeptide chain to be arranged as
a β sheet that is rolled up into a
cylinder
90
are used to localize potential α – helical membrane spanning segments in a polypeptide chain
hydropathy plots
91
it is estimated that about 30% of an organism’s proteins are
transmembrane proteins
92
Many proteins are
Gycosylated
93
are always present on the noncytosolic side of the membrane
oligosaccharide chains
94
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
95
extensively coat the surface of all eukaryotic cells
carbohydrates
96
Can Be Solubilized and Purified in Detergents
Membrane proteins
97
only agents that disrupt __________ and destroy the _________ can solubilize membrane proteins
hydrophobic associations, lipid bilayer
98
small amphiphilic molecules; more soluble in water than lipids
detergents
99
polar side
ionic or nonionic
100
Ionic
sodium dodecyl
101
Nonionic
Octylglucoside
and Triton
102
surfactant concentration at which micelle formation is first seen in the solution
critical micelle concentration
(CMC)
103
The hydrophobic ends of detergents bind to the hydrophobic regions of the membrane proteins, where they displace lipid molecules with a collar of detergent molecules.
When mixed with membranes
104
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
105
can be analyzed by single particle electron microscopy techniques to determine their structure
Nanodiscs
106
Membrane proteins often function as
Large complexes
107
• function as part of multicomponent complexes
• photosynthetic reaction center
• function to capture light energy and use it to pump H+ across the membrane
Membrane Proteins Often Function as Large Complexes
108
Many Membrane Proteins Diffuse in the _____
Plane of the Membrane
109
membrane proteins do not __________ across the lipid bilayer
tumble
(flip-flip)
110
they do rotate about an axis ________ to the plant of the bilayer
perpendicular
111
able to move __________ within the membrane
laterally,
112
able to move laterally within the
membrane
Lateral diffusion
113
some plasma membrane proteins are mobile in the _______
plane of the membrane
114
measures lateral diffusion rates of membrane proteins
fluorescence recovery after photobleaching (FRAP)
115
FRAP involves marking the membrane
protein of interest with a ______
specific fluorescent group (GFP)
116
labeling individual membrane molecules and track their movement by video microscopy
single-particle tracking
117
Cells Can Confine Proteins and Lipids to Specific Domains Within
a
Membrane
118
In ________ 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
119
often essential for the function of the epithelium
Asymmetric distribution of membrane proteins in Epithelial cells
120
The barriers set up by a specific type of intercellular junction
Tight junction
121
maintain the separation of both protein and lipid molecules
Tight junction
122
Create nanoscale raft domains that function in signaling and membrane trafficking
protein-protein interactions in membranes
123
More example of nanoscale raft domains that function in signaling and membrane trafficking
mammalian spermatozoon
124
a single cell that consists of several structurally and functional distinct parts covered by a continuous plasma membrane
Mammalian spermatozoon
125
Gives Membranes Mechanical Strength
and Restricts Membrane Protein Diffusion
Cortical Cytoskeleton
126
the characteristic ________ of a red blood cell results from interactions of its plasma membrane proteins with an underlying cytoskeleton, which consists mainly of a meshwork of the filamentous protein spectrin
biconcave shape
127
long, thin, flexible rod; it maintains the structural integrity and shape of the plasma membrane
spectrin
128
enables the red cell to withstand the stress on its membrane as it is forced through narrow capillaries
spectrin-based cytoskeleton
129
are anemic and have red cells that are spherical and fragile
genetic abnormalities in spectrin
130
- Restricts diffusion
- Form mechanical barriers that obstruct the free diffusion of proteins in the membrane
- deformable, netlike meshworks that covers the entire cytosolic surface of the red cell membrane
Cortical Cytoskeleton
131
Deform bilayers
Membrane-bending proteins
132
Shape is controlled dynamically
vesicle budding, cell movement, and cell division
133
Shape is influenced by dynamic pushing and pulling forces exerted by ________ or ______
cytoskeletal, extracellular structures
