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BIO107 - CELL AND MOLECULAR BIOLOGY > Module 2A - Membrane structure > Flashcards

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

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2
Q

What does the plasma membrane maintains?

A
  • characteristics differences between the contents of each organelle and the cytosol.
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3
Q

Characteristics differences between the contents of each organelle and cytosol

A

-ion gradients
-protein sensors or receptors
-lipid bilayer
-membrane proteins

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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

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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

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6
Q

provides the basic structure for all cell membranes

A

lipid bilayer

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7
Q

50% of the mass of the most
animal cell membranes

A

lipids

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8
Q

Lipids are ___% of the mass of most animal cell membranes

A

50%

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9
Q

lipid molecules are
____

A

amphiphilic

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10
Q

What is it called when a lipid contains a hydrophobic tail and hydrophilic heads?

A

Amphiphilic

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11
Q
  • are the most abundant membrane lipids
A

phospholipids

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12
Q

Parts of typical phospholipid molecule

A

have a polar head group (hydrophilic head) and two hydrophobic hydrocarbon tails

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13
Q

Has phosphate group

A

Head

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14
Q

composition of hydrophobic tails

A

two hydrophobic hydrocarbon tails

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15
Q

creates kink in the tail

A

cis-double bonds (unsaturated)

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16
Q

Major lipids in the cell membranes

A

-phosphooglycerides
-sphingolipids
-sphingomyelin
-glycolipids
-cholesterol

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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

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18
Q

Examples of phosphoglycerides

A

-phosphatidylethanolamine
-phosphatidylserine
-phosphatidylcholine

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19
Q

from sphingosine (long acyl acyl chain with an amino group (NH2) and two hydroxyl groups (OH)

A

Sphingolipids

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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

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21
Q

resemble sphingolipids; sugars

A

glycolipids

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22
Q

sterol; contains a rigid ring structure, to which attached a single polar hydroxyl group and a short nonpolar hydrocarbon chain

A

cholesterol

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23
Q

The _____ and _________ nature of the phospholipd molecules cause them to form bilayers spontaneously in aqueous environments.

A

nature, amphiphilic

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24
Q

spontaneously aggregate to bury their hydrophobic tails in the interior

A

amphiphilic molecules

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25
Q

soft nanoparticles with a core-shell structure that are formed when amphiphilic molecules or surfactants aggregate in an aqueous solution

A

spherical micelles

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26
Q

hydrophobic tails sandwiched

A

bilayers

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27
Q

_____________ in the bilayer creates a free edge with water.

A

small tear

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28
Q

the lipids tend to rearrange spontaneously to eliminate the free edge.

A

energetically unfavorable

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29
Q

sealed compartment formed by phospholipid bilayer

A

energetically favorable

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30
Q

able to refuse freely within the plane of a lipid bilayer

A

lipid molecules

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31
Q

construct a lipid molecule with a _____________ or small gold particleattached to its polar group and follow the diffusion of molecules

A

flourescent dye

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32
Q

Lipid bilayer modify a lipid head group to carry a ___________ (=N-O)

A

spin label

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33
Q

Lipid bilayer contains an unpaired electron whose spin creates a paramagnetic signal that can be detected by ________________ spectrum.

A

electron spin resonance (ESR)

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34
Q

phospholipid molecules in synthetic bilayers very rarely migrate from the monolayer on one side to that on the other

A

flip-flop

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35
Q

lipid molecules rapidly exchange places with their neighbors within a monolayer

A

rapid lateral diffusion

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36
Q

individual lipid molecules rotate very rapidly about their long axis and have ________ hydrocarbon chains

A

flexible

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37
Q

the lipid component of a biological membrane is a _____________ in which the constituent molecules are free to move laterally

A

two-dimensional liquid

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38
Q

catalyzes the rapid flip-flop of phospholipids from one monolayer to the other

A

phospholipid translocators (flippases)

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39
Q

a change from a liquid state to a two-dimensional rigid crystalline state at a characteristic temperature

A

phase transition

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40
Q

modulates the properties of lipid bilayers

A

cholesterol

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41
Q

makes lipid bilayer less deformable; decreases the permeability of the bilayer to small water-molecule

A

decrease mobility of the first few CH2 groups

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42
Q

cholesterol prevents the hydrocarbon chains from ____________ and ____________.

A

coming together and crystallizing

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43
Q

20-25-carbon-long prenyl chains

A

archaea

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44
Q

lipid bilayers can be built from molecules with similar features but different ______________.

A

molecular designs

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45
Q

plasma membranes of most eukaruotic cells are _____________ than those of prokaryotes and archaea.

A

more varied

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46
Q

there are how many lipid species?

A

500-2000

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47
Q

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

A

lipid rafts

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48
Q

In which specific lipids come together in separate domains

A

phase segregation

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49
Q

storage of lipids

A

lipid droplets

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50
Q

specialized for lipid storage
-contain a giant liquid droplet

A

fat cells or adipocytes

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51
Q

neutral lipids; exclusively hydrophobic molecules and therefore aggregate into 3-dimensional droplets

A

triacylglycerols and cholesterol esters

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52
Q

contains a large variety of proteins

A

single monolayer or phospholipids

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53
Q

forms rapidly when cells are exposed to high conc. of fatty acids

A

Liquid droplets

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54
Q

two monolayers have different composition

A

Lipid Asymmetry

55
Q

outer monolayer (phosphatidylcholine & sphingomyelin); inner monolayer (phosphatidylethanolamine & phosphatidylserine)

56
Q

outer monolayer

A

phosphatidylcholine and sphingomyelin

57
Q

inner monolayer

A

phosphatidylethanolamine and phosphatidylserine

58
Q

Lipid Asymmetry is important in converting extracellular signals into ___________.

A

intracellular one

59
Q

where does many cytosolic proteins bind that is found in the cytosolic monolayer of the lipid bilayer?

A

specific lipid head groups

60
Q

what id PKC

A

Protein kinase C

61
Q

lipid head groups are modified to create _____________

A

protein-binding sites

62
Q

phospholipids in the cytosolic monolayer

A

phosphatidylinositol (PI)

63
Q

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

A

phospholipases C

64
Q

animals exploit the phospholipid asymmetry of their plasma membrane to distinguish between ______ and ______ cells.

A

live and dead

65
Q

phosphatidylserine translocate from the inner monolayer to the outer monolayer when cells undergo __________.

66
Q

-sugar-containing molecules
-most extreme asymmetry in their membrane distribution.
-found exclusively in the outer monolayer of the lipid membrane

A

glycolipids

67
Q

results from the addition of sugar groups to the lipid molecules in the lumen of the Golgi apparatus

A

asymmetric distribution of glycolipids in the bilayer

68
Q

glycolipids occurrence in all eukaruotic plasma membrane

69
Q

Glycolipids are also found in where?

A

intracellular membrane

70
Q

function of glycolipids come from their _____________.

A

localization

71
Q
  • confined to the exposed apical surface
  • may help to protect the membrane against the harsh
    conditions frequently found there
A

Glycolipids in the Plasma membrane of epithelial cells

72
Q

Harsh conditions typically found in plasma membrane

A

Low pH and high concentrations of degradative enzymes

73
Q

membrane-bound carbohydrate-binding proteins

74
Q

membrane-bound carbohydrate-binding proteins (lectins) bind to the sugar groups on both glycolipids and glycoproteins in the process of cell–cell
adhesion

A

Glycolipids in cell recognition process

75
Q

charged glycolipids; important because of their electric effects

A

Gangliosides

76
Q

Provide entry points for certain bacterial toxins and viruses.

A

Some glycolipids

77
Q

acts as a cell-surface receptor for the bacterial toxin that causes the debilitating diarrhea of cholera

A

ganglioside

78
Q

perform most of the membrane’s specific tasks and
therefore give each type of cell membrane its characteristic functional properties.

A

Membrane proteins

79
Q

The amounts and types of protein in a membrane are

A

Highly variable

80
Q

Membrane proteins can be associated with the lipid bilayer in Various ways

A
  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
Q

Membrane proteins extend
through the lipid bilayer

A

Transmembrane proteins

82
Q

Membrane proteins are ____ having hydrophobic and hydrophilic regions

A

Amphiphilic

83
Q

do not extend into the hydrophobic interior of the lipid bilayer; bound to either face of the membrane by noncovalent interactions (7-8)

A

Peripheral proteins

84
Q

Control the membrane localization of some signaling proteins

A

Lipid Anchors

85
Q

How a _____ is associated with the lipid bilayer reflects the function of the protein

A

Membrane proteins

86
Q

Only ________ can function on both sides of the Bilayer or Transport molecules across it.

A

transmembrane proteins

87
Q

often associated exclusively with either the lipid monolayer or a protein domain on that side.

A

Proteins that function on only one side of the lipid bilayer

88
Q

In most Transmembrane Proteins, the Polypeptide chain crosses the lipid bilayer in an

A

a-helical conformation

89
Q

Characteristics of Transmembrane proteins

A

• 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
Q

are used to localize potential α – helical membrane spanning segments in a polypeptide chain

A

hydropathy plots

91
Q

it is estimated that about 30% of an organism’s proteins are

A

transmembrane proteins

92
Q

Many proteins are

A

Gycosylated

93
Q

are always present on the noncytosolic side of the membrane

A

oligosaccharide chains

94
Q

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

A

disulfide bonds

95
Q

extensively coat the surface of all eukaryotic cells

A

carbohydrates

96
Q

Can Be Solubilized and Purified in Detergents

A

Membrane proteins

97
Q

only agents that disrupt __________ and destroy the _________ can solubilize membrane proteins

A

hydrophobic associations, lipid bilayer

98
Q

small amphiphilic molecules; more soluble in water than lipids

A

detergents

99
Q

polar side

A

ionic or nonionic

100
Q

Ionic

A

sodium dodecyl

101
Q

Nonionic

A

Octylglucoside
and Triton

102
Q

surfactant concentration at which micelle formation is first seen in the solution

A

critical micelle concentration
(CMC)

103
Q

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.

A

When mixed with membranes

104
Q

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

105
Q

can be analyzed by single particle electron microscopy techniques to determine their structure

106
Q

Membrane proteins often function as

A

Large complexes

107
Q

• function as part of multicomponent complexes
• photosynthetic reaction center
• function to capture light energy and use it to pump H+ across the membrane

A

Membrane Proteins Often Function as Large Complexes

108
Q

Many Membrane Proteins Diffuse in the _____

A

Plane of the Membrane

109
Q

membrane proteins do not __________ across the lipid bilayer

A

tumble
(flip-flip)

110
Q

they do rotate about an axis ________ to the plant of the bilayer

A

perpendicular

111
Q

able to move __________ within the membrane

A

laterally,

112
Q

able to move laterally within the
membrane

A

Lateral diffusion

113
Q

some plasma membrane proteins are mobile in the _______

A

plane of the membrane

114
Q

measures lateral diffusion rates of membrane proteins

A

fluorescence recovery after photobleaching (FRAP)

115
Q

FRAP involves marking the membrane
protein of interest with a ______

A

specific fluorescent group (GFP)

116
Q

labeling individual membrane molecules and track their movement by video microscopy

A

single-particle tracking

117
Q

Cells Can Confine Proteins and Lipids to Specific Domains Within
a

118
Q

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

A

Epithelial Cells

119
Q

often essential for the function of the epithelium

A

Asymmetric distribution of membrane proteins in Epithelial cells

120
Q

The barriers set up by a specific type of intercellular junction

A

Tight junction

121
Q

maintain the separation of both protein and lipid molecules

A

Tight junction

122
Q

Create nanoscale raft domains that function in signaling and membrane trafficking

A

protein-protein interactions in membranes

123
Q

More example of nanoscale raft domains that function in signaling and membrane trafficking

A

mammalian spermatozoon

124
Q

a single cell that consists of several structurally and functional distinct parts covered by a continuous plasma membrane

A

Mammalian spermatozoon

125
Q

Gives Membranes Mechanical Strength
and Restricts Membrane Protein Diffusion

A

Cortical Cytoskeleton

126
Q

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

A

biconcave shape

127
Q

long, thin, flexible rod; it maintains the structural integrity and shape of the plasma membrane

128
Q

enables the red cell to withstand the stress on its membrane as it is forced through narrow capillaries

A

spectrin-based cytoskeleton

129
Q

are anemic and have red cells that are spherical and fragile

A

genetic abnormalities in spectrin

130
Q
  • 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
A

Cortical Cytoskeleton

131
Q

Deform bilayers

A

Membrane-bending proteins

132
Q

Shape is controlled dynamically

A

vesicle budding, cell movement, and cell division

133
Q

Shape is influenced by dynamic pushing and pulling forces exerted by ________ or ______

A

cytoskeletal, extracellular structures

BIO107 - CELL AND MOLECULAR BIOLOGY (16 decks)

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