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Biochemistry 304 > CH 12 Lipids and Cell Membranes P2 > Flashcards

CH 12 Lipids and Cell Membranes P2 Flashcards

1
Q

Schwann Cell

A

relatively low protein content

lipid-rich plasma membrane

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2
Q

The lipid rich plasma membrane of Schwann Cells serve as?

A

insulator

allow rapid transmission of nerve impulses

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3
Q

Myelination

A

when a Schwann Cell wraps around an axon

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4
Q

Multiple Sclerosis

A

demyelination disease.
impairs myelin assembly.
damages existing myelin.

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5
Q

Myelin

A

lipid-rich plasma membrane of Schwann Cell in peripheral nerves / oligodendrocyte in brain wrapped many times around axon / portion of neuron conducting electrical impulses.

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6
Q

Integral Membrane Proteins (IMPs)

A

embedded in hydrocarbon core of membrane
most traverse lipid bilayer
some composed of beta strands

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7
Q

Peripheral Membrane Proteins (PMPs)

A

bound to polar head groups of membrane lipids / exposed surfaces of IMPs

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8
Q

Membrane-Spanning Alpha Helices

A

common structural feature of IMPs

most common structural motif in membrane proteins

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9
Q

Bacteriorhodopsin

A 
membrane-spanning alpha helix
light-powered proton pump
IMP: 7 membrane-spanning helices.
predominantly hydrophobic
polar charged residues found in cytoplasmic / extracellular regions
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10
Q

Beta Strand IMPs

A

form a pore in the membrane

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11
Q

Porin

A

beta strand-rich IMP.
outside interacts w/ hydrophobic interior of membrane - composed of hydrophobic AAs.
Inside - polar, filled w/ water.
hydrophobic and hydrophilic AAs in adj. positions.

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12
Q

The part of the protein embedded in the membrane can link?

A

protein to membrane surface

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13
Q

Prostaglandin H2 Synthase 1

A

only portion of enzyme embedded in membrane

catalyzes formation of prostaglandin H2 from arachidonic acid in 2 steps.

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14
Q

Cyclooxygenase (COX) activity of prostaglandin H2 synthase-1 is dependent on?

A

the channel connecting active site to membrane interior

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15
Q

Aspirin

A

inhibits cyclooxygenase activity, obstructs channel

transfers acetyl group to serine residue in prostaglandin H2 synthase-1

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16
Q

Hydrophilic Proteins

A

associate w/ membrane by attaching one of a variety of possible hydrophobic groups

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17
Q

Membrane Anchors

A

hydrophobic groups
covalently attached to proteins
tether to proteins in membrane

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18
Q

Transmembrane Helices: Alpha Helix

A

20 residues

can transverse bilayer

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19
Q

Hydrophobicity of AA can by quantified via:

A

determining free E req’d to transfer AA from hydrophobic to hydrophilic environment.

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20
Q

Window

A

examines protein seq by measuring free E by transferring 20 AA’s from hydrophobic to hydrophilic environment

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21
Q

Hydropathy Plot

A

free E plotted against 1st AA of the window
can ID potential membrane-spanning helices when seq’d
doesn’t req additional info for protein

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22
Q

Criterion Level of Hydropathy Plot

A

peaks > 84 kJ/mol-1 indicative of potential transmembrane helices

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23
Q

Glycophorin

A

5’ inside

3’ inside

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24
Q

Porin on the Hydropathy Plot

A

no strong peaks bc constructed from beta strands rather than alpha helices

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25
Q

Fluorescence Recovery After Photobleaching (FRAP)

A

allows measurement of lateral mobility of membrane components

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26
Q

FRAP Technique

A

membrane component attached to fluorescent molecule.
dye subsequently destroyed by high-intensity light on very small portion of membrane.
aka - bleached.

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27
Q

S = (4Dt)^1/2

A 
mobility of fluorescently labeled component
function of how rapidly bleached area recovers fluorescence.
ave distance travelled (S) in time (t) depends on diffusion constant (D).
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28
Q

Lateral Diffusion of Proteins

A

depends on whether attached to other cellular extracellular components.

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29
Q

Fluid Mosaic Model

A

describes membranes as 2D soln’s of oriented lipids and globular proteins

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30
Q

The Fluid Mosaic Models allows ____ but not ___.

A

lateral movement

not rotation through membrane

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31
Q

Lipids serve as what things?

A

solvent

permeability barrier

32
Q

Lipids diffuse how in membranes?

A

laterally (rapid)

33
Q

Transverse diffusion (flip-flopping) of lipids is rare w/o

A

enzyme assistance

very slow w/o

34
Q

Prohibiting transverse diffusion of lipids accounts for?

A

stability of membrane asymmetry.

35
Q

Membrane fluidity is controlled by?

A

FA composition

cholesterol content

36
Q

Membrane processes depend on

A

fluidity of membrane

37
Q

Melting Temperature (Tm)

A

temp at which membrane transitions from highly ordered to very fluid

38
Q

Tm is dependent on

A

FA length in membrane lipid

degree of cis unsaturation

39
Q

Cholesterol helps maintain ____ in animals.

A

proper membrane fluidity

40
Q

Phase-Transition

A

Tm - Melting for phospholipid membrane

packed ordered to random

41
Q

Highly ordered packing of FA chains in a membrane is disrupted by?

A

cis db’s

42
Q

Cholesterol disrupts ____ in FA chains.

A

tight packing

43
Q

Lipid Rafts

A

highly dynamic complexes
formed btw cholesterol and specific lipids
conc. in small regions of membrane.

44
Q

Cholesterol can form complexes w/?

A

sphingolipids
glycolipids
some GPI-anchored proteins

45
Q

Lipid Rafts help

A 
moderate membrane fluidity
function in signal transduction
46
Q

Outer and Inner Leaflets (faces) of all biological membranes have diff?

A

components

enzymatic activities from e/o.

47
Q

All biological membranes are?

A

asymmetric

48
Q

Na+ - K+ Pump

A

transports Na+ out and K+ in by hydrolyzing ATP on intracellular side of membrane

49
Q

Eukaryotic cells contain _____ bounds by _____.

A

compartments

internal membranes

50
Q

Bacterial Membranes

A

Gram Positive

Gram Negative

51
Q

Gram Positive

A

bacteria, archaea.

single membrane surrounded by thick cell wall

52
Q

Gram Negative

A

bacteria.
2 membranes.
cell wall (proteins / peptides / carbs) lie btw them.
Space btw 2 membranes - periplasm.

53
Q

Gram-Staining of Gram-Positive Bacteria

A

retain violet stain in thick cell walls

54
Q

Gram-Staining of Gram-Negative Bacteria

A

doesn’t retain stain well bc of thin cell walls

55
Q

Plasma Membrane

A

single membrane / cell membrane of eukaryotic cells (besides plants)

56
Q

_____ have membranes inside the cell that allow compartmentalization of function.

A

eukaryotic cells

57
Q

Nuclear Envelope

A

double membrane connected to another membrane (ER) of eukaryotes

58
Q

ETC takes place in the?

A

inner membrane of mitochondria

59
Q

Membranes can fuse and separate so that cells and compartments can?

A

take up, transport, and release molecules

60
Q

Receptor-Mediated Endocytosis

A

how cells acquire molecules from environment

61
Q

Clathrin

A

protein

helps internalize receptors bound to cargo

62
Q

Fusion of internal membranes allows the release of?

A

molecules like NT’s from the cell

63
Q

Receptor-Mediated Endocytosis Transferrin

A

internalization of Fe-bound transferrin associated w/ transferrin receptor (TfR)

64
Q

SNARE Proteins

A

facilitate membrane fusion by forming tightly coiled 4-helical bundles

65
Q

Vesicle Formation by Receptor-Mediated Endocytosis

A

receptor binds on cell surface.
induces membrane invagination w/ assistance of specialized intracellular proteins (ex clathrin)
vesicle formed w/i cell.

66
Q

NT Release

A

NT-containing synaptic vesicles arrayed near plasma membrane of nerve cell.
fuse w/ plasma membrane.
release NT into synaptic cleft.

67
Q

Transferrin-Receptor Cycle

A

Fe-bound transferrin binds to TfR on cell surface.
Receptor-mediated endocytosis.
vesicle formation - endosome.
lumen of endosome acidified via H+ pumps.
Fe released from transferrin.
Fe through membrane channels, utilized by cell.
Complex repeats another cycle.

68
Q

SNARE Proteins that bring the membranes close together to initiate fusion event?

A

syntaxin-1

SNAP25

69
Q

Cardiolipin or phosphatidylglycerol

A

unusual structure compared to other phosphoglycerides
net charge of -2
inverted cone shape

70
Q

Cardiolipin is often found in?

A

membranes of bacteria archaea

inner membranes of mitochondria

71
Q

In mitochondria Cardiolipin is involved in?

A

structure / function of respirasome

72
Q

Respirasome

A

essential in ATP synthesis

73
Q

Proper synthesis and maintenance of Cardiolipin levels requires the enzyme

A

tafazzin

74
Q

Tafazzin

A

catalyzes transfer of linoleate chains from phosphatidylcholine to immature cardiolipin.

75
Q

Barth Syndrome

A

results from mutations that reduce catalytic activity in tafazzin

76
Q

Barth Syndrome Symptoms

A

heart chamber dilation
exercise intolerance
impaired growth
malformed mitochondria w/ distorted inner membranes
poorly functioning respirasomes (improper assembly of protein complexes)

Biochemistry 304 (14 decks)

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