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

CH 12 Lipids and Cell Membranes P2 Flashcards

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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
Fluorescence Recovery After Photobleaching (FRAP)
allows measurement of lateral mobility of membrane components
26
FRAP Technique
membrane component attached to fluorescent molecule. dye subsequently destroyed by high-intensity light on very small portion of membrane. aka - bleached.
27
S = (4Dt)^1/2
``` 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). ```
28
Lateral Diffusion of Proteins
depends on whether attached to other cellular extracellular components.
29
Fluid Mosaic Model
describes membranes as 2D soln's of oriented lipids and globular proteins
30
The Fluid Mosaic Models allows ____ but not ___.
lateral movement | not rotation through membrane
31
Lipids serve as what things?
solvent | permeability barrier
32
Lipids diffuse how in membranes?
laterally (rapid)
33
Transverse diffusion (flip-flopping) of lipids is rare w/o
enzyme assistance | very slow w/o
34
Prohibiting transverse diffusion of lipids accounts for?
stability of membrane asymmetry.
35
Membrane fluidity is controlled by?
FA composition | cholesterol content
36
Membrane processes depend on
fluidity of membrane
37
Melting Temperature (Tm)
temp at which membrane transitions from highly ordered to very fluid
38
Tm is dependent on
FA length in membrane lipid | degree of cis unsaturation
39
Cholesterol helps maintain ____ in animals.
proper membrane fluidity
40
Phase-Transition
Tm - Melting for phospholipid membrane | packed ordered to random
41
Highly ordered packing of FA chains in a membrane is disrupted by?
cis db's
42
Cholesterol disrupts ____ in FA chains.
tight packing
43
Lipid Rafts
highly dynamic complexes formed btw cholesterol and specific lipids conc. in small regions of membrane.
44
Cholesterol can form complexes w/?
sphingolipids glycolipids some GPI-anchored proteins
45
Lipid Rafts help
``` moderate membrane fluidity function in signal transduction ```
46
Outer and Inner Leaflets (faces) of all biological membranes have diff?
components | enzymatic activities from e/o.
47
All biological membranes are?
asymmetric
48
Na+ - K+ Pump
transports Na+ out and K+ in by hydrolyzing ATP on intracellular side of membrane
49
Eukaryotic cells contain _____ bounds by _____.
compartments | internal membranes
50
Bacterial Membranes
Gram Positive | Gram Negative
51
Gram Positive
bacteria, archaea. | single membrane surrounded by thick cell wall
52
Gram Negative
bacteria. 2 membranes. cell wall (proteins / peptides / carbs) lie btw them. Space btw 2 membranes - periplasm.
53
Gram-Staining of Gram-Positive Bacteria
retain violet stain in thick cell walls
54
Gram-Staining of Gram-Negative Bacteria
doesn't retain stain well bc of thin cell walls
55
Plasma Membrane
single membrane / cell membrane of eukaryotic cells (besides plants)
56
_____ have membranes inside the cell that allow compartmentalization of function.
eukaryotic cells
57
Nuclear Envelope
double membrane connected to another membrane (ER) of eukaryotes
58
ETC takes place in the?
inner membrane of mitochondria
59
Membranes can fuse and separate so that cells and compartments can?
take up, transport, and release molecules
60
Receptor-Mediated Endocytosis
how cells acquire molecules from environment
61
Clathrin
protein | helps internalize receptors bound to cargo
62
Fusion of internal membranes allows the release of?
molecules like NT's from the cell
63
Receptor-Mediated Endocytosis Transferrin
internalization of Fe-bound transferrin associated w/ transferrin receptor (TfR)
64
SNARE Proteins
facilitate membrane fusion by forming tightly coiled 4-helical bundles
65
Vesicle Formation by Receptor-Mediated Endocytosis
receptor binds on cell surface. induces membrane invagination w/ assistance of specialized intracellular proteins (ex clathrin) vesicle formed w/i cell.
66
NT Release
NT-containing synaptic vesicles arrayed near plasma membrane of nerve cell. fuse w/ plasma membrane. release NT into synaptic cleft.
67
Transferrin-Receptor Cycle
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
SNARE Proteins that bring the membranes close together to initiate fusion event?
syntaxin-1 | SNAP25
69
Cardiolipin or phosphatidylglycerol
unusual structure compared to other phosphoglycerides net charge of -2 inverted cone shape
70
Cardiolipin is often found in?
membranes of bacteria archaea | inner membranes of mitochondria
71
In mitochondria Cardiolipin is involved in?
structure / function of respirasome
72
Respirasome
essential in ATP synthesis
73
Proper synthesis and maintenance of Cardiolipin levels requires the enzyme
tafazzin
74
Tafazzin
catalyzes transfer of linoleate chains from phosphatidylcholine to immature cardiolipin.
75
Barth Syndrome
results from mutations that reduce catalytic activity in tafazzin
76
Barth Syndrome Symptoms
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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