Lipids And Cell Membranes

Front 1

what properties make up a biological cell membrane?

Back 1

closed boundaries (sheet-like structures)

composed of lipids and proteins with varying ranges

lipids have both hydro-phobic and philic moieties

proteins serve many functions (pumps, channels, receptors, enzymes)

everything is held together noncovalently

two sides are assymetrical and 2-D fluid structures

polarized (inside -60mV)

Front 2

how thick is a typical membrane?

Back 2

60 A to 100 A
(6 nm to 10 nm)

Front 3

what is a fatty acid?

Back 3

gives membrane hydrophobic quality

long hydrocarbon chains with varying lengths and degrees of unsaturation with a COO- on the end.

Front 4

C18:0

C18:1

C18:2

C18:3

name these bad boys

Back 4

C18:0 octadecanOIC ACID

C18:1 octadecENOIC ACID

C18:2 octadecaDIENOIC ACID

C18:3 octadecaTRIENOIC ACID

Front 5

Where does the numbering start on a fatty acid?

Back 5

at carboxy terminus

C2 is a
C3 is B
terminal methyl is Omega

Front 6

what does cis^9 tell you naming wise?

Why is Omega 3 fatty acid confusing from a naming and counting standpoint?

Back 6

there is a double bond that is cis between 9 and 10

Omega 3 is confusing because you are counting starting from the Omega (distal) end of the thing and the double bond is then starting at 3 to 4.

Front 7

At pH 7, what form are fatty acids found in?

Back 7

ionized form

palmitate (not palmitic acid)

oleate (not oleic acid)

refer to them as their carboxylate forms

Front 8

C14:0

Back 8

Myristate
n-Tetradecanoate
CH3(CH2)12COO-

Front 9

C16:0

Back 9

Palmitate
n-Hexadecanoate
CH3(CH2)14COO-

Front 10

C18:0

Back 10

Stearate
n-Octadecanoate
CH3(CH2)16COO-

Front 11

C20:0

Back 11

Arachadecaonate
n-Eicosanoate
CH3(CH2)18COO-

Front 12

C16:1

Back 12

Palmitoleate
cis-^9-Hexadecenoate
CH3(CH2)5CH==CH(CH2)7COO-

Front 13

C18:1

Back 13

Oleate
cis-^9-Octadecenoate
CH3(CH2)7CH==CH(CH2)7COO-

Front 14

C18:2

Back 14

Linoleate
cis, cis-^9, ^12- Octadecadienoate
CH3(CH2)4(CH==CHCH2)2(CH)6COO-

Front 15

C18:3

Back 15

Linoleate
all cis -^9, ^12, ^15-Octadecatrienoate
CH3CH2(CH==CHCH2)3(CH2)6COO-

Front 16

C20:4

Back 16

Arachidonate
all cis-^5, ^8, ^11, ^14-Eicosatetraenoate
CH3(CH2)4(CH==CHCH2)4(CH2)2COO-

Front 17

What is the typical biological range of Carbons on a fatty acid?

Back 17

14-24 (usually even #)

16-18 most common

Front 18

What impact does higher degrees of unsaturation have on a fatty acid?

Back 18

lowers the melting point

becomes more fluid

Front 19

what are phospholipids?

Back 19

water insoluable, but soluable in organic solvents.

serve as hydrophobic and hydrophilic interacter for messaging, transducting and fuel

Front 20

describe a phospholipid

Back 20

1 or more fatty acid

platform for fatty acid attachment (glycerol or sphingosine)

phosphate

alcohol on the phosphate

Front 21

What is this?

Back 21

phospholipid

Front 22

Describe phosphatidate

Back 22

simplest phosphoglyceride

3-Carbon glycerol platform with C-1 and C-2 esterified to fatty acid carboxyl groups
C-3 is esterified to a phosphate group

Front 23

What are the 2 fatty acids on a phosphoglyceride typically?

Back 23

C1 is stearate (C18:0)

C2 is arachidonate (C20:0)

Front 24

what are the major phosphoglycerides?

Back 24

derived from phosphatidate

add either
Ser
ethanolamine
choline
glycerol
inositol

with an ester bond to the phosphate and hydroxl of alchohol

Front 25

name these bad boys and memorize their functional groups

Back 25

Ser

ethanolamine

choline (3 methyls on the amine)

glycerol

inositol

Front 26

name these phosphoglycerides

Back 26

Phosphatidylserine (PS)

Phosphatidylcholine (PC)

Phosphatidylethanolamine (PE)

Phosphatidylinositol (PI)

Front 27

Name these structures

Back 27

sphingosine

sphingomyelin

Front 28

where is the fatty acid attached to in sphingomyelin?

Back 28

the amine of C2

Front 29

what is a glycolipid?

Back 29

sugar-containing lipids. Like sphingomyelin it is platformed of off sphingosine.

It is different from sphingomyelin by having a sugar attached to the primary hydroxyl of sphingosine

Front 30

How is this lipid different from sphingomyelin?

Back 30

cerebroside

glycolipid

Front 31

What are gangliosides?

Where are the sugars located with regard to the cell?

Back 31

more complex glycolipids

branched chain of up to 7 sugar residues

sugars of glycolipids are always extracellular

Front 32

Describe cholesterol.

Back 32

steroid with 4 linked hydrocarbon rings.
on one end is a hydrocarbon tail and a hydroxyl group on the other end.

Front 33

What is the orientation of cholesterol in the cell membrane?

Back 33

parallel to phospholipids because the hydroxyl tail interacts with the proximal phospholipid head

Front 34

cholesterol is found in all membranes of every kind of life form. verdad o falso?

Back 34

False. Prokaryotes do not have cholesterol.

Front 35

How are archea membranes unique?

Back 35

non-polar chains attached to glycerol backbone

glycerol stereochemistry is inverted compared to phosphatidate

alkyl chains are branched and saturated

due to ether linkage they are resistant to hydrolysis and due to alkyl chains resistant to oxidation

lipids help archea withstand high temps, high salt, low PH

Front 36

what is this structure and why is it unique?

Back 36

archea lipid

branched, saturated alkyl chains with ether linkage

inverted stereochem of glycerol

Front 37

what is an amphipathic molecule?

Back 37

molecule with both hydrophilic and hydrophobic moieties

circle likes water, green tails hate water

Front 38

what is a micelle?

Back 38

small globular structure <200A (20nm) in diameter

Front 39

what is a lipid bilayer?

Back 39

2 sheets of lipids.

Tails interact with eachother while the heads face out and interact with water.

middle part is now a permeable barrier

can form more extensive dimensions (1mm) over the micelle config. (those fatty acids won't fit in the middle)

Front 40

Give an example of a molecule that readily forms a micelle?

Back 40

sodium palmitate
(only has one single fatty acid chain)

Front 41

describe the forces that make for lipid bilayers forming rapidly and spontaneously.

Back 41

hydrophobic tail forces and van der waals forces between the hydrocarbon tails

hydrophilic forces of water interacting with heads
(electrostatic and H bonding)

Front 42

what does cooperative structure mean?

Back 42

many reinforcing, noncovalent interactions

makes lipid bilayers extensive, compartmentalized and self-sealing

Front 43

what is a liposome?

Back 43

the creation of a lipid vessicle with an aqueous center

important because it allows us to study membrane permeability and to deliver drugs in the aqueous bit

Front 44

how do you form a liposome?

Back 44

put PC in aq medium and sonicate

vessicles are uniform, spherical and about (50nm) in diameter

Front 45

describe molecular trapping.

Back 45

first you make the liposomes with GLY in the vessicle.

Then you can observe how the GLY gets out and determine the lipid bilayers permeability to GLY

You can also insert proteins using a detergent to see how permeability is effected

Front 46

what is doxil?

Back 46

long-acting liposomal version of doxorubicin used to treat a variety of cancers

greater efficacy and lower cardiotoxicity

Front 47

What is Lipoplatin?

Back 47

liposomal cisplatin 110 nm

treat karposi's sarcoma and multiple myeloma

reduced nephrotoxicity, peripheral neuropathy, ototoxicity, myelotoxicity, and less nausea and vomiting

Front 48

How is the permeability of a lipid bilayer different for water and Na or K?

Back 48

lipid bilayers are relatively impermeable to ions and polar molecules

But water, with its small size, abundance and lack of charge goes through easily

Front 49

describe how a small molecule might make "break on through, to the other side"

Back 49

solvates in water, dissolves in hydrocarbon core of membrane, diffuses on through and gets re-solvated on the other side.

So those that easily replace their coordination shell are more quickly permeable

Front 50

Are ions more or less permeable than glucose?

Is Glucose more or less permeable than indole?

Back 50

ions less permeable than glucose

glucose less permeable than indole?

Front 51

Why is Tryptophan less permeable than indole?

Back 51

indole lacks ionic groups--more energetically favorable to pass through the hydrophilic center of membrane

Front 52

describe the relationship between membrane lipids and proteins

Back 52

protiens transport chemicals and info across a membrane

membrane lipids create the appropriate environment for the action of these proteins

Front 53

what is the concentration of proteins for an electrically insulated environment like a nerve cell membrane?

Back 53

18% proteins in myelin and those proteins will be found in the synapses

Front 54

what is the concentration of proteins in a metabollically active membrane?

Back 54

50% proteins in plasma membranes
pumps channels receptors and enzymes

Front 55

What concentration of proteins make up an energy transducing membrane?

Back 55

inner mitochondrial membrane is a whopping 75% proteins.
Not as much lipids but a lot of cardiolipin

Front 56

what are the 3 ways proteins can be associated with membranes?

Back 56

peripherally
integrally
half and half (bottom half of protein has series of a helices that interact with hydrophobic middle of membrane)

Front 57

how are peripheral membrane proteins attached to membrane?

Back 57

electrostatic and H bonded to lipid heads

bind to integral proteins

hydrophobic fatty acid chain attaches to lipid bilayer

Front 58

How are integral proteins anchored in membrane?

Back 58

They interact extensively with the hydrocarbon middle tails

Front 59

What are 2 types of structures for integral membrane proteins?

Back 59

a helices

B strands

Front 60

describe bacteriorhodopsin

Back 60

7 perpendicular a helices span 45 A width of cell membrane

H+ gradient uses light energy to pump H+ out and synthesize ATP

a helics are hydrophobic with non polar residues sticking out

Front 61

what are the most common structural motif in membrane spanning proteins?

Back 61

a-helices

Front 62

what is a porin?

Back 62

channel protein

single antiparallel B-sheet which folds in a way to make a cylindrical channel

The outside surface is nonpolar

The inside surface is hydrophilic and water filled

Front 63

Where are porins commonly found?

Back 63

E. coli

Front 64

How is the compatible structure of a porin created?

Back 64

alternating hydrophobic and hydrophilic residues that are h-bonded diagonally.

Front 65

draw the structure for arachidonate

Back 65

Front 66

what is prostaglandin H2 synthase-1 and what does it do?

Back 66

an enzyme that catalyzes the conversion of arachidonic acid into prostaglandin H2

Initiates COX-1 (cyclooxygenase rxn)
(perioxidase rxn)

Front 67

what does prostaglandin H2 do in the body?

Back 67

promotes inflammation and modulates gastric acid secretion

Front 68

how does prostaglandin H2 differ synthase-1 differ from bacteriorhodopsin?

Back 68

it has a-helices, but they are on the bottom of the protein and their hydrophobic amino acid side chains are what is imbedded in the membrane

Front 69

What is thromboxane A2?

Back 69

prothrombolitic
activation and aggregation of platelets

causes vasoconstriction

BAD

aspirin works for keeping blood thinner by irreversibly inhibiting COX-1 and thus the formation of Prostaglandin H2 and thus TXA2

Front 70

What is PGI2 (prostacyclin)

Back 70

eicosanoid

decreases platelet aggregation

causes vasodilation

GOOD

Front 71

Is prostaglandin H2 synthase 1 an integral or peripheral protein?

Back 71

integral, even though it is not fully imbedded.

Requires organic solvent or detergent to isolate that sucker.

Front 72

which residue inside the COX-1 protein channel gets the inhibiting aspirin acetyl group?

Back 72

Ser 530

Front 73

What are 2 important feature of how proteins interact with membranes?

Back 73

1). parts of protein that interact with hydrophobic part of membrane are coated with non-polar amino acids side chains and parts interacting with aq part are hydrophilic

2). imbedded structures are quite regular participate in H bonding which are difficult to sever

Front 74

name the anchors for

palmitoyl

farnesyl

GPI

Back 74

thioester

C-terminus

C-terminus

Front 75

name the 10 non polar amino acid residues

Back 75

P-lease
M-ail
I-n
L-ove
C-ards
Tr-pping
A
Th-reesome
Girly Gly

Front 76

What is the "window" in hydropathy plot?

Back 76

sequence of 20 residues in which the calculations of free energy will determine whether they are imbedded o or not.

The calculations are plotted against the first amino acid at the start of the window and anything over +20 kcal/mol indicates a likely membrane spanning window.

Front 77

what is glycophorin?

Back 77

an erythrocyte membrane protein that has a predicted membrane spanning region from a hydropathy plot which has been proven experimentally.

Front 78

Are hydrophathy plots always correct?

Back 78

No, even some soluable proteins contain large non-polar regions and some membrane spanning protein segments go undetected by hydropathy plots, like porin.

Front 79

Describe the FRAP process of determining lateral diffusion

Back 79

--cell surface fluoresces with labled surface

--fluorescent area is bleached and destroyed

--fluorescence intensity recovers as diffusion occurs.

--the rate of recover depends on the diffusion coefficient

Front 80

what is the diffusion coefficient of phospholipids?

Back 80

1 Mm2s-1

diffuses ~2Mm / s

(this ~100x that of water--more like olive oil)

Front 81

what is the diffusion coefficient of proteins?

what is a fast protein?

What is a slow protein?

Back 81

a range

fast protein is photoreceptor protein rhodopsin
0.4 Mm2/s

slow protein is peripheral glycoprotein fibronectin
<10-4 Mm2/s

Front 82

Why is fibronectin a slow diffuser?

Back 82

anchored to actin filaments through transmembrane protein integrin (stuck in the extracellular matrix and cytoskeleton)

Front 83

what is the fluid mosaic model?

Back 83

membranes are 2-D solutions of oriented lipids and globular proteins

lipid bilayer is a solvent for integral proteins and a permeability barrier

membrane proteins are free to diffuse laterally in lipid matrix.

Front 84

what is transverse diffusion

Back 84

flip flop.

takes a long time 10 to 9th as long as a lipid laterally diffuses 50 A.

Front 85

Where are PE and PS predominantly located?

Back 85

The aminophospholipids, phosphatidylethanolamine (PE) and in particular phosphatidylserine (PS) are preferentially located in the inner leaflet of the membrane bilayer

Front 86

Where are sphingomyelin and PC predominantly located?

Back 86

the other major components sphingomyelin (SM) and phosphatidylcholine (PC) are more abundant in the outer leaflet

Front 87

what are flippases?

Back 87

translocater which flip flops PE and PS from outer to inner

Front 88

What are floppases?

Back 88

move phospholipids from inner to outer

needs ATP
ABC transporter family

Front 89

What are scramblases?

Back 89

move any phospholipid across bilayer down its concentration gradient

does not need ATP

Front 90

What is membrane fluidity depend upon?

Back 90

The composition of fatty acids and their properties.

rigid fatty acids are saturated and unbent with lots of good H bonding and thus higher melting points

more fluid membranes have unsaturated fatty acids that are bent and thus less H bonds and thus lower melting points.

Front 91

How does fatty acid chain length influence fluidity of membranes?

Back 91

each additional -CH2- adds -0.5 kcal/mol to free energy of interaction between 2 adjacent hydrocarbon chains.

longer chains interact more strongly

Front 92

How does E. coli alter its fatty acid chains when it is trying to grow in colder temps?

Back 92

decreases the ratio of saturated to unsaturated so that there are less rigid (saturated) fatty acids which prevents the membrane from becoming too rigid in this colder environment

Front 93

How do animals regulate membrane fluidity?

Back 93

cholesterol

Front 94

what structurally about cholesterol helps it regulate membrane fluidity?

Back 94

bulky steroid nuclues with a hydroxl group at one end and a flexible hydrocarbon tail at the other.

hydroxyl group interacts with aqueous environment (head group)

hydrocarbon tail is in non-polar core

Front 95

what is a lipid raft?

Back 95

cholesterol forms complexes with certain phospholipids concentrated in certain areas of the membrane.

These guys serve to moderate membrane fluidity. Makes them less fluid but also less likely to experience phase change

Front 96

asymmetric membranes means what?

Back 96

inside and outside have different components and enzymes and thus different activities.

Na+ and K+ ATPase pump

Na+ and ATP inside cell

K+ outside

Front 97

what is ouabain?

Back 97

cardiotonic steroid that inhibits the Na+ and K+ pumps

ONLY works on outside of cell.