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Biochemistry > Membrane structure and function > Flashcards

Membrane structure and function Flashcards

1
Q

What is the basic structure of phospholipids?

A

glycerol backbone
polar, charged head
nonpolar, fatty acid tail

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2
Q

What are the sites of side chain attachment on glycerol?

A

3 OH groups

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3
Q

Which part of a phospholipid faces the outer side (extracellular/cytoplasm)?

A

polar phosphate head (hydrophilic)

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4
Q

Which part of a phospholipid faces the inner side (lipid bilayer) ?

A

nonpolar fatty acid tail (hydrophobic)

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5
Q

What causes the kinks in phospholipid fatty acid tails?

A

double bonds

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6
Q

Are kinks in fatty acid tails saturated or unsaturated?

A

unsaturated

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7
Q

What effect do to kinks have on the phospholipids?

A

spaces them out so they don’t pack as tight which means that the bilayer is more open

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8
Q

What is the benefit of having mixed saturated and unsaturated fatty acids?

A

faster diffusion

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9
Q

Example of purpose of unsaturated FA in bilayer in real life?

A

drug delivery

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10
Q

What type of phospholipid has O-linked to a charged group and amide-linked to an acyl group, such as a fatty acid?

A

Sphingosine backbone

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11
Q

What type of barrier is a membrane phospholipid bilayer?

A

semipermeable

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12
Q

Can charged molecules diffuse through lipid bilayer?

A

NO

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13
Q

Which molecules can diffuse rapidly across the bilayer?

A

O2
N2
H2O
CO2

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14
Q

Can glycine and other AA such as pyruvate diffuseacorss membranes?

A

NO

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15
Q

Can hydrophobic compounds such as estrogen (hormones) diffuse across membranes?

A

yes

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16
Q

Are lipid components of plasma membrane distributed symmetrically or asymmetrically?

A

asymmetrically

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17
Q

Which component of the PM is distributed symmetrically?

A

cholesterol

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18
Q

What happens when phospholipids are dispersed in water?

A

form vesicles (multilammellar or unilammellar)

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19
Q

Artificially prepared vesicle composed of a lipid bilayer

A

liposome

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20
Q

What can be used to administer and transport nutrients and pharmaceutical drugs in the body?

A

liposome

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21
Q

The pfizer and moderna vaccines use what for drug delivery?

A

liposome

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22
Q

Proteins have numerous localizations in membranes. Name the 7/8 of them.

A
  1. single alpha-helix transmembrane protein
  2. multiple alpha-helices transmembrane protein
  3. rolled up beta sheet (alpha beta barrel)
  4. alpha-helix cytoplasmic partitioned protein
  5. cytoplasmic face protein anchored by a lipid chain in the cytoplasmic monolayer
  6. anchored by oligosaccharide linker to a phosphotidyl inositol in non-cytoplasmic monolayer
    7/8. proteins with main portion on one side of layer anchored by transmembrane spanning alpha-helix
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23
Q

What is the most common structural feature of transmembrane regions of integral membrane proteins?

A

alpha-helix

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24
Q

What are the functions of membrane proteins? (4)

A
  1. cell-cell contact (cell adhesion)
  2. receptor signaling systems
  3. pores and channels (transport)
  4. enzymes
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25
Q

Absorption and synthesis of this is important and much is known about hereditary problems.
Component of PM

A

cholesterol

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26
Q

Do membrane proteins move or stay in place within the lipid bilayer?

27
Q

What allows movement of lipids in PM? (3)

A

flippase
floppase
scramblase

28
Q

Does flippase go down or against concentration gradient?

A

against (uses ATP)
(outer –> inner)
PS, PE

29
Q

Does floppase go down or against concentration gradient?

A

against (uses ATP)
(inner –> outer)
PC, SL

30
Q

Does scramblase go down or against concentration gradient?

A

down (no ATP needed)

cholesterol

31
Q

Does lipid orientation in bilayers vary or stay the same or vary between organelles?

A

vary

ER vs PM

32
Q

specialized domains predominantly within PMs of cells which organize membrane proteins and glycolipids into groupings

A

lipid rafts

33
Q

functional implications of lipid rafts

A

receptor trafficking, neurotransmission and membrane fluidity

34
Q

How do lipid rafts differ from the PM

A

enriched in cholesterol and sphingolipids

35
Q

Are lipid rafts resistant or receptive to dissociation by detergents?

36
Q

Invaginations of PM that form from lipid rafts

37
Q

What are the 5 methods of characterization of lipid membranes?

A 
ultracentrifugation
density gradient ultracentrifugation
electron microscopy 
fluorescence microscopy 
atomic force microscopy
38
Q

Method of lipid membrane characterization used to separate different membrane bound compartments like mitochondria and nucleus

A

ultracentrifugation

39
Q

Method of lipid membrane characterization used to separate membranes containing lipids from proteins

A

density gradient ultracentrifugation

lipids = lower densities; proteins = higher densities

40
Q

Method of lipid membrane characterization that has greater resolving power than a light microscope and can reveal the structure of smaller objects

A

electron microscopy

41
Q

Method of lipid membrane characterization that uses fluorescence and phosphorescence instead of, or in addition to, reflection and absorption to study properties of organic and inorganic substances

A

fluorescence microscopy

42
Q

Method of lipid membrane characterization with very high-resolution type of scanning probe microscopy

A

atomic force microscopy

43
Q

What do detergents do to membranes?

A

solubilize

44
Q

enveloped virus attaches to the CM of recipient cell via receptors and receptors on the surface of the virus, follow by fusion where the envelope blends with the cell membrane and releases it contents (genome) into the cell

A

membrane fusion

45
Q

What are examples of enveloped viruses containing human pathogens?

A 
DNA viruses (herpes)
RNA viruses (covid)
Retroviruses (HIVZ)
46
Q

Describe membrane fusion within coronavirus

A

spike protein on coronavirus binds to receptors on cell causing membrane fusion

47
Q

Why does washing hands with soapy water work to reduce/prevent infection?

A

detergent breaks down the membranes which doesn’t allow them to bind or dump contents into the cell

48
Q

Do bacterial and eukaryotic membranes both have transmembrane spanning proteins?

49
Q

What is the main component of all membranes?

A

phospholipid bilayer

50
Q

What are the 2 main backbones used to make up the phospholipid family?

A

glycerol backbone

sphingosine backbone

51
Q

Some phospholipids can be cleaved into products that function as important _____ ______ ______.

A

intracellular secondary messengers

52
Q

What are liposomes driven by?

A

thermodynamics

53
Q

How do you get a liposome to target specific cell or tissue?

A

Put targeting molecules on outside of liposome (homing peptides)

54
Q

How do we know that proteins move within the lipid bilayer?

A

FRAP

florescence recovery after photobleaching

55
Q

Which leaflet is PS located on?

56
Q

Which leaflet is PE located on?

57
Q

Which leaflet is PI located on?

58
Q

Which leaflet is PC located on?

59
Q

Which leaflet is SL (sphingomyelin) located on?

60
Q

What is scramblase usually associated with?

A

ER-type membranes or membranes where there is fairly symmetrical distribution

61
Q

What are flippases and floppases usually associated with?

A

PM

to re-establish desired asymmetrical distribution

62
Q

Process where very fine needle is dragged across surface which is attached to arm that deflects as it moves. Allows to view where different proteins are localized.

A

Atomic force microscopy

63
Q

What is the receptor for covid?

Biochemistry (9 decks)

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