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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
Absorption and synthesis of this is important and much is known about hereditary problems. Component of PM
cholesterol
26
Do membrane proteins move or stay in place within the lipid bilayer?
Move | FRAP
27
What allows movement of lipids in PM? (3)
flippase floppase scramblase
28
Does flippase go down or against concentration gradient?
against (uses ATP) (outer --> inner) PS, PE
29
Does floppase go down or against concentration gradient?
against (uses ATP) (inner --> outer) PC, SL
30
Does scramblase go down or against concentration gradient?
down (no ATP needed) | cholesterol
31
Does lipid orientation in bilayers vary or stay the same or vary between organelles?
vary | ER vs PM
32
specialized domains predominantly within PMs of cells which organize membrane proteins and glycolipids into groupings
lipid rafts
33
functional implications of lipid rafts
receptor trafficking, neurotransmission and membrane fluidity
34
How do lipid rafts differ from the PM
enriched in cholesterol and sphingolipids
35
Are lipid rafts resistant or receptive to dissociation by detergents?
resistant
36
Invaginations of PM that form from lipid rafts
caveolae
37
What are the 5 methods of characterization of lipid membranes?
``` ultracentrifugation density gradient ultracentrifugation electron microscopy fluorescence microscopy atomic force microscopy ```
38
Method of lipid membrane characterization used to separate different membrane bound compartments like mitochondria and nucleus
ultracentrifugation
39
Method of lipid membrane characterization used to separate membranes containing lipids from proteins
density gradient ultracentrifugation | lipids = lower densities; proteins = higher densities
40
Method of lipid membrane characterization that has greater resolving power than a light microscope and can reveal the structure of smaller objects
electron microscopy
41
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
fluorescence microscopy
42
Method of lipid membrane characterization with very high-resolution type of scanning probe microscopy
atomic force microscopy
43
What do detergents do to membranes?
solubilize
44
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
membrane fusion
45
What are examples of enveloped viruses containing human pathogens?
``` DNA viruses (herpes) RNA viruses (covid) Retroviruses (HIVZ) ```
46
Describe membrane fusion within coronavirus
spike protein on coronavirus binds to receptors on cell causing membrane fusion
47
Why does washing hands with soapy water work to reduce/prevent infection?
detergent breaks down the membranes which doesn't allow them to bind or dump contents into the cell
48
Do bacterial and eukaryotic membranes both have transmembrane spanning proteins?
yes
49
What is the main component of all membranes?
phospholipid bilayer
50
What are the 2 main backbones used to make up the phospholipid family?
glycerol backbone | sphingosine backbone
51
Some phospholipids can be cleaved into products that function as important _____ ______ ______.
intracellular secondary messengers
52
What are liposomes driven by?
thermodynamics
53
How do you get a liposome to target specific cell or tissue?
Put targeting molecules on outside of liposome (homing peptides)
54
How do we know that proteins move within the lipid bilayer?
FRAP | florescence recovery after photobleaching
55
Which leaflet is PS located on?
inner
56
Which leaflet is PE located on?
inner
57
Which leaflet is PI located on?
inner
58
Which leaflet is PC located on?
outer
59
Which leaflet is SL (sphingomyelin) located on?
outer
60
What is scramblase usually associated with?
ER-type membranes or membranes where there is fairly symmetrical distribution
61
What are flippases and floppases usually associated with?
PM | to re-establish desired asymmetrical distribution
62
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.
Atomic force microscopy
63
What is the receptor for covid?
ACE2

Biochemistry (9 decks)

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