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Cell Signaling > Chapter 7 - Membranes, Lipids, and Enzymes That Modify Them > Flashcards

Chapter 7 - Membranes, Lipids, and Enzymes That Modify Them Flashcards

1
Q

What is the main thing that separates the cytosol from the outside environment?

A

water-impermeable lipid membrane

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2
Q

____ dictates spontaneous organization into self sealing sheets and vesicles.

A

hydrophobicity

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3
Q

What are self sealing sheets and vesicles driven by?

A

high thermodynamic cost

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4
Q

Due to the lipid membrane’s ____ arrangement, the biochemical reactions in which they participate have different properties from the aqueous environment that allows free diffusion in ____ space.

A

2D; 3D

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5
Q

What kind of molecules is the lipid bilayer composed of?

A

amphipathic

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6
Q

What kind of structure is favored for relatively large polar heads and small hydrophobic tails?

A

micelles

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7
Q

When there is a tear in the lipid membrane, which portion becomes exposed to water?

A

hydrophobic portion

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8
Q

What factors does the fluidity of the membrane depend on?

A

1) phospholipid composition
2) nature of the hydrocarbon tails (saturation status)
3) amount of cholesterol (animal cells)

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9
Q

When a phospholipid has a shorter tail, what does it mean?

A
  • less interactions between tails
  • increase in fluidity
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10
Q

When there are more double bonds in a phospholipid tails, what happens?

A

kinks interfere with packing closely which increases fluidity

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11
Q

Some cells change the ____ of membrane lipids to adjust its fluidity as an adaptation measure.

A

composition

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12
Q

What is the most abundant lipid in biological membranes?

A

glycerol phospholipids

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13
Q

What kind of linkage exists in a glycerol phospholipid between the glycerol and the hydrocarbon tails?

A

ester linkage

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14
Q

What is the general length of a hydrocarbon tail?

A

14-20 carbons

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15
Q

What kind of phospholipid is this?

A

phosphatidylethanolamine
PE

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16
Q

What kind of phospholipid is this?

A

phosphatidylserine
PS

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17
Q

What kind of phospholipid is this?

A

phosphatidylcholine
PC

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18
Q

What kind of phospholipid is this?

A

phophatidylinositol
PI

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19
Q

What kind of phospholipid is this?

A

sphingomyelin
(sphingolipid)

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20
Q

** move picture here

This lipid is abundant in the plasma membrane of _________ cells.

A

animal cells

mammalian cells

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21
Q

How would you describe a sterol?

A
  • rigid
  • planar
  • polycyclic compound
  • relatively non-polar
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22
Q

What is the term which relates to cholesterol’s ability to manipulate the fluidity of the lipid bilayer?

A

“temperature buffer”
warm - lots of cholesterol stiffens
cold - protects cell membrane from being too rigid

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23
Q

How many rings does cholesterol consist of?

A

4 fused rings

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24
Q

What structure is this?

A

cholesterol

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25
Q

Which kind of lipid molecules are mainly located in the plasma membrane and have sugar groups as heads?

A

glycolipids

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26
Q

Where do glycolipid molecules acquire their sugar groups from?

A

Golgi lumen

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27
Q

Which kind of lipids give off an “apoptotic” signal in the bilayer?

A

phosphatidylserine
PS

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28
Q

Which kind of lipids are primarily found on the cytosolic leaflet?

A

phosphatidylinositides
PI

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29
Q

Which enzyme catalyzes the transfer of random phospholipids from one monlayer to another?

A

scramblase

in the ER

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30
Q

Which enzyme catalyzes the transfer of specific phospholipids to the cytosolic monolayer?

A

flippase

in the Golgi

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31
Q

What organization state of the lipid bilayer?

  • loose & fluid
  • high lateral mobility
  • hydrocarbons tails
  • cis-double bonds
A

liquid-disordered

unsaturated

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32
Q

Which organization state of the lipid bilayer?

  • dense packing
  • limited lateral mobility
  • hydrocarbon
A

solid gel

saturated

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33
Q

Which organization state of the lipid bilayer?

  • highly ordered
  • realtively fluid
  • hydrocarbon chains
  • cholesterol enriched
A

liquid-ordered (raft)

saturated

enriched in spingolipids

34
Q

What is directly realated to the behavior of proteins embedded, and lipids that act as signaling intermediates (e.g. DAG)?

A

fluidity and the rate of protein diffusion

35
Q

What kind of reaction can make molecular interaction more efficient?

A

membrane association

36
Q

Membrane associations show that two interacting protiens bind the most productively in what orientation?

A

in a certain, precise orientation

37
Q

When two proteins are free in a solution, what is their behavior?

A
  • both can rotate around all three axes
  • only as small fraction of collisions will be properly oriented
38
Q

When two proteins are confired to the membrane by an anchor, what is their behavior?

A
  • allowed to rotate only around one axis
  • increases the probablity of collision via proper orientation
39
Q

Different ____ of the membrane have differnt compositions and physical properties.

A

domains

40
Q

The diffusion rate by ____ and ____ shows that the membrane lipids and proteins in the real biological membranes diffuse significantly slower than in artificial membranes consisting of pure lipids.

A

SMT; FRAP

41
Q

The diffusion rate by SMT and FRAP shows that the membrane lipids and proteins in the real biological membranes diffuse significantly ____ than in artificial membranes consisting of pure lipids.

A

slower

42
Q

Why do membrane components move much slower between adjacent domains?

A
  • high density of membrane proteins causing physical contraints
  • cytoskeletal structures that may corral membrane proteins
  • distinct membrane domains with different fluidity
43
Q

When we say signaling proteins are less transient when they are associated with membranes, what does this mean?

A

they are more likely to run into each other

44
Q

A technique to study movement of proteins (especially membrane proteins)

A

Fluorescence Recovery After Photobleaching
FRAP

45
Q

What is FRAP?

A

Fluorescence Recovery After Photobleaching

46
Q

What does FRAP determine?

A

How fast a photobleached blindspot is able to be repaired by protein recovery.

47
Q

How can we track the movement of proteins?

A

in trajectory of motion (seconds)

48
Q

What can reveal some of the pathways that real proteins follow on the surface of a living cell?

A

single molecule tracking (SMT microscopy)

49
Q

Signaling membrane lipids involves their ____ or ____ modification in response to input stimuli.

A

breakdown; chemical

50
Q

What do phospholipases do?

A

cleave/break down phospholipids

51
Q

How are phospholipases classified?

A

by the position of the bonds the enzymes cleave

52
Q

What does phospholipase A2 (PLA2) do?

A

cleaves the fatty acid chain from the middle position of the glycerol backbone
- lyso-phospholipid
- free fatty acid (archidonic acid)

both are bioactive and are the building block for eicosanoids

53
Q

What does phospholipase C (PLC) do?

A

cleaves the phosphorylate head group from the phospholipid
- DAG
- head group moitey

54
Q

What does phospholipase D (PLD) do?

A

cleaves the unphosphorylated head group
- phosphatidic acid (PA)

PA - acts as a bioactive molecule activating mTOR

55
Q

What structure is this?

A

choline

purple: head group
pink: phosphate

56
Q

What structure is this?

A

phosphocholine

purple: head group
pink: phosphate

57
Q

What structure is this?

A

DAG

58
Q

What structure is this?

A

fatty acid

purple: head group
pink: phosphate

59
Q

What structure is this?

A

lyso-PC

pink: phosphate

purple: head group

60
Q

Which cleavage site is represented by the pink arrow?

phosphatidylcholine

A

phospholipase D
- choline
- PA

61
Q

Which cleavage site is represented by the green arrow?

phosphatidylcholine

A

phospholipase D
- phosphocholine
- DAG

62
Q

Which cleavage site is represented by the blue arrow?

phosphatidylcholine

A

phospholipase A2
- lyso-PC
- fatty acid

63
Q

What are the products of the cleavage of phosphatidylcholine via phospholipase A2 (PLA2)?

A
  • lyso-phosphatidylcholine
  • fatty acid (arachidonic acid)
64
Q

What are the products of the cleavage of phosphatidylcholine via phospholipase C (PLC)?

A
  • phosphocholine
  • DAG
65
Q

What are the products of the cleavage of phosphatidylcholine via phospholipase D (PLD)?

A
  • choline
  • phosphatidic acid (PA)
66
Q

What structure is this?

A

sphingosine

67
Q

What structure is this?

A

A Ceramide

68
Q

What structure is this?

A

A Sphingomyelin
(phosphocholine head group)

69
Q

What structure is this?

A

A Sphingomyelin
(phosphoethanolamine head group)

70
Q

What structure is this?

A

A Cerebroside

71
Q

What structure is this?

A

A Ganglioside

72
Q

Which sphinolipid structure can have either a phosphocholine or a phosphoethanolamine head group?

A

A Sphingomyelin

73
Q

PIP2 undergoes hydrolysis via ____ and produces what two components?

A

PLC (phospholipase C)
- DAG
- IP3

74
Q

Which OH positions on this phosphatidylinositol (PI) are available for phosphorylation?

A

positions 2-6

75
Q

What do kinases and phosphatases do to membrane lipids?

A
  • phosphorylation and dephosphorylation
  • change local concentration of various lipids isoforms
76
Q

How are is the activity of kinases/phosphatases regulated?

A
  • changes in the PTM
  • sub-cellular localization
77
Q

Commonly regulated in signaling to generate a variety of bioactive compounds.

A

phosphoinositides

78
Q

What do DAG kinases do?

A

convert DAG to PA

79
Q

What do sphingosine kinases do?

A

convert sphingosine to sphinogsine-I-phosphate (SIP)

can activate the GCPR

80
Q

What are sphingolipids enriched in?

A

a myelin sheath

81
Q

What does DAG and IP3 play a crutial role in?

A
  • PKC activation
  • ER calcium channels
82
Q
A

Cell Signaling (13 decks)

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