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Eukaryotic Cell Biology > Chapter 10: Membrane Structure > Flashcards

Chapter 10: Membrane Structure Flashcards

1
Q

Membranes are essential for what?

A

Cell viability

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2
Q

Membranes are used to establish what that have distinct and diverse functions?

A

Compartments

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3
Q

Name three functions of membranes

A
  1. Synthesizing ATP
  2. Transmitting electrical signals
  3. Acting as sensor to extracellular cues
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4
Q

All biological membranes have a common what?

A

General structure

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5
Q

Basic structure of all cellular membranes include what?

A

Lipid molecules and membrane associated proteins

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6
Q

The most abundant membrane lipids are what?

A

Phospholipids

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7
Q

What are phospholipids composed of?

A

A polar (water loving) head group and two hydrophobic (water fearing) hydrocarbon tails

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8
Q

The nonpolar tails of phospholipids vary in their what?

A

Length (13-24 carbons)

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9
Q

One of the hydrocarbon tails of a phospholipid may contain one or more whats which impacts lipid packing within the bilayer?

A

Double bonds

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10
Q

The differences in the length of the tail plus the number of double bonds influence what?

A

The fluidity of the membrane

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11
Q

What are these structures?

A

Phospholipids

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12
Q

What are the main phospholipids?

A

Phosphoglycerides

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13
Q

Phosphoglycerides contain what kind of backbone?

A

A 3 carbon glycerol backbone

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14
Q

In a phosphoglyceride, 2 carbons of the glycerol are linked to what?

A

Fatty acid tails

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15
Q

In a phosphoglyceride, the 3rd carbon is linked to a phosphate group which is linked to a what?

A

Head group

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16
Q

Give an example of a phosphoglyceride

A

Phosphotidylcholine

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17
Q

What is this structure?

A

Lipid Bilayer

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18
Q

Identify structure

A

Phosphatidylethanolamine

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19
Q

What is this structure?

A

Cholesterol

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20
Q

What is A and B?

A

A: Lipid Micelle; B: Lipid Bilayer

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21
Q

What is a rigid ring structure attached to a polar hydroxyl head group and short nonpolar hydrocarbon tail?

A

Cholesterol

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22
Q

What packs in between phospholipids close to the nonpolar head groups?

A

Cholesterol

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23
Q

How many cholesterol molecules are present per phospholipid?

A

One cholesterol molecule present per phospholipid

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24
Q

Cholesterol has an impact on what property of the lipid bilayer?

A

The permeability-barrier properties of the bilayer

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25
Q

Cholesterol makes the bilayer less permeable to what?

A

Small water soluble molecules

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26
Q

Yes or No: Does cholesterol change the fluid properties of the membrane?

A

No

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27
Q

Membrane fluidity is influenced by two factors

A

Composition and temperature

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28
Q

Membranes with short hydrocarbon tails/multiple double bonds are more fluid at lower temperatures than membranes composed of what? Due to differences in what?

A

Long, saturated hydrocarbon tails due to differences in phospholipid packing

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29
Q

Which one has unsaturated hydrocarbon chains with cis-double bonds or saturated hydrocarbon chains?

A

A: unsaturated hydrocarbon chains with cis-double bonds B: saturated hydrocarbon chains

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30
Q

Which are thinner: Membranes composed of unsaturated phospholipids or membranes composed of saturated phospholipids?

A

Unsaturated phospholipids

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31
Q

Where does most of the movement in a layer of phospholipid occur?

A

Within the plane of each monolayer

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32
Q

Lipids rotate on their what?

A

Axis

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33
Q

Lipids exchange positions with neighboring lipids by what?

A

Lateral diffusion

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34
Q

Which motion in the lipid layer occurs most often?

A

A: Lateral diffusion

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35
Q

Which motion in the lipid layer is rare?

A

B: Flip-flop

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36
Q

Lipids molecules in the plasma membrane associate in specialized lipid subdomains referred to as what?

A

Lipid rafts

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37
Q

What regions are enriched with sphingolipids and cholesterol and are involved in organizing membrane proteins?

A

Lipid rafts

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38
Q

Lipid composition of membrane proteins differ how?

A

From organism to organism and organelle to organelle

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39
Q

Cholesterol is absent from what organism?

A

E. coli

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40
Q

What organism’s plasma membrane is composed primarily of phosphotidylethanolamine?

A

E. coli

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41
Q

A typical cell membrane can contain upwards of how many different lipid types that vary in their head groups, hydrocarbon chain length and saturation?

A

1, 000

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42
Q

The two leaflets of a lipid bilayer differ in their what?

A

Composition

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43
Q

What are sugar modified lipids?

A

Glycolipids

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44
Q

What is this structure?

A

Glycolipid

45
Q

What are localized to the outer leaflet of the plasma membrane bilayer?

A

Glycolipids

46
Q

Asymmetry is because sugar addition occurs only within the lumen of the what?

47
Q

Glycolipids make up how much of all plasma membrane lipids?

48
Q

What three things happen after the exposure of sugar molecules to the extracellular environment?

A
  1. It protects the membrane from low pH and degradative enzymes 2. It modulates the electrical properties of the membrane 3. It functions in cell-cell adhesion
49
Q

One difference in the composition of the bilayers was the presence of glycolipids. What is the second difference?

A

The second difference is in the distribution of phospholipid head groups

50
Q

What localizes only to the inner leaflet of a plasma membrane?

A

Phosphotidylserine

51
Q

Phosphotidylserine gives a what kind of charge to the inner leaflet?

A

Negative charge

52
Q

The difference in the composition of each leaflet of the lipid bilayer is extremely important for what?

A

Cell function

53
Q

In addition to cell function, lipid layer asymmetry is used for what other two functions?

A
  1. Propagation of an external signal into an intracellular response 2. Distinction of live versus dead cells
54
Q

Identify the membrane proteins

A
  1. Single-pass alpha helix
  2. Multipass alpha-helix
  3. Beta-sheet (Beta-barrel)
  4. alpha-helix anchor
  5. Fatty acid or prenyl group anchor
  6. Oligosaccharide linker (GPI)
  7. Noncovalent interactions
  8. Noncovalent interactions
55
Q

Number and type of proteins present in a membrane will vary from what to what?

A

Membrane to membrane

56
Q

Membrane proteins vary in their structure and in the way they associate with the what?

A

Lipid bilayer

57
Q

What kind of proteins span the membrane at least once to generate domains that localize to both sides of the membrane?

A

Transmembrane proteins

58
Q

What proteins pass through the membrane as either an amphipathic alpha-helix or a beta-sheet?

A

Transmembrane proteins

59
Q

Some membrane proteins are exposed to only one side of the membrane via what? (Two answers)

A
  1. Noncovalent interaction with other membrane proteins 2. Attachment by a carbohydrate, fatty acid or prenyl anchor
60
Q

Identify the lipid anchors

A

A. Myristoyl anchor B. Palmitoyl anchor C. Farnesyl anchor

61
Q

What type of lipid anchor contains a saturated 14 carbon fatty acid added to N-terminal glycine during translation?

A

Myristic acid

62
Q

What type of lipid anchor contains saturated 16 carbon fatty acid added to cysteine?

A

Palmitic acid

63
Q

What contains farnesyl or geranylgeranyl, has an unsaturated 15 carbon fatty acid added to C-terminal cysteine?

A

Prenyl group

64
Q

What are attached to a membrane through a fatty acid or prenyl group are often involved in converting an extracellular signal into an intracellular response

65
Q

What types of proteins are typically localized to the cytosolic side of the plasma membrane?

A

Lipid anchors

66
Q

What are reversible; converting a membrane bound protein into a soluble cytosolic one?

A

Lipid modifications

67
Q

What is this structure?

A

_-helix containing transmembrane protein

68
Q

Most membrane proteins span the lipid bilayer as what?

A

Alpha helices

69
Q

Alpha helices are composed of amino acids having what?

A

Hydrophobic side chains

70
Q

In a lipid environment these amino acids form hydrogen bonds with each other to exclude what?

71
Q

Hydrogen bonding is maximized if the polypeptide adopts what shape as it crosses the membrane?

A

Alpha helix

72
Q

On average, how many amino acids are required to cross a lipid bilayer

A

20-30 amino acids

73
Q

What plots are an example program used to predict alpha helical transmembrane domains

A

Kyte Doolittle hydropathy plots

74
Q

TheKyte Doolittle hydropathy program can not be used to identify what?

A

A beta barrel containing transmembrane regions

75
Q

The calculated hydrophobicity for a stretch of amino acids is plotted on what axis?

76
Q

The amino acid window is plotted on what axis?

77
Q

Values with a positive hydropathy score indicate what?

A

Hydrophobic regions and putative transmembrane domains

78
Q

Will this membrane protein still function normally after getting cut by the protease?

79
Q

Identify the Beta barrel proteins

A
  1. 8 stranded OmpA
  2. 12 stranded OMPLA
  3. 16 stranded porin
  4. 22 stranded FepA
80
Q

Beta barrels are composed of 8-22 antiparallel what?

A

Beta strands

81
Q

Where do you find Beta barrels?

A

Outer membrane of mitochondria, chloroplast and bacteria

82
Q

Which two Beta barrels are used for transport of small hydrophilic molecules?

83
Q

Which two Beta barrels are used for receptor or enzyme activities?

84
Q

Average length of a beta strand is how long?

A

10 amino acids

85
Q

The study of membrane proteins requires the use of various what?

A

Detergents

86
Q

Detergents cover the hydrophobic domains of membrane spanning segments generating what complexes?

A

Protein-detergent-lipid

87
Q

Detergents are what making them ideal for solubilizing the transmembrane proteins?

A

Amphiphilic

88
Q

Name the two types of detergents

A
  1. Strong ionic detergents (SDS) 2. Nonionic detergents (TritonX-100 or beta-octylglucoside)
89
Q

Which detergents completely denature proteins?

A

Strong ionic detergents (SDS)

90
Q

Which detergents are gentle and used to isolate membrane proteins in an active state?

A

Nonionic detergents (TritonX-100 or beta-octylglucoside)

91
Q

What two tests are used to measure the lateral diffusion rates of membrane proteins in a lipid bilayer?

A
  1. FRAP (fluorescence recovery after photobleaching) 2. FLIP (fluorescence loss in photobleaching)
92
Q

The rate of diffusion of membrane proteins will vary from protein to protein due to their interaction with what?

A

Other proteins and cytoskeletal elements

93
Q

FRAP and FLIP measure the bulk flow of what?

A

Membrane protein movement

94
Q

What is the limitation of both the FRAP and FLIP tests?

A

These methods can not be used to follow the movement of an individual protein molecule

95
Q

What is this structure?

A

A single-pass transmembrane protein

96
Q

What test is this? FRAP or FLIP?

97
Q

What test is this? FRAP or FLIP?

98
Q

What with its associated membrane proteins is not a free flowing sea of lipid and membrane proteins?

A

A plasma membrane

99
Q

Cells with what (apical, lateral and basal) have membrane domains with distinctly different functions?

100
Q

What is established by the asymmetric distribution of both lipid and membrane proteins?

101
Q

Differential localization is essential for what?

A

Cellular function

102
Q

Several mechanisms generate and maintain what?

A

An asymmetric distribution pattern

103
Q

What is A? It is an intercellular junction that maintains the separation of both protein and lipid molecules

A

Tight junction

104
Q

What are four mechanisms to restrict membrane protein motility?

A

Proteins can self-assemble into large aggregates

They can be tethered by interactions with assemblies of macromolecules:

  1. Outside the cell
  2. Inside the cell
  3. They can interact with proteins on the surface of another cell
105
Q

Mammalian cells have a what just below their plasma membrane?

A

A complex cytoskeletal network

106
Q

What are two functions of the actin based network?

A
  1. Restricts movement of membrane proteins that are directly linked. 2. Establishes a barrier for other membrane proteins
107
Q

The actin network is closely associated with the membrane forming a mechanical barrier for what purpose?

A

The free diffusion of other membrane proteins

108
Q

What is A?

A

An example ‘corral’ formed by cytoskeletal elements

109
Q

What is B?

A

A trace for the movement for a single membrane protein

Eukaryotic Cell Biology (7 decks)

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