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BMS109 Cell & Molecular > Biological Membranes > Flashcards

Biological Membranes Flashcards

Explain general properties of membranes, their functions, channels & association

1
Q

What are primordial germ cells

A

Stem cells that make reproductive gametes

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2
Q

What did Hooke discover?

A

Cell theory

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3
Q

How are prokaryote types separated ?

A

By ribosomal RNA sequences

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4
Q

What are the types of prokaryotes?

A

Archaea, Eubacteria

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5
Q

Describe the characteristics of gram negative prokaryotes

A

Periplasmic space, thin layer of peptidoglycan

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6
Q

Describe gram positive bacteria

A

large layer of peptidogylcan

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7
Q

Give an example of gram positive bacteria

A

staphyloccal, streptococcaal

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8
Q

Give an example of gram negative bacteria

A

E.coli salmonella

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9
Q

What is a lysosome?

A

an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membrane

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10
Q

What charge do nuclei have?

A

Negative

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11
Q

What does fluorescence microscopy allow?

A

Visualisation of proteins and lipids in fixed cells

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12
Q

What cells have a specialised plasma membrane?

A

Rod and cone cells

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13
Q

What is the key role of phosphoinositides?

A

Responding to growth factors

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14
Q

What type of bonds does acetone form with water?

A

Electrostatic interactions

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15
Q

Why does acetone form electrostatic interactions with water?

A

It is polar

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16
Q

What type of bond does 2-methyl propane form with water and why?

A

none - non-soluble so forms a crystalline ice cage due to non-polarity

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17
Q

Name the features of epithelial cells

A

Highly organised cells, very motile, ALWAYS polarised, apical and basolateral domains, always exposed to environment

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18
Q

What is the function of white blood cells

A

secrete antibodies

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19
Q

What are acinar cells

A

exocrine cells of the pancreas

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20
Q

What is the function of acinar cells

A

secrete lots of digestive enzymes to assist with digestion of food

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21
Q

What are the properties of the Plasma membrane

A

Barrier and selectively permeable

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22
Q

What is the PM composed of

A

Lipids, proteins and carbohydrates

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23
Q

What carbohydrates is the PM composed of and how do they bond?

A

Glycoproteins and glycolipids that covalently link to proteins and lipids

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24
Q

What are oligosaccharides?

A

carbohydrates composed of a small number of monosaccharide units

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25
Q

How are phospholipids held together?

A

non-covalent forces; Van der Waals and hydrogen bonding

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26
Q

Why are phospholipids amphipathic?

A

polar head group and hydrophobic tail

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27
Q

What is the charge of phospholipids?

A

Neutral

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28
Q

Why do phospholipids have a neutral charge?

A

Choline is positively charged and phosphate has a negative charge

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29
Q

What are the four main membrane phospholipids?

A

Phosphatidyl-ethanolamine
Phosphatidyl-serine
phosphatidyl-choline
Sphingo-myelin

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30
Q

Which major membrane phospholipid has a negative charge?

A

phosphatidyl-serine

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31
Q

TRUE or FALSE - all major membrane phospholipids have a neutral charge except phosphatidyl-serine

A

TRUE

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32
Q

What form do fatty acid chains normally take in nature?

A

Cis

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33
Q

What forms the polar head group in phospholipids

A

choline

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34
Q

describe cis fatty acids

A

have kinks/bends so cant pack closely together

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35
Q

what is lacking in bacterial membranes

A

cholesterol and sphingomyelin

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36
Q

What do phospholipids form in aqueous solutions

A

micelles or bilayers - more energetically favourable

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37
Q

What is the structure of a liposome?

A

spherical structure of phospholipids arranged around a water molecule

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38
Q

What the applications of liposomes?

A

drug delivery into cells, DNA delivery and cosmetics

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39
Q

What phospholipid movement rarely occurs

A

flip-flop

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40
Q

Describe the effect of cholesterol on the membrane

A

increases fluidity at high temperatures and decreases permeability

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41
Q

What are tetraspanins?

A

scaffolding proteins

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42
Q

What is the function of tetraspanins?

A

Anchor multiple proteins to one area of the membrane, important in the immune system

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43
Q

Describe micro-domains

A

Joining of proteins and lipids, thicker than the rest of the bilayer, accumulation of proteins allows rafts to stick together

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44
Q

What are the types of phospholipid movement?

A

Lateral diffusion, flexion, rotation, flip-flop

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45
Q

Describe lateral diffusion

A

rotation or exchange in the lateral plane of the membrane

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46
Q

Which phospholipid movement is the most energetically favourable

A

lateral diffusion

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47
Q

Describe the effect of unsaturated hydrocarbon chains with cis double bonds on the membrane

A

Increases fluidity

48
Q

What is the effect of saturated hydrocarbon chains on the membrane and why

A

Decreases fluidity because they pack tightly together

49
Q

What type of hydrocarbon chain increases membrane fluidity

A

more double bonds, shorter chains

50
Q

What type of animals have more double bonds

A

cold blooded animals

51
Q

Describe the structure of cholesterol

A

small polar head group, steroid ring, rigid structure

52
Q

What does cholesterol prevent at high concentrations

A

congealing and crystallisation

53
Q

What does no recovery/repopulation after fluorescence photobleaching show?

A

no mobility

54
Q

What does fluorescence recovery after photobleaching allow?

A

measure the rate of mobility

55
Q

What is the effect of a tethered nuclear membrane on mobility

A

no mobility

56
Q

What are the types of secondary structure

A

alpha helix, beta sheet, random coil

57
Q

Which way do side project in an alpha helix

A

outwards

58
Q

describe the structure of beta sheets

A

kinked stable structures, parallel or antiparallel, polypeptide chains project above and below

59
Q

What are the two types of protein association with the membrane?

A

Peripheral and integral

60
Q

How do peripheral membrane proteins associate with the membrane?

A

covalently bind to lipids or associate directly with integral membrane proteins

61
Q

How do integral membrane proteins associate with the membrane?

A

Insert directly via a hydrophobic domain

62
Q

How many times do G-protein coupled receptors span the membrane?

A

7

63
Q

What are the advantages of lipid anchoring on membrane proteins?

A

Mobility, rapid release into extracellular space, regulate binding and release of proteins to membrane

64
Q

Proteins linked to … move more rapidly

A

phosphatidylinositol

65
Q

What bonds hold together single pass transmembrane proteins?

A

Disulphide bonds

66
Q

What do hydropathy plots measure

A

hydrophobicity of amino acids

67
Q

What are beta barrels function in bacteria?

A

pore forming proteins

68
Q

What is the effect of detergents on membranes?

A

solubilise phospholipids in membranes, causes proteins to acquire a negative charge

69
Q

What is an example of a harsh membrane detergent

A

sodium dodecyl sulphate

70
Q

What is the effect of sodium dodecyl sulphate on the membrane

A

linearises membranes

71
Q

what are the functions/types of integral proteins

A

enzymes, carriers, channels, receptors, cell-cell recognition

72
Q

What are the functions/types of peripheral membrane proteins?

A

cell shape determination, communication with internal and external environment, cell signalling

73
Q

What happens to red blood cells in a hypotonic solution?

A

creates RBC ghosts, form a pure preparation of the plasma membrane

74
Q

What is SDS polyacrylamide gel electrophoresis used for

A

analyse proteins and separate them based on size

75
Q

what does spectrin form

A

dimers

76
Q

what is spectrin

A

cytoskeletal protein that lines intracellular side of PM in eukaryotic cells

77
Q

What is spectrin important for

A

mechanical stability of RBCs

78
Q

What do mutations in spectrin cause?

A

types of haemolytic anaemia

79
Q

What are the peripheral proteins in RBC cytoskeleton

A

spectrin, actin, ankyrin

80
Q

What are the transmembrane proteins in RBC cytoskeletons

A

glycophorin, band 3

81
Q

What is the RBC biconcave shape maintained by

A

mesh of proteins lining inner surface of the membrane

82
Q

What protein is NOT freely diffusible in the RBC cytoskeleton

A

Band 3

83
Q

What are the restraints on protein movement

A

Physical structures and direct interactions with the cytoskeleton

84
Q

What do tight junctions prevent in the PM

A

free diffusion in cytoplasmic leaflet and partial lipid barrier

85
Q

What are the restraints on lipids

A

sequestation by binding to specific proteins, segregated into domains, physical barriers

86
Q

What is the glycocalyx

A

the cell coat

87
Q

How is the glycocalyx formed

A

association of sugar residues with transmembrane and peripheral proteins at extracellular surface

88
Q

What blood group is the universal donor

A

O

89
Q

What blood group is the universal acceptor

A

AB

90
Q

What is blood group determined by?

A

structure of the oligosaccharide attached to sphingomyelin and proteins in the RBC membrane

91
Q

What is the function of scramblase

A

abolish asymmetry by

equilibrating lipids, transferring lipids and catalysing flipping of phospholipids

92
Q

What is the NET charge on the cytoplasmic side of RBCs

A

negative

93
Q

What does the net equilibrium favour under normal condition in RBCs PM

A

translocase

94
Q

what is the function of translocase in RBCs PM

A

transfer phosphatidyl-serine from outer leaflet to the inner leaflet

95
Q

What type of molecules can move freely across the PM

A

hydrophobic molecules EG O2, CO2, N2 and benzene

96
Q

What do the rate that molecules move across the membrane depend on

A

charge, size and polarity

97
Q

What type of molecules do membrane transport proteins move

A

solutes like sugars, amino acids, nucleotides and ions

98
Q

What are the two main classes of membrane transport protein

A

carriers and channels

99
Q

What are membrane transport proteins

A

multi-pass integral membrane proteins

100
Q

What type of interaction do carriers have with the solute?

A

Direct interaction - binding

101
Q

Which membrane transport protein is the fastest

A

channels

102
Q

What type of interaction do channels have with the solute

A

weak

103
Q

what do ion channels form

A

narrow hydrophilic pores through the membrane

104
Q

What do ion channels allow

A

rapid movement of ions down concentration or electrical gradient

105
Q

How do ions move through ion channels

A

the selectively filter means ion fit through interactions with carbonyl groups in pore

106
Q

What are ion channels regulated by?

A

binding of ions, changes in voltage or binding of small molecules

107
Q

Mutation in what channel causes congenital insensitivity to pain

A

SCN9A - voltage gated sodium channel

108
Q

How do carriers transport solutes

A

undergo conformational change

109
Q

What are the types of carrier?

A

uniport, symport and antiport

110
Q

what creates the electrochemical gradient

A

membrane potential and concentration gradient

111
Q

What is the electrochemical gradient established by?

A

ionic concentration differences on either side of the membrane

112
Q

What pumps use active transport

A

ATP-driven pumps, light driven pumps

113
Q

What is the uptake of glucose driven by

A

Electrochemical gradient of Na+

114
Q

What type of transport moves glucose

A

coupled transport

115
Q

How do sodium and potassium move by a sodium potassium ATPase

A

3Na+ move out, 2K+ move in

BMS109 Cell & Molecular (26 decks)

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