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
2
Q
What did Hooke discover?
A
Cell theory
3
Q
How are prokaryote types separated ?
A
By ribosomal RNA sequences
4
Q
What are the types of prokaryotes?
A
Archaea, Eubacteria
5
Q
Describe the characteristics of gram negative prokaryotes
A
Periplasmic space, thin layer of peptidoglycan
6
Q
Describe gram positive bacteria
A
large layer of peptidogylcan
7
Q
Give an example of gram positive bacteria
A
staphyloccal, streptococcaal
8
Q
Give an example of gram negative bacteria
A
E.coli salmonella
9
Q
What is a lysosome?
A
an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membrane
10
Q
What charge do nuclei have?
A
Negative
11
Q
What does fluorescence microscopy allow?
A
Visualisation of proteins and lipids in fixed cells
12
Q
What cells have a specialised plasma membrane?
A
Rod and cone cells
13
Q
What is the key role of phosphoinositides?
A
Responding to growth factors
14
Q
What type of bonds does acetone form with water?
A
Electrostatic interactions
15
Q
Why does acetone form electrostatic interactions with water?
A
It is polar
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
17
Q
Name the features of epithelial cells
A
Highly organised cells, very motile, ALWAYS polarised, apical and basolateral domains, always exposed to environment
18
Q
What is the function of white blood cells
A
secrete antibodies
19
Q
What are acinar cells
A
exocrine cells of the pancreas
20
Q
What is the function of acinar cells
A
secrete lots of digestive enzymes to assist with digestion of food
21
Q
What are the properties of the Plasma membrane
A
Barrier and selectively permeable
22
Q
What is the PM composed of
A
Lipids, proteins and carbohydrates
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
24
Q
What are oligosaccharides?
A
carbohydrates composed of a small number of monosaccharide units
25
How are phospholipids held together?
non-covalent forces; Van der Waals and hydrogen bonding
26
Why are phospholipids amphipathic?
polar head group and hydrophobic tail
27
What is the charge of phospholipids?
Neutral
28
Why do phospholipids have a neutral charge?
Choline is positively charged and phosphate has a negative charge
29
What are the four main membrane phospholipids?
Phosphatidyl-ethanolamine
Phosphatidyl-serine
phosphatidyl-choline
Sphingo-myelin
30
Which major membrane phospholipid has a negative charge?
phosphatidyl-serine
31
TRUE or FALSE - all major membrane phospholipids have a neutral charge except phosphatidyl-serine
TRUE
32
What form do fatty acid chains normally take in nature?
Cis
33
What forms the polar head group in phospholipids
choline
34
describe cis fatty acids
have kinks/bends so cant pack closely together
35
what is lacking in bacterial membranes
cholesterol and sphingomyelin
36
What do phospholipids form in aqueous solutions
micelles or bilayers - more energetically favourable
37
What is the structure of a liposome?
spherical structure of phospholipids arranged around a water molecule
38
What the applications of liposomes?
drug delivery into cells, DNA delivery and cosmetics
39
What phospholipid movement rarely occurs
flip-flop
40
Describe the effect of cholesterol on the membrane
increases fluidity at high temperatures and decreases permeability
41
What are tetraspanins?
scaffolding proteins
42
What is the function of tetraspanins?
Anchor multiple proteins to one area of the membrane, important in the immune system
43
Describe micro-domains
Joining of proteins and lipids, thicker than the rest of the bilayer, accumulation of proteins allows rafts to stick together
44
What are the types of phospholipid movement?
Lateral diffusion, flexion, rotation, flip-flop
45
Describe lateral diffusion
rotation or exchange in the lateral plane of the membrane
46
Which phospholipid movement is the most energetically favourable
lateral diffusion
47
Describe the effect of unsaturated hydrocarbon chains with cis double bonds on the membrane
Increases fluidity
48
What is the effect of saturated hydrocarbon chains on the membrane and why
Decreases fluidity because they pack tightly together
49
What type of hydrocarbon chain increases membrane fluidity
more double bonds, shorter chains
50
What type of animals have more double bonds
cold blooded animals
51
Describe the structure of cholesterol
small polar head group, steroid ring, rigid structure
52
What does cholesterol prevent at high concentrations
congealing and crystallisation
53
What does no recovery/repopulation after fluorescence photobleaching show?
no mobility
54
What does fluorescence recovery after photobleaching allow?
measure the rate of mobility
55
What is the effect of a tethered nuclear membrane on mobility
no mobility
56
What are the types of secondary structure
alpha helix, beta sheet, random coil
57
Which way do side project in an alpha helix
outwards
58
describe the structure of beta sheets
kinked stable structures, parallel or antiparallel, polypeptide chains project above and below
59
What are the two types of protein association with the membrane?
Peripheral and integral
60
How do peripheral membrane proteins associate with the membrane?
covalently bind to lipids or associate directly with integral membrane proteins
61
How do integral membrane proteins associate with the membrane?
Insert directly via a hydrophobic domain
62
How many times do G-protein coupled receptors span the membrane?
7
63
What are the advantages of lipid anchoring on membrane proteins?
Mobility, rapid release into extracellular space, regulate binding and release of proteins to membrane
64
Proteins linked to ... move more rapidly
phosphatidylinositol
65
What bonds hold together single pass transmembrane proteins?
Disulphide bonds
66
What do hydropathy plots measure
hydrophobicity of amino acids
67
What are beta barrels function in bacteria?
pore forming proteins
68
What is the effect of detergents on membranes?
solubilise phospholipids in membranes, causes proteins to acquire a negative charge
69
What is an example of a harsh membrane detergent
sodium dodecyl sulphate
70
What is the effect of sodium dodecyl sulphate on the membrane
linearises membranes
71
what are the functions/types of integral proteins
enzymes, carriers, channels, receptors, cell-cell recognition
72
What are the functions/types of peripheral membrane proteins?
cell shape determination, communication with internal and external environment, cell signalling
73
What happens to red blood cells in a hypotonic solution?
creates RBC ghosts, form a pure preparation of the plasma membrane
74
What is SDS polyacrylamide gel electrophoresis used for
analyse proteins and separate them based on size
75
what does spectrin form
dimers
76
what is spectrin
cytoskeletal protein that lines intracellular side of PM in eukaryotic cells
77
What is spectrin important for
mechanical stability of RBCs
78
What do mutations in spectrin cause?
types of haemolytic anaemia
79
What are the peripheral proteins in RBC cytoskeleton
spectrin, actin, ankyrin
80
What are the transmembrane proteins in RBC cytoskeletons
glycophorin, band 3
81
What is the RBC biconcave shape maintained by
mesh of proteins lining inner surface of the membrane
82
What protein is NOT freely diffusible in the RBC cytoskeleton
Band 3
83
What are the restraints on protein movement
Physical structures and direct interactions with the cytoskeleton
84
What do tight junctions prevent in the PM
free diffusion in cytoplasmic leaflet and partial lipid barrier
85
What are the restraints on lipids
sequestation by binding to specific proteins, segregated into domains, physical barriers
86
What is the glycocalyx
the cell coat
87
How is the glycocalyx formed
association of sugar residues with transmembrane and peripheral proteins at extracellular surface
88
What blood group is the universal donor
O
89
What blood group is the universal acceptor
AB
90
What is blood group determined by?
structure of the oligosaccharide attached to sphingomyelin and proteins in the RBC membrane
91
What is the function of scramblase
abolish asymmetry by
| equilibrating lipids, transferring lipids and catalysing flipping of phospholipids
92
What is the NET charge on the cytoplasmic side of RBCs
negative
93
What does the net equilibrium favour under normal condition in RBCs PM
translocase
94
what is the function of translocase in RBCs PM
transfer phosphatidyl-serine from outer leaflet to the inner leaflet
95
What type of molecules can move freely across the PM
hydrophobic molecules EG O2, CO2, N2 and benzene
96
What do the rate that molecules move across the membrane depend on
charge, size and polarity
97
What type of molecules do membrane transport proteins move
solutes like sugars, amino acids, nucleotides and ions
98
What are the two main classes of membrane transport protein
carriers and channels
99
What are membrane transport proteins
multi-pass integral membrane proteins
100
What type of interaction do carriers have with the solute?
Direct interaction - binding
101
Which membrane transport protein is the fastest
channels
102
What type of interaction do channels have with the solute
weak
103
what do ion channels form
narrow hydrophilic pores through the membrane
104
What do ion channels allow
rapid movement of ions down concentration or electrical gradient
105
How do ions move through ion channels
the selectively filter means ion fit through interactions with carbonyl groups in pore
106
What are ion channels regulated by?
binding of ions, changes in voltage or binding of small molecules
107
Mutation in what channel causes congenital insensitivity to pain
SCN9A - voltage gated sodium channel
108
How do carriers transport solutes
undergo conformational change
109
What are the types of carrier?
uniport, symport and antiport
110
what creates the electrochemical gradient
membrane potential and concentration gradient
111
What is the electrochemical gradient established by?
ionic concentration differences on either side of the membrane
112
What pumps use active transport
ATP-driven pumps, light driven pumps
113
What is the uptake of glucose driven by
Electrochemical gradient of Na+
114
What type of transport moves glucose
coupled transport
115
How do sodium and potassium move by a sodium potassium ATPase
3Na+ move out, 2K+ move in
