chapter 12 lipids and membranes Flashcards
(310 cards)
1
Q
Lipids are a very diverse set of molecules related how?
A
By their hydrophobic properties
2
Q
What are the hydrophobic properties of lipids?
A
- not appreciably soluble in water
- soluble in organc solvents
- waxy, greasy or oily compounds in plants and animals.
3
Q
Are lipids soluble in water?
A
Not appreciably soluble
4
Q
Are lipids soluble in chloroform (CHCl3)?
A
yes because its an organic solvent
5
Q
Are lipids soluble in methanol (CH3OH)?
A
yes because it is an organic solvent
6
Q
How is lipid formation different than other biomolecules
A
Lipids form large aggregates, but not polymers like other biomolecules.
7
Q
What are function of lipids?
A
Functions are diverse:
- Storage of energy
- Structure of cell membranes
- Signaling and other biological activities
8
Q
What are the two main categories of classifying lipids?
A
1) Saponifiable
2) Non-saponifiable
9
Q
What are Saponifiable?
A
Ester-containing compounds
10
Q
What are non-saponifiable?
A
Does NOT contain an ester group and are NOT capable of being hydrolyzed
11
Q
Steroids are an example what type of lipid?
A
Non-saponifiable thus not able to be hydrolyzed
12
Q
Eicosanoids are an example of what type of lipids?
A
Non-saponifiable thus not hydrolyzed
13
Q
Sphingolipids are an example of what type of lipid?
A
Saponifiable meaning it contains an ester containing compounds
14
Q
Glycerophospholipids are an example of what type of lipid?
A
Saponifiable; meaning it contains an ester containing compounds
15
Q
Triacylglycerides are an example of what type of lipid?
A
Saponifiable; meaning it contains ester containing compounds
16
Q
What are fatty acids?
A
carboxylic acids with long-chain hydrocarbon side groups
17
Q
/\/\/\/\/\/\/\/\/\/\/\/\/COOH
is an example of what type of lipid?
A
fatty acid (non polar tail and polar head)
18
Q
Is the polar head of a fatty acid soluble? if so under what conditions?
A
yes at physiological pH (7.4)
19
Q
If a fatty acid has a polar head of COOH and is in water at physiological pH (7.4) what dominates?
A
carboxylate ion (COO-) dominates
20
Q
What are the common characteristics of fatty acids?
A
- tails are usually straight
- most range from 10-20 carbons
- Usually even # carbons
21
Q
Are fatty acids saturated, unsaturated or polysaturated?
A
all of the above
22
Q
Most unsaturated fatty acids have hat type of configuration?
A
almost always cis-isomers
23
Q
Common name: Lauric acid has a systemic name of what?
A
dodecanoic acid
24
Q
Dodecanoic acid is also called what?
A
Lauric acid
25
What is the structure of Dodecanoic acid (Lauric acid)?
CH3(CH2)10COOH
26
What is the melting point of Dodecanoic acid (Lauric acid)?
44.2 degrees C
27
What is the systemic name of Myristic acid?
Tetradecanoic acid
28
Tetradecanoic acid is also called what?
Myristric acid
29
What is the structure of Tetradecanoic acid (Myristic acid)?
CH3(CH2)12COOH
30
What is the melting point of Tetradecanoic acid (Myristic acid)?
53.9 degrees C
31
What is the systemic name for Palmitic acid?
Hexadecanoic acid
32
What is the common name for Hexadecanoic acid?
Palmitic acid
33
What is the structure of Hexadecanoic acid (Palmitic acid)?
CH3(CH2)14COOH
34
What is the melting point of Hexadecanoic acid (palmitic acid)
63.1 degrees C
35
What is systemic name for Stearic acid?
Octadecanoic acid
36
What is the common name for Octadecanoic acid?
Stearic acid
37
What is the structure for Octadecanoic acid (Steric acid)?
CH3(CH2)16COOH
38
What is the melting point of Octadecanoic acid (Steric acid)?
69.6 degrees C
39
What is the systemic name for Palmitoleic acid?
9-Hexadecanoic acid
40
What is the common name for 9-Hexadecanoic acid?
Palmitoleic acid
41
What type of lipid is Hexadecanoic acid (Palmitic acid)?
Fatty acid
42
What type of lipid is Dodecanoic acid (Lauric acid)?
Fatty acid
43
What type of lipid is Tetradecanoic acid (Myristic acid)?
Fatty acid
44
What type of lipid is Octadecanoic acid (Steric acid)?
Fatty acid
45
What is the structure of 9-Hexadecanoic acid (Palmitoleic acid)?
CH3(CH2)CH=CH(CH2)7COOH
46
What is the melting point of 9-Hexadecanoic acid (Palmitoleic acid)?
-0.5 degrees C
47
What is the systemic name for Oleic acid
9-Octadecanoic acid
48
What is the common name for 9-Octadecanoic acid
Oleic acid
49
What is the structure of 9-Octadecanoic acid (oleic acid)?
CH3(CH2)CH=CH(CH2)COOH
50
What is the melting point of 9-Octadecanoic acid (oleic acid)?
12 degrees C
51
Is Hexadecanoic acid (Palmitic acid) a saturated or unsaturated fatty acid?
saturated acid
52
Is type of lipid is Dodecanoic acid (Lauric acid) a saturated or unsaturated fatty acid?
Saturated acid
53
Is Tetradecanoic acid (Myristic acid) a saturated or unsaturated fatty acid?
saturated
54
Is Octadecanoic acid (Steric acid) a saturated or unsaturated fatty acid?
Saturated
55
Is 9-Octadecanoic acid (oleic acid) a saturated or unsaturated fatty acid?
unsaturated fatty acid in cis
56
Is 9-Hexadecanoic acid (Palmitoleic acid) a saturated or unsaturated fatty acid?
Unsaturated fatty acid in cis
57
what is the systemic name for Linoleic acid?
9, 12 Octadecadienoic acid
58
What is the common name for 9, 12 Octadecadienoic acid?
Linoleic acid
59
Is 9, 12 Octadecadienoic acid (Linoleic acid) a saturated or unaturated fatty acid?
unsaturated fatty acid in cis
60
What is the structure of 9, 12 Octadecadienoic acid (Linoleic acid)?
CH3(CH2)4(CH=CHCH2)2(CH2)6COOH
61
What is the melting point of 9, 12 Octadecadienoic acid (Linoleic acid)?
-5 degrees C
62
What is the systemic name for alpha-Linolenic acid?
9, 12, 15 Octadecatrienoic acid
63
What is the common name for 9, 12, 15 Octadecatrienoic acid?
alpha-Linolenic acid
64
What is the structure of 9, 12, 15 Octadecatrienoic acid (alpha-Linolenic acid)?
CH3CH2(CH=CHCH2)3(CH2)6COOH
65
What is the melting point of 9, 12, 15 Octadecatrienoic acid (alpha-Linolenic acid)?
-11 degrees C
66
Is 9, 12, 15 Octadecatrienoic acid (alpha-Linolenic acid) a saturated or unsaturated fatty acid?
Unsaturated fatty acid in cis
67
How many double bonds does a saturated fatty acid?
No double bonds
68
What type of fatty acids has double bonds?
unsaturated fatty acids
69
How are unsaturated fatty acid biosynthesized in eukaryotes?
Biosynthesized in eukaryotes from corresponding saturated fatty acids by an aerobic process.
70
Linoleic acid and linolenic acid is found where?
plants and fish oils
71
Linoleic acid and linolenic acid are necessary for what?
regulating blood pressure, clotting, lipid levels, immune response, and inflammation response
72
Triglycerides from animals are _____ at room temperature and called what?
Triglycerides from animals are solid at room temperature and called fats
73
Triglycerides from plants and fish are _____ at room temperature and called _____
Triglycerides from plants and fish are liquids at room temperature and called oils.
74
Phospholipases disrupts what?
disrupts membranes
75
Bees and snake venom makes a lot of what?
Phospholipase A2
76
Sphingomyelin is what type of lipid?
sphingolipids
77
Sphingomyelin has what two components?
1) phosphocholine head group
| 2) Palmitate residue
78
Sphingomyelin makes up 10-20% of what?
Plasma membrane
79
Sphingomyelin is the primary component of what?
myelin sheath
80
Springosine's N-acyl fatty acid derivative is called what?
ceramides
81
sphingolipids are derviatives of what?
C18 amino alcohols sphingosine, dihydrosphingosine and their C16, C17 C19 and C20 homologs.
82
Ceramides occur only in small amounts in ______ but form the parent compound of the more abundant ______
Ceramides occur only in small amounts in plants and animal tissues but form the parent compounds of more abundant sphingolipids.
83
What is the most common sphingolipids?
Sphingomyelins
84
Sphingomyelins contain what?Thus are considered sphingophospholipids.
bear a ceramide bearing either a phosphocholine or a phosphoethanolamine moiety.
85
the myelin sheath of nerve cells is rich in what?
sphingomyelin
86
What is the simplest sphingolipid?
Cerebrosides or AKA glucosphingolipids
87
Cerebrosides are also called what?
glucosphingolipids
88
Cerebrosides are what?
Ceramides with head groups consisting of a single sugar residue
89
Galactocerebrosides have a head group of what?
Beta-D-galactose
90
Galactocerbosides are most prevalent where?
neuronal cell membranes
91
cerebrosides lack what group?
phosphate group
92
Glucocerebrosides have what type of head?
Beta-D-glucose
93
Glucocerbrosides occur where?
In the membranes of other tissues.
94
What group does phospholipids have cerbrosides lack? Making cebrosides what?
phosphate group making cerebrosides the most frequent nonionic compounds.
95
The galactose residue of some galactocerebrasides are _____ at what position to form ionic compounds called what?
are sulfated at C3 position to form ionic compounds called sulfatides.
96
More complex sphingoglycolipids have what?
unbranched oligosaccharides head groups of up to four sugar residues
97
What are the three types of sphingolipids
1) sphingomyelin
2) Cerebrosides
3) Gangliosides
98
What is the most complex group of sphingolipids?
Gangliosides
99
Gangliosides have what types of significance?
physiological and medical
100
Gangliosides are the primary components of what?
cell surface membranes
101
Gangliosides constitute a significant fraction of ____ lipids?
brain lipids (6%)
102
Gangliosides act as what for toxins?
receptors
103
What is the structure of Gangliosides?
ceramide oligosaccharides that include atleast one sialic acid residue (N-acetylneuraminic acid and its derivatives).
104
How does complex carbohydrate head groups of gangliosides act?
Their complex carbohydrate head groups, which extend beyond the surfaces of cell membranes, act as specific receptors for certain pituitary glycoprotein hormones that regulate a number of physiological functions.
105
Disorders of ganglioside break down are responsible for what type of hereditary disesease? which are characterized how?
Sphingolipid storage diseases such as Tay-Sachs disease which are characterized by an invariably fatal neurological deterioration.
106
GM1 Gangliosides include?
- > D-Galactose
- > N-Acetyl-D-galactosamine
- > D-Galactose
- > D-Glucose
107
GM2 gangliosides include?
- > N-Acetyl-D-galactosamine
- > D-Galactose
- > D-Glucose
108
GM3 gangliosides
- > D-Galactose
| - > D-Glucose
109
Gangliosides are specific determinants of cell-cell recognition so they have inportant role in what?
growth and differentiation of tissues as well as in carcinogens (cancer generation).
110
What is the most common steroid in animals?
Cholesterol
111
What is the metabolic precursor to steroid hormones?
cholesterol
112
Steroids are derivatives of what?
cyclopentanoperhydrophenanthrene
113
Cholesterol is classified as what? why?
sterol because of its C3-OH group and its branched aliphatic side chain of 8 to 10 carbon atoms at C17.
114
Cholesterol is a major component of what? Present at what mol %.
animal plasma membranes which typically is present at 30-40 mol%
115
Cholesterol is present in lesser amount than 30-40 mol% in the membranes or what?
membranes of animal sub-cellular organelles.
116
What gives cholesterol its weak amphiphilic character?
Its polar OH group
117
What gives cholesterol its rigidity which is greater than other membrane lipids?
its fused ring system.
118
Cholesterol is abundant is _____ in which ~70% is esterified to what?
abundant in blood plasma lipoproteins where ~ 70% of it is esterified to long-chain fatty acids to form cholesteryl esters.
119
steroid hormaones regualte what?
a great variety of physiological functions including sexual development and carbohydrate metabolism.
120
plants contain little cholesterol but rather their most common sterol membrane components are what?
stigmasterol and Beta-sitosterol.
121
How does cholesterol differ fro, stigmasterol and Beta-sitosterol?
differ only in their aliphatic side chain.
122
Yeast and fungi have the sterol _____ which has what structure?
erosterol which has a C7 to C8 double bond.
123
Prokaryotes except for mycoplasmas contain what sterol?
little if any sterol
124
Gluccorticoids are what?
sterois used for biomolecule metabolism that deal with inflammation and stress
125
Mineralocorticoids are what?
steroids that deal with kidney osmosis (salt/water balance)
126
Androgens and estrogens are what?
steroids that deal with sexual development and function
127
Vitamin D is what?
a steroid hormone
128
What are the actions of Eicosinoids?
- blood pressure
- Coagulation
- pain
- fever
129
What are liposomes?
closed. self-sealing, solvent-filled vesicles
130
The fluidity of lipid bilayer is ____ dependent and a function of ______ composition?
temperature dependent and a function of membrane composition (chain length and unsaturated)
131
Biological membranes are composed of what?
phospholipods, cholosterol and proteins
132
Phospholipids are made up of?
phosphoglycerides and sphingolipids
133
what are membrane associated proteins?
- integral
- lipid linked
- peripheral
134
The protein/lipid ration in nerve cells is
0.23
135
The protein/lipid ration in protein rich membrane is
3.2
136
what is sonication?
agitation by ultrasonic vibrations
137
what are liposomes?
phospholipids suspeneded in water that are sonicated transforming them from lipid bilayer to a liposome.
138
what forms lipid bilayers and liposomes?
glycerolphospholipids
139
What is the structure of oil on water?
a monomolecular layer on the surface of water form in which the polar heads of the amphiphilic oil molecules are immersed in the water and their hydrophobic tails extend into the air.
140
What is oils effect on water?
calming effect because it largely reduced water's surface tension due to oil's weak intermolecular cohesion character of hydrocarbons rather than the strong interactions of water. Only calms smaller waves does not affect larger swells
141
In aqueous solutions amphiphilic molecules like soaps and detergents form what?
micelles (globular aggregates whose hydrocarbons are not in contact with water).
142
What does the micelles arrangement accomplish?
eliminate unfavorable contact between water and the hydrophobic tails of the amphiphiles yet permits the solvation of polar head groups.
143
How is micelle formation a cooperative process?
An assembly of just a few amphiphiles will not shield its tails from contact with water.
144
When do dilute aqueous solutions of amphiphiles form micelles?
When their concentration surpasses a certain critical micelle concentration (cmc).
145
what is the value of critical micelle concentrations needed to form a micelle?
depends on the identity of the amphiphile and solution conditions. For relatively small single tail this value is around ~1mM while for biological lipids with two large hydrophobic tails this value is generally less than 10^-6 M.
146
what type of micelles do single-tailed amphiphiles such as soap anions form?
spheroidal or ellipsoidal micelles because of their conical shapes (their hydrated head group are wider than their tails).
147
Why do most amphilphiles that form a micelle have a narrow range of the number of amphilphiles?
Too few would expose the hydrophobic core while too many would give the micelle an energetically unfavorable hollow center filled with water. The large micelle could flatten out to eliminate hollow center but the resulting decrease of curvature at the flattened surfaces would also generate empty space filled with water.
148
What types of lipids form lipid bilayers and liposomes?
Glycerophospholipids and sphingolipids
149
What are the difference between the molecules that make up bilayers/liposomes an micelles?
Micelles are single tailed while liposome/bilayers have 2 tails
150
Why are the amphiphiles more orless cylindrical in shape than micelles?
Because of the 2 hydrocarbon tails of glycerophospholipids and sphingolipids; the steric requirements of packing such molecules together yeilds a large disk like micelles that are extended biomolecular leaflets.
151
Lipid bilayers are extremely impermeable to what?
ionic and polar substance
152
How does lipid bilayer permeability of ionic and polar substances change? which suggest what?
the permeability of such substances increase with their solubilities in nonpolar solvents; which suggest that to penetrate a lipid bilayer a solute molecule must shed its hydration shell and become solvated the bilayer's hydrocarbon core.
153
Why are polar molecules so impermeable to mipid bilayers?
to penetrate a lipid bilayer a solute molecule must shed its hydration shell and become solvated the bilayer's hydrocarbon core. This process is highly unfavorable for polar molecules.
154
Lipid bilayers are appreciably permeable to what? why?
water despite its polarity its small molecular size makes it significantly soluble in the hydrocarbon core of lipid bilayers and therefore able to permeate them.
155
Liposomes are promising vehicles for what? why?
delivering therapeutic agents, such as drugs, enzymes and genes s(for gene therapy) to particular tissues because their impermeability to many substances.
156
How are liposomes absorbed by many cells?
through fusion with their plasma membranes.
157
What type of lipsosome-delivered drugs are used currently?
some anti cancer agents and antibiotics
158
How are lipid molecules transferred across a bilayer?
transverse diffusion/ flip flop (which is a rare event)
| Or lateral diffussion
159
what is transverse diffusion/flip flop and why is it such a rare event?
one way to transfer lipid molecules across a bilayer; flip flop requires the polar head groups of the lipid to pass through the hydrocarbon cor e of the bilayer. The half time of a flip flop event are minimally several days.
160
the bilayer is a ____ dimensional fluid which the hydrocarbon chains undergo what?
a 2 dimensional fluid which the hydrocarbons undergo rapid fluxional (continously changing) motion involving rotations about their C-C bonds.
161
The lateral diffusion rate of lipids molecules is quantitatively determined from what?
rate of fluorescence recovery after photobleaching(FRAP) as well as magnetic resonance measurements.
162
Molecular dynamic simulations of lipid bilayers indicate that their lipid tails are what?
highly conformationally mobile due to rotation about their C-C bonds.
163
How is the viscosity of lipid tails different at different parts of the tail?
The viscosity of these tails sharply increases closer to the lipid head groups because of their lateral mobilities are more constrained by interactions with the more rigid head groups.
164
The methyl ends of the tails from the opposite leaflet of the bilayer frequently do what instead of forming entirely separate layers? why?
are frequently interdigitated; particularly in biological membranes because their various lipids have different lengths and/or kinked due to the presence of double bonds.
165
In lipid bilayers is all the water on top of the lipid bilayer (polar heads)?
No; water molecules commonly penetrate well below the level of the head group and glycerol residues.
166
A lipid bilayer typically consists of what?
- ~30 A thick hydrocarbon core
- core bounded on both sides by ~15 A thick interface regions containing rapidly fluctuating glmoerations of head groups, water, glycerol, carbonyl and methylene groups
167
When a lipid bilayer cools below a characteristic transition temperature what happens?
It undergoes a phase change termed as order-disorder transition in which it becomes a gel-like solid; loses fluidity and hydrocarbons in chain become fully extended and packed in a hexagonal array as in crystalline paraffins.
168
What is the tansition temperature of a bilayer?
vaires but typically in the range of 10-40 degrees C; increases with chain length and degree of saturation of its component fatty acid residues
169
what is the melting temperature of a bilayer?
vaires; increases with chain length and degree of saturation of its component fatty acid residues.
170
Cholesterol does what to membrane fluidity?
decreases membrane fluidity near the membrane surface.
171
Why does cholesterol affect membrane fluidity the way it does?
decreases membrane fluidity at membrane surface because cholesterol's rigid steroid ring system interferes with the motions of the fatty acid tails causing them to be more ordered.
172
Does cholesterol spread through all the way through a lipid bilayer? what is this effect?
No it does not extend as far into a membrane as most lipids; It thus acts as a spacer that facilitates the increased mobility of fatty acids near the methyl ends.
173
How does cholesterol affect membrane temperature range of order-disorder transition? Why?
Broadens it and in high concentrations completely abolishes it; because cholesterol inhibits crystallization (cooperative aggregation into ordered arrays) of fatty acids by fitting between them.
174
Cholesterol acts as _____
membrane plasticizer
175
The transition temperatures of mammalian membranes are well below what?
body temperature and hence all have fluid character
176
Why is fluidity of biological membranes important?
allows embedded proteins to interact
177
Bacteria and poikilothermic (cold-blooded) animals such as fish do what to their fatty acid compositions of membrane lipids? How?
modify thheir fatty acid compositions of membrane lipids with ambient temperature via lipid biosynthesis and degradation to maintain membrane fluidity.
178
Most membranes are atleast ____ proteins except _____.
half proteins except for myelin membrane which is only 18% protein.
179
Membrane proteins are operationally classified according to what?
How tightly they are associated with membranes
1) Integral or intrinsic proteins
2) Peripheral or extrinsic proteins
180
Integral proteins are what?
tightly bound to membranes by hydrophobic forces and can only be separated by treatment with agents that disrupt membranes
181
How can Integral proteins be separated from the membrane?
treatment with agents that disrupts membranes such as detergents, organic solvents, chaotropic agents (ions that disrupt water structure).
182
What is Sodium dodecyl sulfate (SDS)?
a detergent used to disrupt membranes
183
What is polyoxyethylenelauryl ether?
a detergent used to disrupt membranes
184
What is polyoxyethylene-p-isooctylphenyl ether>
A detergent used to disrupt membranes.
185
What is butanol an example of?
water-miscible organic solvent used to disrupt membranes
186
What is glycerol an example of?
water-miscible organic solvent used to disrupt membranes
187
What are peripheral or extrinsic proteins?
proteins that bind to the surface of membrane by binding to the lipid head group or its integral proteins through electrostatic or hydrogen binding interactions.
188
Membrane free peripheral proteins behave how?
as water-soluble globular proteins and can be purified as such
189
How are peripheral or extrinsic proteins dissociated from membranes?
By mild procedures that leave the membrane intact such as exposure to high ionic salt solutions (such as 1M NaCl), metal chealating agents or pH changes.
190
Treating a membrane with 1 M NaCl does what?
causes its peripheral proteins to dissociate but leaves the membrane intact.
191
Integral proteins are ______ orientated amphiphiles?
asymmetrically orientated
192
The location of integral proteins on a membrane may be determined how?
through surface labeling, a technique employing agents that react with proteins but cannot penetrate membranes.
193
An integral protein on the outer surface of an intact cell membrane binds _____
antibodies elicited against it
194
An internal protein on the membrane's inner surface can bind antibodies if what?
only if the membrane has been ruptured.
195
some integral proteins are exposed to a specific surface of a membrane whereas others known as _____ do what?
transmembrane proteins span the membrane
196
How many proteins are known to be completely buried in a membrane?
None all have some exposure to the aqueous environment.
197
what does it mean that the integral protein is asymmetrical?
a particular membrane is invariably located on only one particular face of a membrane or in the case of a transmembrane protein, orientated in only one direction with respect to the membrane; Thus the oligosaccharides are located only one one side of teh integral protein exposed.
198
Integral proteins are amphiphilic how?
the proteins segments immersed in a membrane's nonpolar interior have predominately hydrophobic surface residues whereas those portions that extend into the aqueous environment are by and large sheathed with polar residues.
199
The transmembrane domain as is common in many integral proteins forma what?
alpha helix
200
Is glycine polar or nonpolar?
nonpolar
201
Is alanine polar or nonpolar?
nonpolar
202
Is valine polar or nonpolar?
nonpolar
203
Is Leucine polar or nonpolar?
nonpolar
204
Is Isoleucine polar or nonpolar?
nonpolar
205
Is Methionine polar or nonpolar?
nonpolar
206
Is proline polar or nonpolar?
nonpolar
207
Is phenylalanine polar or nonpolar?
nonpolar
208
Is Tryptophan polar or nonpolar?
nonpolar
209
G is
Glycine
210
A is
alanine
211
V is
valine
212
L is
Leucine
213
I is
Isoleucine
214
M is
Methionine
215
P is
proline
216
F is
phenylanine
217
W is
Tryptophan
218
In many integral proteins the hydrophobic segments does what?
anchors the active region of the protein to the membrane.
219
Trypsin does what to membrane bound enzyme cytochrome b5?
cleaves the membrane-bound enzyme cytochrome b5 into a polar, enzymatically active ~85 residue N-terminal fragment and an ~50 residue C-terminal fragment that remains embedded in the membrane.
220
How can you predict the position of transmembrane helix
It is going to be the largest peak; more than 85 kJ*mol-1 of free energy.
221
The asymmetric orientation of integral proteins in the membrane is maintained how?
by their infinitesimal flipflop rates (even slower than those of lipids) which results from the greater sizes of the membrane protein "head groups" in comparison to those of lipids
222
Are transmembrane proteins purely noonpolar
no has polar and non polar regions
223
what type of protein is a transporter protein
Integral protein
224
Bacteriorhodopsin (BR) is from where?
from the halophilic (salt loving) bacterium Halobacterium salinarium that inhabits salty place like the Dead sea.
225
Bacteriorhodopsin contains how many hydrophobic helical rods?
7 hydrophobic helical rods
226
Bacteriohodopsin is a _______ residue protein that does what?
247 residue protein is a light-driven proton pump; it generates a proton concentration gradient across the membrane that power the synthesis of ATP.
227
Bacteriorhodopsin's light-absorbing element, ______, is covalently bound to what?
light-absorbing element, retinal, is covalently bound to its Lys 216
228
Retinal is a _____ which is responsible for bacteriorhodopsin membrane's ______ color and is also the light sensitive element of what?
Retinal is a chromophore (light-absorbing group) which is responsible for the membrane's purple color and is the light sensitive element of vision
229
Under low O2 conditions bacteriorhodopsin develops what?
wide patches of purple membrane whose protein component is bacteriohodopsin (BR)
230
The purple membrane of bacteriohodopsin is _____% protein and ____% lipid
75% protein and 25% lipids
231
A membrane's bacteriohodopsin (BR) molecules are arranged how?
IN a highly ordered 2-D array (a 2-D crystal)
232
Bacteriohodopsin forms what type of trimer?
homotrimer
233
Each of the 7 hydrophobic alpha helical rods of Bacteriohodopsin consist of what?
of approximately 25-residue alpha helical rods that each span the lipid bilayer in directions almost perpendicular to the bilayer plane.
234
Bacteriohodopsin is _____ topic
polytopic (multispanning); span the lipid bilayer
235
The ~20 A spaces between the protein molecules in the purple membrane are occupied by what?
the lipid bilayer
236
Adjacent alpha helices which are largely _____ in character are connected ______
hydrophobic in character; connected in head-to-tail fashion by short polypeptide loops.
237
What type of residue will be found in the exterior of integral membrane?
uncharged polar
238
Serine is?
uncharged polar
239
Threonine is?
uncharged polar
240
Asparagine is?
uncharged polar
241
Glutamine is?
uncharged polar
242
Tyrosine is?
uncharged polar
243
Cysteine is?
uncharged polar
244
S is
Ser
245
T is
Threonine
246
N is
Asparagine
247
Q is
Glutamine
248
Y is
Tyrosine
249
C is
Cysteine
250
Where are the charged residues of the Alpha helices of bacteriorhodopsin located? Is this the same as other membrane pumps and channels?
protein charged residues near the surface of the membrane in contact with aqueous solvent. The internal charge residues line the center of the helix bundle of each monomer as to form a hydrophilic channel that facilitates the passage of protons; similar structure to other membrane pumps and channels.
251
The primary photochemical process of photosynthesis in purple photosynthetic bacteria is mediated what?
mediated by the photosynthetic reaction center (PRC), a transmembrane (TM) protein, four other chromophores and a nonheme Fe(II) ion.
252
A transmembrane (TM) protein consists of what?
atleast three nonidentical ~300 residue subunits that collectively bind four chlorophyll molecules
253
The transmembrane portions of most TM proteins consist of what?
bundles of one to >20 helices, most of which are closely perpendicular to the membrane although some may be obliquely orientated and/or not fully transverse the membrane,
254
The outer membranes of gram negative bacteria contain what?
contain embedded channel-forming proteins called porins
255
The porins or gram negative bacteria are usually what?
trimers of identical 30- to 50- kD subunits that permit the passage of solutes of less than ~600D
256
porins are located where?
in outer membranes of gram negative bacteria as well as in eukaryotes's mitochondria membrane and chloroplast membranes.
257
what is an indicator that mitochondria and chloroplast come from bacteria?
They contain porin
258
Rhodobacter is an example of what?
porin
259
OmpF and PhoE is an example of what?
E. coli porin
260
porin forms what?
channels
261
Each monomer of the porin homotrimeric protein predominately consists of what?
16-stranded antiparallel Beta-barrel which forms a solvent-accessible pore
262
In the OmpF and phoE porin, the N- and C- termini associate how?
via a salt bridge in the 16th Beta-strand thereby forming a pseudocyclic structure.
263
the side chains of OmpF and phoE porin at the membrane-exposured surface are _____ forming what?
nonpolar forming a hydrophobic band encircling the trimer.
264
The side chains of OmpF and phoE porin atthe solvent-exposed surface of the protein, including the lining of walls for the aqueous channel are _____
polar
265
TM proteins are ____ proteins?
Integral proteins
266
Fatty acid amide hydrolase (FAAH) is what?
an enzyme that is an integral protein that binds to the cytoplasmic leaflet of the plasmic membrane.
267
How is FAAH like cytochrome b5?
monotopic; an integral protein that binds to cytoplasmic leaflet of the plasma membrane.
268
How does integral proteins structure differ from that of water soluble proteins.
Their organizations are opposite of each other
269
What is the structure of integral proteins?
Their membrane-exposed residues are more hydrophobic on average than their interior residues that have average hydrophobicities and packing densities comparable to those of water-soluble proteins.
270
For integral proteins What residues are at the C and N terminus?
hydrophilic segments (only a few) most of the outer region is still hydrophobic
271
Integral and water-soluble proteins are are both stabilized by what?
the exclusion of their interior residues from the surrounding solvent, although in the case of integral proteins the solvent is the lipid bilayer
272
What strengthens transmembrane proteins hydrogen bonds?
the low polarity and anhydrous environments
273
In TM proteins the portions of the transmembrane secondary structural elementary (helices in BR and PRC and beta strands in the porins) that contact the bilayer's hydrocarbon core consists mainly of?
nonpolar residues Ala, Ile, Leu, Val, Phe
274
In TM proteins the portions of the transmembrane secondary structural elementary (helices in BR and PRC and beta strands in the porins) that penetrate the bilayer's interface region, are enriched with?
Trp, and Tyr. Hence TM proteins's hydrophobic transmembrane bands are bordered by rings of Trp and Tyr side chains that delineate the water-bilayer interface.
275
The side chains of Tm proteins are orientated such that the polar portions (N and O atoms) extend _____ called? while ______ side chains located near the interface tend to be similar orientated.
extend into the polar region of the membrane called snorkeling; Lys and Arg located near the interface tend to be similar orientated.
276
Phe, Leu, and Ile side chains in TM proteins tend to do what?
point inward toward the membrane core called antisnorkeling.
277
G-Protein Coupled Receptors (GPCRs) are what?
very large superfamily of genes all encoding proteins containing 7 trans-membrane (7TM) helixes with little homology between family.
278
G-Protein Coupled Receptors (GPCRs) are unique in eukaryotes these receptors are the major sensors involved in _______
transducing stimuli from outside the cell to inside the cell.
279
ligands vary in size from ___ to ____
from very small olfactory molecules to multi-protein complexes
280
G-proteins are what type of species?
trimeric species consisting of three subunit: Galph, GBeta and Glambda
281
Galpha are _____ binding proteins that are what ?
GDP/GTP binding proteins are farnesylated at their C termini and thus associated with the intracellular membrane
282
These Galpha proteins possess intrinsic GTP-ase activity, and cycle between?
an inactive GDP-bound form and an active GTP- bound form.
283
Gbeta and G lambda are _____ species
dimeric
284
there are _____ different genes for distinct Gbeta?
7
285
There are ____ different genes for Glambda
12
286
Exocytosis
Release of vesicle contents outside of cell.
287
Endocytosis
Vesicles form around something outside cell,
| Bringing it inside cell.
288
Vesicles are coded with what?
proteins
289
post translationally translocated secretory proteins have signal sequences that are only _______
only mildly hydrophobic
290
where are secretory proteins synthezied?
cytoplasm atleast partially some cannot be translocated until after fully synthezied in the cytoplasm
291
co and post translation is mediated by
translocon which a passive pore but noes not have free energy that drives translocation
292
in cotranslation translocation is mediated by
ribosomially mediated extension of polypeptide
293
the rough RER contains ______ channels?
ion conducting channels
294
what happens to ion conducting channels when RER is treated with puromycin? what does this suggest?
increases; puromycin is an antibiotic that causes ribosome to prematurely release growinf polypeptides suggesting the channels are usually pluged by the presence of polypeptides.
295
the ion channels in RER are callled?
translocons
296
translocons are?
ion conducting channels that enclose aqueous pores that completely span the ER membrane
297
shortly after polypeptide synthesis is completed the partially processed proteins are transported to ______. where what happens?
golgi apparatus where further post-translational processing mostly glycosylation.
298
the Golgi stack has two faces which are
cis golgi network snc trans golgi network
299
the cis Golgi stack face is what?
is opposite ER and is port through which proteins enter the Golgi apparatus
300
The trans Gogi face is what?
processed proteins exit to final destination
301
anterograde transport
one form of transportation; cis to trans where cargo within membrane vesicles that bud off one compartment and fuse with another
302
cisterinal progression or maturation?
proteins carried as passenger of Golgi compartment that transit Golgi stack, cis eventually becomes tran cisternae. mediated by retorograde transport.
303
what are coated vesicles used for?
vehicle transport of proteins between RER, Golgi, and finalndestination
304
coated vesicles buds off _____ and fuses to ____
buds off from membrane of origin and later fuses to its target membrane.
305
carbohydrate moieties of TM glycoproteins and GPI anchors of GPI anchors of GPI linked proteins occur
only on external surface of plasma membrane
306
clathrin is an example of what?
coated vessicle
307
clathrin does wbat
transport TM, GPI linked and secreted proteins from the Golgi to plasma membrane.
308
COPI carries
retro and antertlgrade transport of proteins between Golgi compartments and returns escaped ER protein from Golgi to ER
309
COPII
transports from ER to Golgi
310
Clathrin shape?
polyhedral cage
