Cramming Flashcards
1
Q
What is the most common lipid in membranes?
A
Phosphoglycerides
2
Q
Describe phospholipids.
A
Amphipathic
Asymmetrical
3
Q
What is spontaneous aggregation dependent on?
A
Fatty acid length
Temperature
Degree of saturation
4
Q
What property of membranes does cholesterol enhance?
A
Fluidity
5
Q
What are liquid ordered regions resistant to?
A
Non-ionic detergents
6
Q
What are stored in lipid droplets?
A
Triglycerides and cholesterol esters
7
Q
What is phospholipase A2 an example of?
A
Peripheral protein
8
Q
How are lipid anchored proteins attached?
A
N-terminal glycine attached to fatty acyl group such as palmitate or myristate
9
Q
What is an example of an energy independent flippase?
A
ER Flippases
10
Q
What is an example of an energy dependent flippase?
A
Inward: P4 P-type ATPase
Outward: ABC transporters
11
Q
How are soluble proteins and membrane proteins transported?
A
Signal based
12
Q
How are integral proteins and plasma membrane proteins transported?
A
Vesicle based targeting
13
Q
Where is the signal sequence located?
A
N-terminal
14
Q
Describe ER signal sequences.
A
6-12 hydrophobic amino acids
16-30 residues long
One or more positive residues near the N-terminus
15
Q
Describe the SRP.
A
6 proteins bound by 300nt of RNA - P54 subunit of the SRP contains a hydrophobic cleft which binds to the hydrophobic amino acids of the signal sequence.
16
Q
What complex forms the mammalian translocon?
A
Sec61
17
Q
What could the signal peptidase recognise?
A
A, C, G, T and S (-1 and -3)
18
Q
What does Sec61/BiP do?
A
Prevents the polypeptide chain from slipping back into the cytosol.
BiP is a HSP protein that is located in the ER lumen - it contains a peptide binding domain and an ATPase domain that binds to and stabilises particularly or unfolded proteins.
Sec62 hydrolyses BiP.ATP causing a conformational change in BiP allowing it to bind to the polypeptide chain.
19
Q
Describe type I integral proteins.
A
Cleaved N-terminal sequence, luminal N-terminal and cytosolic C-terminal.
Stop-transfer anchor
20
Q
Describe type II integral proteins.
A
No cleavable N-terminus.
C-terminal luminal and N-terminal cytosolic
Signal anchor sequence
Positive charges on the N-terminal side
21
Q
Describe type III integral proteins.
A
Same orientation as type I but no cleavable N-terminal - positive charges lie on the cytoplasmic side (C-terminal side)
Positive-inside rule = positive charged residues present on the cytoplasmic side.
22
Q
Describe type IV.
A
Multiple transmembrane domains - mixture of stop-anchor and signal anchor sequences.
Can have either orientation.
23
Q
Describe type V.
A
Linked to an amphipathic phospholipid anchor embedded in the membrane - attached by covalent amphipathic molecule - GPI. Small sequence of amino acids near the N-terminus is recognised and cleaved off by a transamidase and linked to the pre-formed GPI membrane anchor.
24
Q
What is the sugar molecule in N-linked glycosylation attached to?
A
Nitrogen on an asparagine molecule
25
What are the two types of bonds that glycoproteins have?
Glycosidic - between the saccharides in the glycol
| Linkage between the glycan chain and the protein
26
What is the consensus sequence for linkage between the glycol and the protein?
Asn-X-Ser/Thr/Cys
| Asn can't be buried and must be on the luminal side of the ER.
27
What is the animal cell glycan usually used?
N-acetylglucosamine
Formation of dolichol-linked GlcNAc and then moves en bloc by oligosacchraide transferase to the protein
Dolichol = repeating isoprene units
2 GlcNAc, 3 glucose and 9 mannose
28
What does Ero1 do?
Brings the thiol groups to PDI
29
How many disulphide bonds are in hemagglutinin?
6
| Completed monomers are inserted into the membrane where they interact with two other monomers forming a stable trimer.
30
What rotates the bond in proline?
Peptidyl-propyl isomerases - rotation around the peptide-prolyl bonds
Go from cis to trans
31
Why is proline constrained?
Cyclic structure so stabilise the cis formation
32
What happens in O-linked glycosylation?
Sugar (CMP, UMP) binds to the hydroxyl of serine of threonine
33
What is proteolytic processing?
Formation of an inactive protein to an active one - pair of amino acids are recognised by specific endonucleases (RR, KR, KK, RK)
34
What does shedding do?
Generates soluble forms of membrane proteins which act mainly at cell surfaces - carried out by members of the ADAM family and cause proteolytic removal of the extracellular domains of many membrane proteins
35
What is lipidation?
Addition of hydrophobic molecules to a protein
36
What are the three types of lipid modification?
Palmitoylation
Myristylation
Prenylation
37
Describe palmitoylation.
Often near the C-terminus (Cys) - no consensus sequence but near transmembrane domain on cytoplasmic side.
Enhances hydrophobicity and has a role in membrane trafficking
S-palmitoyltransferases add it and palmitoylthioesterases remove.
Includes = insulin receptor, rhodopsin, Ras GTPases and Fyn kinase.
C16
38
Describe myristoylation.
Irreversible - very stable. C14
Myristic acid derived compound - covalently attached by an amide bond to the alpha amino group of glycine.
Consensus sequence - Met-Gly-X2-X3-X4-X5-
X2 - not charged, aromatic or proline
X5 - Cys, Thr, Ser, Ala, Gly and Asn
39
Describe prenylation.
Farnesyl (C15) - consensus sequence: -C-A-A-X
| Gernasyl (C20) CC or CXC
40
How are rab proteins transported?
Escorted by rab escort proteins that deliver crenelated rab to destination membrane by binding hydrophobic, insoluble phenyl groups and carrying rab through the cytoplasm.
Prenyl groups on two cysteines in the C-terminus
41
What soluble ER proteins have KDEL sequences?
BiP and PDI
42
Describe mitochondrial targeting sequences.
Amphipathic helix, 20-50 residues, Arg and Lys rich on one side with hydrophobic residues on the other.
Lacks negatively charged amino acids
43
How do mitochondrial proteins get into the mitochondria?
Recognised by tom20/22 which passes to the import pore Tom40 and then to Tim44 (inner membrane pore)
44
Do proteins targeted to the mitochondria fold in the mitochondria or before?
Fold in the matrix
45
What is the peroxisome signal sequence?
SKL (peroxisome targeting sequence 1)
| Binds to the soluble carrier Pex5 and is then passed to receptors pex14 in the membrane - imported in a folded state.
46
How are nuclear proteins imported?
In a folded state - 7 residue sequence rich in basic amino acids near the C-terminus.
47
Describe the NES.
Leucine rich and short (hydrophobic)
48
What transports proteins from the ER to the golgi?
COPII
49
What does glycosyl transferase do and where?
Housed in some golgi compartments and it can add certain modifications as the secretory proteins move through the golgi
50
What is dynamin?
Family of severing proteins that disconnect an endosome from the membrane
Uses GTP or ATP
51
What is clathrin?
A triskelion shaped scaffold protein composed of three heavy chain and three light chains
Polymerises around the cytoplasmic face of the invaginated membrane and acts as a reinforced mould - allows membrane vesicle to form without direct association with the membrane.
52
What are the adaptor complexes?
AP1 - TGN to endosome trafficking
AP2 - no real known function
AP3 - protein trafficking to lysosome and other related organelles
AP4 - less well characterised
Connect cargo proteins and lipids to clathrin at vesicle budding sites, as well as binding accessory proteins that regulate coat assembly/disassembly
53
What are the examples of post-endocytic trafficking?
```
Transferrin (recyling endosomes)
LDL receptor (endosomes/lysosomes)
EGFR (degradation) - signallong platforms in endosomes and degradation to switch off EGFR signalling
```
54
What is caveolin mediated internalisation?
Cholesterol binding protein caveolin and glycolipid rich domains of plasma membrane - cover one third of the plasma membrane area.
55
What are lipid rafts insoluble to?
Triton-X 100
56
What is macropinocytosis?
Rearrangment of the actin cytoskeleton - formation of ruffles which may fold back on themseveles and fuss at the base of the plasma membrane
57
What do the complexes go from in the mitochondrial electron transport chain?
Negative redox potential to more positive redox potential
58
What is the better electron donor?
More negative redox potential
59
What are the four complexes that make up the mitochondrial electron transport chain?
NADH Co-Q oxidoreductase
Succinate-Q reductase
Q-cytochrome c oxidoreductase
Cytochrome c oxidase
60
What do flavins carry?
Electrons and protons
61
Where are flavin mono nucleotides found?
Complex I
62
What are the three types of iron cluster and what do they carry?
Electrons
FeS
2Fe-2S
4Fe-4S
63
What are the iron sulfur clusters bound to in the polypeptide?
Cysteine
64
What can quinone carry?
Electrons and protons
65
What is the passage of electrons in complex 1?
FMN - 4Fe-4s - 4Fe-4s - 4Fe-4s - Q(H)2 - quinone pool
66
What is complex I inhibited by?
Amytal or rotenone
67
What does complex II not do?
Pump protons
68
What is the passage of electrons in complex 2?
FAD - 2Fe-2s - 4Fe-4s - 3Fe-4s - CoQ
69
What is the overall equation for complex III?
Succinate + FAD = Fumarate + FADH2
70
What are the redox groups in complex III?
FeS centres
Heme molecules
Only complex to have cytochrome b
71
What happens in complex three?
Electron transfer via the proton motive force
72
In complex IV how many protons are moved to the inter membrane space?
4
73
What is F1 composed of?
3 alpha (regulatory) and 3 beta (catalytic)
74
What connects F1 to F0?
Gamma
75
What does F0 comprise of?
Ring of hydrophobic residues that drives the rotation
76
What is the mechanism of ATP synthesis?
1) Translocation of protons carried out by F0
2) F1 catalyses formation of phosphoanhydride bond
3) Dissipation of proton gradient by F0 and F1
77
What is the P:O ratio for NADH?
10/3.7
78
What is the P:O ratio for FADH?
6/3.7
79
How many electrons does the education of one oxygen require?
2
80
How many molecules of ATP does 8 protons make?
3 (3.7H+/ATP)
81
What are the photosynthetic organisms?
Bacteria
Algae
Plants
82
What are the principal light harvesting molecules?
Chlorophylls
83
What is the structure of chlorophyll?
Cyclic tetrapyrolle - conjugated double bond system that are important in the excitation and transfer of electrons
84
What light does chlorophyll absorb?
Red and Blue
85
What is the difference between chlorophyll and heme?
Magnesium ion in chlorophyll
86
Where does charge separation occur?
Reaction centres
87
Describe bacteria rhodopseudomonas viridis?
Consists of four polypeptide chains - L, H, M and cytochrome
L and M are structural
Bacteriopheophytin is chlorophyll without the magnesium
88
What is the special pair in rhodopseudomonas viridis?
P960
Electrons move to bacteriopheophytin - then passed onto Qa at the same time as another electron is taken up by P960 from cytochrome c. Qa now transfers to Qb - and Qb picks up a hydrogen at the same time the cycle is repeated until QH2 is formed at Qb
89
What happens to the QH2 produced at Qb?
Goes to complex III of the respiratory chain and the cytochromes are re-reduced and 2 hydrogens are pumped into the periplasm - generates oxygen anaerobically in the presence of light
90
What is photosynthesis in plants often referred to as?
Z-scheme
91
What special pairs are in which photosystem?
```
PSII = 680
PSI = 700
```
92
What is the flow of electrons in the Z-scheme?
PSII - cytochome b6f - plasotcyanin - PSI
93
What is the overall net reaction for photosynthesis?
H20 + NADP = O2 + NADPH + 2H+
94
What does PSII contain?
The oxygen evolving complex - contains a manganese cluster and is present on the luminal side of the membrane.
95
What is the electron path of PSII?
Water is reduced to form oxygen
Electrons go to pheophytin
Then to QA (plastoquinone)
Then QB
96
What is PSII functionally equivalent to?
Bacterial reaction centre
97
What does each photon flight result in?
The abstraction of one electron from P680
98
What is reduced plastoquinone reduced by?
Cytochrome b6f - undergoes Q cycle
99
What is complex III homologous to?
Cytochrome b6f
100
Where does PSI sit?
The thylakoid membrane
101
What is the passage of electrons in PSII?
Chlorphyll - Quinone - 3 X 4Fe-4S clusters - ferredoxin
102
What happens in cyclic electron transport?
The electrons from the ferredoxin go back to the cytochrome b6f complex
103
When does cycle electron transport occur?
When ATP power is limiting but reducing power is plentiful
104
Where is the proton gradient across?
The thylakoid membrane - higher concentration In the lumen
105
What are carotenoids?
Absorb at 400-500nm and can transfer light to chlorphyll
| Isoprenoid compounds derived from geranylgernayl PP
106
What do carotenoids help to do?
Protect from oxidative damage
107
Where is chlorophyll a found?
Reaction centres and antenna complexes
108
Where is chlorophyll b found?
Only in antenna complexes
109
What are the accessory pigments in algae and cyanobacteria?
Phycobilisomes - absorbs yellow-green part of the spectrum
110
What is the structure of phycobilins?
Phycoerythrobilin linked via a cyst residue - lies on the surface of the thylakoid membrane
111
Where are PSI and ATP primarily found?
Unstacked regions
112
What happens when PSII > light than PSI?
Predominantly reduced PC - causes activation of LHCII kinase and unstacking of PSI so it can move away from PSII - phosphatase can reverse the process
113
What do PLD and PLA do?
Hydrolyse membrane bound phospholipases
114
What system secretes endocrine hormones?
Endocrine glands
115
What are the advantages of chemical messengers?
Spread to all tissues through the blood
Persist longer than electrical ones
Many different kinds of chemicals can act as hormones
116
What are the three major molecules that act as hormones in vertebrates?
Proteins and peptides - insulin and glucagon
Amines - catecholines
Steroids
117
What gland makes glucocorticoids and aldosterone?
Adrenal gland
118
What gland makes oestrogen and testosterone?
Gonads
119
What gland makes vitamin D?
Kidney
120
Are peptide hormones hydrophilic or phobic and what do they bind?
Hydrophilic
| Cell-Surface receptor
121
Are nuclear hormone receptors hydrophobic or hydrophilic and what do they bind to?
Hydrophobic
| Intracellular receptors
122
What are the steroid hormones?
```
Glucocorticoid
Mineralcorticoid
Androgens
Oestrogens
Progesterone
```
123
Describe adrenal hormones.
Small hydrophobic molecules
Derived from cholesterol
Synthesised in adrenal gland cortex
124
What is the adrenal gland divided into?
Capsule, Cortex and medulla
| Cortex into - glomerulosa, fasiculata and reticularis
125
What type of hormone is cortisol?
Glucocorticoid - synthesised in the fasiculata of the adrenal gland
126
What is cortisol involved in?
Stress, elevates blood pressure and sodium ion uptake
127
When is cortisol often taken?
Inflammatory disorder
128
What is aldosterone?
A principle mineralocorticoid
129
What is aldosterone produced from?
Progesterone in the glomerulosa of the adrenal gland
130
What effects does aldosterone have?
Raises blood pressure and fluid volume, increased sodium ion intake
131
Where is testosterone produced?
Leydig cells in the testis - transported to sertoli by androgen binding protein
132
What is testosterone converted to?
Dihydrotestosterone - more potent and promoter spermatogenesis
133
Where and how is oestrogen produced?
In the ovaries from testosterone by aromatase
134
What does oestrogen control?
Growth of uterus and mammary glands
135
What type of hormones are testosterone, progesterone, pregnenolene and oestrogen?
Gonadol steroid hormones
136
Describe progesterone.
Produced from pregnenolone and secreted from the corpus luteum. Responsible for changes associated with luteral phase of menstrual cycle, differentiation factor for mammary glands.
137
Describe pregnenolone.
Made directly from cholesterol, the precursor molecule for all C18/C19/C21 steroids. Not itself a hormone but critical for production of all others!
138
What are lipid soluble vitamins?
Vitamin D and Vitamin A
139
Where do the hormones produced by the hypothalamus travel to?
Pituitary gland - triggers a release of a corresponding hormone which travels to an endocrine gland and causes it to start producing a particular endocrine hormone.
140
What are examples of luteinizing hormones?
Progesterone/testosterone
141
What are examples of adrenocorticotropic hormones?
Cortisol
142
What are examples of follicle stimulating hormones?
Oestradiol
143
What are examples of angiotensin hormones?
Aldosterone
144
What are steroid hormones made from?
Cholesterol
145
What is the critical intermediate that cholesterol goes through?
Pregnenolene
146
What series of enzymes are responsible for the biosynthetic steps?
P450
147
What are cholesterol-derived hormones transported by?
Plasma carrier proteins
148
What are examples of plasma carrier proteins?
VitD binding protein
Sex-hormone binding globulin
Corticosteroid binding globulin
149
What is the purpose of carrier proteins?
Protect hormone in the blood and aid the transport of the hormone across the PM
150
What does the DNA binding domain of nuclear receptors contain?
Zinc fingers
151
What are nuclear receptors found complexed with?
Heat shock proteins
152
Describe the classical type I receptor.
Cytoplasmic or nuclear - associated with HSP in the absence of a ligand - bind as homodimers or inverted repeat DNA response elements
Includes PR, AR, GR and oestrogen receptors
153
Describe RXR type II receptors.
Nuclear
Not associated with HSP
Bind DNA in presence or absence of ligand
Bind as RXR dimers to direct repeat DNA response elements
154
What dissociated the HSP from the ligand binding domain?
Cortisol - when stressed.
| Allows binding to DNA.
155
What happens when the signal is no longer needed?
Hormone is no longer produced - circulating hormone is removed - dissociation from the receptor and receptor activation is no longer maintained.
156
What processes do hormones undergo in metabolism?
Hydroxylated, sulphated, glcosylated - more hydrophilic form and ready for excretion
157
What happens to thyroid hormones?
De-ionated
158
Where are the adrenal glands located?
Just above the kidney
159
What is the medulla stimulated by?
Sympathetic division of the autonomous nervous system
160
What is the cortex stimulated by?
Anterior pituitary, through ACTH
161
What part of the adrenal gland produces hormones?
Cortex
162
What do glucocorticosteroids (mainly cortisol) stimulate?
Gluconeogenesis - synthesis of glucose from non-hexose substrates
Mobilisation of amino acids from extra-hepatic tissues
Inhibition of glucose uptake in muscle and adipose tissue
Breakdown of fatty tissues
163
What does cortisol bind to?
The glucorticoid receptor in the cytosplasm - translocates to the nucleus
164
What is cortisol secreted in response to?
Adrenocorticotropic hormone from the anterior pituitary (under control of CRH) - CNS responsible for this
165
How is cortisol regulated?
Negative feedback - inhibits CRH
166
What disease is caused by excess cortisol?
Cushings
| Weight gain, excess sweating, bruised skin, suppression of immune response
167
What is the most common cause of cushings?
Corticosteroid medication and tumours
168
What is caused by hypoadrenocorticism?
Addison disease
| Slow developing and includes fatigue, muscle weakness etc.
169
What are the additional symptoms of Addisons disease?
Craving salty foods due to urinary loss of sodium, low blood pressure and skin darkening
170
What is often the cause of Addisons disease?
Infectious diseases or autoimmune destruction of the adrenal glands
171
What is caused by the loss of mineralcorticosteroids?
Elevation of potassium in extracellular fluid, urinary secretion of sodium, volume of extracellular fluid and blood decrease
Heart functions poorly
172
What does aldosterone target?
11 beta-hydroxysteroid dehydrogenase (cortisol to cortisone - weak affinity to MR)
173
What is the major target for aldosterone?
Distal tubule of the kidney - stimulates exchange of potassium and sodium
1) Increased resorption of sodium
2) Increased resorption of water
3) Increased renal excretion of potassium
174
What gene does aldosterone stimulate the transcription of?
Sodium-potassium ATPase
175
What does aldosterone have effects on?
Sweat glands, salivar glands and the colon
176
What is aldosteronism?
Conns syndrome
177
What effects does aldosteronism have?
Effects many cells in the body but focussed mainly on late distal tubules and collecting ducts of the kidney - increases activity of the sodium-potassium ATPase and increases sodium resorption and water retention - leads to volume expansion and elevated blood pressure and muscle wakens due to potassium changes
178
What is congenital adrenal hyperplasia?
Autosomal recessive diseases resulting - mutations in the genes encoding enzymes necessary for production of cortisol
179
What symptoms does congenital adrenal hyperplasia present?
Results in excess or deficient production of sex hormones and alters development of sex characteristics
Vomiting and salt wasting leading to death
180
What can be used to treat breast cancers?
Aromatase inhibitors
181
What is oestrogen response element?
ERE
182
What are the physiological outcomes of oestrogen?
```
Regulates stable body temperature
Primes body for milk production
Programmes uterus to nourish foetus
More HDL, less LDL
Increased NO production
```
183
How is oestrogen related to cancer?
Binding of oestrogen receptor to the ER stimulates proliferation of mammary cells - increase cell division and DNA replication
Oestrogen metabolism produces genotoxic waste
184
What does tamoxifen do?
Selective ER inhibitor - treats breast cancer and man boobs
185
What does vitamin D do?
Regulates levels of calcium, phosphorus and mineralisation of bone
186
What is the active form of vitamin D?
1,25-dihydroxycholcalciferol
| - metabolised in the liver and kidney
187
How does vitamin D work?
Increases expression of proteins that promote transport of calcium from the lumen of the intestine, across epithelial cells into blood
188
What receptor does vitamin D homo-dimerase with to activate transcription?
RXR
189
What disease does vitamin D deficiency cause?
Rickets
Osteomalacia in adults
Inadequate exposure to sunlight and decreased dietary intake of VitD
190
What does log℗ show?
How permeable small organic molecules are
| The higher the Log℗ the greater permeability
191
In facilitated transport how do molecules move?
Down their concentration gradient
192
What are the four main classes of transporters?
ATP powered pump
Ion channels
Transporters
Pores
193
What is OmpX?
Beta barrel that is an adhesion protein
194
What is found at the two bilayer interfaces?
Aromatic residues - aromatic belt or girdle
195
What is the typical structure of beta-barrels?
Homotrimers with 16 or 18 beta-strands
196
What has smaller pores out of OmpC and OmpF?
OmpC
197
What is PhoE selective for?
Phosphate
198
What is LamB?
Maltose porin and receptor for phage lambda
199
What is FepA and FhuA?
Uptake pores for siderophores, very specific. Active uptake as coupled to TonB
200
What is opening and closing of gap connexins controlled by?
Phosphorylation
201
What do monomers of gap junctions consist of?
4 transmembrane alpha helices
202
What are the four classes of ATP powered pumps?
F, V, P and ABC
203
What do F-class pumps do?
Synthesise ATP not hydrolyse
204
How do V class pumps work?
In reverse to F-class
205
Where are P-class pumps?
Fungi, plants and eukaryotes
206
What are the three domains of P-class pumps?
Transmembrane pump
ATPase domain
Phosphorylation site
207
Where are calcium P-class pumps?
Cardiomyocytes
208
What are the two states of calcium P class pumps?
```
E1 = high affinity for calcium
E2 = low affinity for calcium
```
209
For how many ATP molecules are 2 calcium ions transporter?
1
210
Where are ABC transporters found?
Animals, plants and microorganisms
211
What are the four domains of ABC transporters?
Transmembrane (2)
| Cytoplasmic (2)
212
What are examples of ABC transporters?
Maltose transport
CFTR
Vitamin B12 transporter
MDR1
213
Describe a vitamin B12.
BtuB is a specific beta barrel coupled to TonB
BtuF is a periplasmic binding protein
BtuCD is an ABC transporter
One BtuF is an ABC transporter
BtuC contains 10 transmembrane helices giving the vtuC2D2 more transmembrane helices than the standard ABC transporter
214
What does Mph1 transport?
Hydantoin
| Sodium coupled transporter
215
What does BETP transport?
Betaine-sodium symporter
| Member of betaine/choline/cartinine
216
What is XYLE?
Bacterial homologue of GLUT1
D-Xylose-proton symporter
4 alpha helices at the bottom of it which don't know what they transport
217
What does transporters curve look like?
Michaelis-menten
218
Where is GLUT1 found?
RBC and BBB
219
What is GLUT4 responsible for?
Insulin movement
220
What disease is associated with a mutation in GLUT1?
De novo disease
221
Where is GLUT4 present?
Muscles
222
Where do you want to actively take up glucose?
Intestine - SGLT1
| Kidney - SGLT2
223
What is the common architecture of potassium channels?
Four subunits
6 transmembrane helices (KscA only has 2)
The channel is lined by 1 transmembrane helix of each subunit
P-helix = fills the top of the cone structure
224
What is the selectivity filter in KscA?
Loop comprised of 6 amino acids
225
How many helices does each subunit have?
2
226
Where about in the transporter are potassium ions hydrated?
In the cavity - one potassium ion in there
227
How many potassium ions are there in the channel?
2
228
Why is the opening channel of sodium bigger than potassium?
Sodium may be transported in with water
229
What acts as a hinge in KscA?
Glycine residue
230
Where is Kv1.2 located?
Action potentials
231
In Kv1.2 what do helices 1-4 do?
Voltage sensing domain
232
In Kv1.2 what is helix 6 responsible for?
Opening and closing of the channel
233
How are Kv N-type inactivated?
Ball and chain mechanism - positive charges on the N-terminal domain bring the domain to the pore - intrinsically disordered and so enters the hydrophobic channel
234
What do TRP channels do?
Play a role in all five senses
235
How many trip genes are there?
27
236
What type of channels are trp?
Cation - calcium sensing
237
How many helices to trip channels have?
6 transmemebrane domains and assemble into tetramers
238
What are the sensory roles of trip?
Nociception, temperature reception and taste
239
What are the seven families of trip?
A, V, P, C, M, N, ML
240
What does TRPM5 contribute to?
Taste - bitter, sweet and urmani
241
What is TRPV1 involved in?
Hot
242
What is TRPM8 involved in?
Cool
243
What is TRPA1 involved in?
Pungent
244
Where are TRPV1 and TRPM8 expressed?
Nociceptors in doral root ganglions and trigeminal neurons
| Temperature sensors
245
Where is TRPA1 expressed?
Small-diameter nociceptors - temperature sensor
