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ANAT 212 > Lecture 7 > Flashcards

Lecture 7 Flashcards

1
Q

name proteasome subunits

A

20s core
19s regulator - cap

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2
Q

describe 20s core of proteasome

A

2 outer rings of 7 similar alpha subunits - interact with gap
2 inner rings of 7 similar beta subunits
3 of beta subunits = have protease activity on inside surface - 6 proteins cut into aas
19s cap attaches to outer ring

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3
Q

describe 19s cap of proteasome

A

base with AAA-family ATPase subunits
protein unfoldase = unfolds to primary structure, line of aas goes into core
lid with nonatpase subunits = polyub receptors, dubs (cut and recycle ubs)
one up and one down

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4
Q

what is AAA

A

family of atp dependent proteins with many diff functions

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5
Q

describe ub receptor function

A

increase efficiency of targetting
select only k48 chains - lysines
recognizes poly ub if on lysine 48
protect adjacent premature DUB activity = reversible

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6
Q

name 2 types of ub receptors

A

intrinsic receptors
extrinsic receptors

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7
Q

describe intrinsic ub receptors

A

cap subunits = rpn10 and rpn13 bind poly ub

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8
Q

describe extrinsic ub receptors

A

shuttling ub receptors
separate from proteasome
bind poly ub through ub associated domain = UBA = proteasome must be close by, but not efficient so brings close to proteasome to be degraded
have ub like domain = UBL that is recognized by cap

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9
Q

describe proteasome cap = parts

A

ub receptor rpn13 and 10 = recognize tail and then attach to cap
base has AAA atpases = unfold and gets into core
unfoldase Rpt 1-6
lid
core
DUB rpn 8/11

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10
Q

describe cap functions - binding

A

lid ub receptors bind poly ub or ubl domains of shuttling receptors
dubs remove ub chains
base unfoldase passes substrate into core

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11
Q

describe proteasome core

A

cavity inside core
small and narrow
proteins have to stay unfolded
2 active subunits in each beta ring, 6 sites total with protease activity
one cuts at basic aa, one at acidic aa, one at hydrophobic aas
peptides diffused out and are digested into aas by peptidases = cuts into aas but if polypeptide = degraded by peptidases in cytosol

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12
Q

name step 1 of proteasome function

A

19s cap recognizes poly ub or ubl domain of shuttling receptor

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13
Q

name step 2 of proteasome function

A

dubs remove poly ub from substrate and pass it to base

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14
Q

name step 3 of proteasome function

A

base subunits use atpase activity to unfold substrate and feed it inside 20 s core

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15
Q

name step 4 of proteasome function

A

proteolytic beta subunits cleave substrate into short peptides or aas

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16
Q

describe ub proteasome summary - 8 steps

A

1 - Ub is activated by E1 and transferred to E2 on Cys side chains
2- E3 selects substrate polypeptide and transfers Ub from E2 to Lys side chains in the substrate
3- E2/E3 attaches more Ub onto Lys48 of the previous Ub, to make poly- Ub chain
4 - Poly-Ub is bound by shuttling receptor with UBL domain
5- 19s cap lid binds poly-Ub, or UBL domain of shuttling receptor
6- DUB removes poly-Ub
7 -19s base ATPase unfolds substrate
8 - Proteasome core cleaves at basic, acidic and hydrophobic sites

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17
Q

describe the cell - cytosol

A

soup
all reactions happen in cytosol - part pf cytoplasm

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18
Q

describe the cell - PM

A

allows cells to communicate to exterior and receive signals from interior
regulation of what gets in and out = vesicles and communications
proteins inserted in pm = not cytosolic proteins
Integrated into memebranes

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19
Q

describe the cell - secretory pathway

A

made in ER - proteins = transferred to golgi, modified and secreted to pm

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20
Q

describe the cell - endocytic pathway

A

take components form outside cell
vesicles fused by lysosome
isolated in cytosol by membranes = components

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21
Q

is a cell empty

A

hell NAH
very crowded
transport must be regulated or would be hard

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22
Q

describe secretory pathway

A

a transport system between several types of organelles and the cell surface (Plasma Membrane)
synthesis of proteins, lipids at the endoplasmic reticulum (ER)
traffic through Golgi, to the plasma membrane (PM)
internalization through endosomes, to degradation in lysosomes

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23
Q

are all organelles connected to secretory pathway

A

nooooo not all organelles
ex - mito

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24
Q

describe lumen

A

interior of secretory organelles = continuous with each other and extracellular space
vesicles bud from one organellar membrane and fuse with another without releasing contents into cytosol
lumenal environment (salts, ph, protein, cofactors) = similar to extracellular space (plasma) BUT DIFF from cytosol

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25
what is main diff between cytosol and lumen (extracellular)
cytosol = reducing environment, no disulfide cysteine bonds ER = oxidizing so losing electrons, disulfide bonds between cysteine here
26
name 4 important functions of biological membranes
provide enclosure to cells and to organelles within cells - like doors, regulate in and out allow regulated transport of materials between compartments provides sites within cells for biochemical reactions - can favour certain ones supports contacts with environment outside cells
27
describe important function of biological membranes - provide sites
Photosynthesis, oxidative phosphorylation metabolism of biological molecules = lipids, glycans, others
28
describe important function of biological membranes - supports contacts
cell motion, recognition of other cells, cell fusion = with exterior, like fibroblasts transmission of signals from exterior to interior of cells
29
describe properties of membranes
form hydrophobic barriers between aq compartments (hydrophilic) within cell - cytosol and organellar lumens flexible and can be formed into diff shapes
30
what are membranes selectively permeable to
small hydrophobic molecules not to charged/polar molecules and big hydrophobic
31
what controls the movement of impermeable molecules across membrane
specialized protein complexes control movement of impermeable molecules across membranes
32
how do membranes store energy
as concentration gradients - mainly happens in mitochondria voltage - nerve cells ph, potassium, sodium, calcium gradients
33
describe model of membranes
fluid mosaic model = membranes made of lipid molecules and membrane proteins lipids organized in bilayer = sheet that is polar on each side and hydrophobic in middle hydrophobicity acts as a barrier to water soluble molecules membrane proteins can rotate and diffuse laterally in fluid bilayer
34
can phospholipids flip
noooooo moves laterally or opens and closes
35
name major membrane lipids
phospholipids - in all membranes glycolipids = only at pm (not in er or golgi) cholesterol = preferentially located in pm other types with special functions
36
what do all membrane lipids have
hydrophobic sections - interior
37
what determines physical properties of membrane
lipid composition mobility = diffusion, rotation curvature, thickness
38
can lipids flip
YAAAA regulated by proteins lipid in membrane can flip from one layer to next but proteins in membrane CANNOT
39
describe phospholipids - abundance
most abundant lipids
40
name phospholipids parts
polar head groups 2 fatty acid tails
41
describe polar head groups of phospholipids
choline or other charged group phosphate and glycerol classification by head groups
42
describe fatty acid tails groups of phospholipids
Hydrophobic diff lengths saturated = no double bonds, all single covalent bonds unsaturated = 1 or more double bonds = forms kink in trail found in many diff combos with head groups
43
name phospholipid head groups
PC = phosphatidyl choline PE = phosphatidyl ethanolamine PS = phosphatidyl serine most common sphingomyelin = SM = not glycerol lipid but related
44
which phospholipid head group is not abundant
PI = phosphatidyl inositol can be phosphorylated and act as signalling molecules
45
what affects lipid mobility
head group size and charge
46
describe phosphatidyl ethanolamine
glycerol forms ester linkage with fatty acid tail = 3rd carbon binds phosphate and phosphate binds polar group
47
describe phosphatidyl serine
has neg charge usually faces cytosol
48
describe phosphatidyl choline
Attached to choline
49
describe sphingomyelin
has choline in polar head bit diff amide linkage to fatty acid tail
50
describe phosphatidyl-inositol
other type of lipid sugar oh can be phosphorylated regulatory molecule faces cytosol
51
describe fatty acid tails
2 of them hydrocarbon chain of 14-24 carbons varying number of double bonds Saturated tails = straighter and more flexible = if long = membrane thicker, determines which proteins will be integrated double bonds introduce bends in tail = reduce flexibility and length, has kink types of tails in membrane determine thickness and fluidity AMPHIPATHIC - polar head groups
52
describe unsaturated fatty acid tails
cis double bond = less flexible H's in same plane not as large kink so shorter increases fluidity of membrane
53
describe saturated fatty acid tails
longer
54
describe glycolipids
only found on outside surface of pm = always faces exterior of cell head groups contain diff sugar groups in many combos = important for cell contacts with environment and other cells sugar = glucose, galactose or nanosugar ceramide = also basis of SM (sphingomyelin) and the 3 sugars = galactosecerebroside, ganglioside, sialic acid
55
describe cholesterol
structurally diff from other lipids
56
why is cholesterol rigid
steroid ring structure lateral mobility, rotation much lower reduces mobility pf surrounding phospholipids, makes fatty acid tails more rigid
57
describe cholesterol structure
amphipathic hydrophobic fatty acid tail (hydrophobic interaction = straight so thicker) and polar head group integrated between lipids of membrane = provide rigidity, reduces lateral movements and rotations
58
describe membrane symmetry
many biological membranes are asymmetric = lipid composition on each side is diff asymmetry of pm is important for function exterior has glycolipids interior has stronger neg charge - high PS levels = transmits signals asymmetry is not absolute but actively maintained
59
describe inner and outer leaflet of membrane
outer = pc, sm, glycolipids inner = pe, ps, pc, low amount of pi (signalling) = molecules that transmit signals, has sugar and oh group = can be phosphorylated
60
describe organelle lipids
lipid composition is diff between organelles, depends on biological requirements other specialized lipids found in diff membranes
61
describe main components of PM, ER and mito
PM = highest cholesterol, and SM ER & mito = higher levels of PC and PE
62
what are microdomains
regions of membrane that are organized laterally = sideways, in patches - diff from rest of membrane
63
where are lipid rafts located
PM and trans-golgi = have special domains called lipid rafts
64
describe lipid rafts
thicker than surrounding membrane - rich in cholesterol lipids with longer tails cluster together in rafts
65
what does cholesterol do - lipid rafts
cholesterol binding straightens lipid tails, causing thicker membrane = many cholesterols so v thick = 12-14 carbons, fatty acid trails may get together to make lipid rafts diff protein content and biological function
66
describe why microdomains are important
some proteins that regulate communication of cell to exterior = only integrated in these microdomains = diff from other membrane parts bc how thick they are
67
what does glycerol do - fatty acids
link between polar head and 2 fatty acid tails

ANAT 212 (34 decks)

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