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Advanced Cells > lec 8-9 cell compartments and communication > Flashcards

lec 8-9 cell compartments and communication Flashcards

1
Q

importance of compartments

A

provide local environments for specific metabolic functions

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2
Q

phosphoglycerides

A

2 long chain fatty acids

one unsaturated CC bond causing kink

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3
Q

amphiphilic molecules

A

polar and non-polar molecules in phospholipid bilayers

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4
Q

different phospholipid head groups…

A

determine properties

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5
Q

longer hydrocarbon chains..

A

stronger interactions

less fluidity

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6
Q

decreased temperature of phospholipid bilayers…

A

tighter packing

crystal formation

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7
Q

cholesterol

A

sits in gaps caused by kinks in chain
form steroid rings
regulate fluidity

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8
Q

effect of cholesterol on membrane

A

partly immobilises hydrocarbon chains

decreases mobility and permeability of the membrane

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9
Q

formation of compartments

A

sheets of bilayers form enclosed compartments
hydrocarbon tails avoid water
energetically favourable

lipid rafts - bring proteins together to interact with each other - caused by addition of cholesterol

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10
Q

phospholipid translocators

A

membrane-bound enzymes

catalyse ‘flip-flop’ of individual phospholipids across sides of bilayer

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11
Q

3 mechanisms of protein movement between compartments

A

gated channels
translocators
vesicles

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12
Q

translocators

A

directly unwind and pull proteins across membrane from cytosol

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13
Q

vesicles

A

load and off-load cargo to different compartments via membrane fusion

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14
Q

NPC

A

nuclear pore complex

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15
Q

5 subunits of NPC

A 
annular
lumenal
ring
fibrils
nuclear basket
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16
Q

function of NPC

A

helps transport large molecules between nucleus and cytoplasm

barrier between nucleus and cytoplasm preventing harm to nuclear genetic material

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17
Q

nuclear localisation signals

A

positively charged amino acid sequence

tag proteins for import into cell nucleus

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18
Q

how are nuclear localisaton signals recognised

A

by nuclear import receptors directly or indirectly

using adaptor proteins karyopherins/importins

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19
Q

Ran

A

small GTPase protein - molecular switch

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20
Q

how is Ran switched off

A

GTPase activating proteins (GAPs)

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21
Q

Ran.GDP

A

lots found in cytosol
do not bind to Karyopherins
free for import of cargo

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22
Q

when do karyopherins cross the nuclear pore complex

A

when Ran.GDP is bound to cargo

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23
Q

what happens when Ran.GDP binds to cargo

A

karyopherins cross NPC
cargo is exchanged for Ran.GTP
Ran.GTP-karyopherin complex is transported back out to cytosol

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24
Q

2 active spaces in mitochondria

A

matrix

inter-membrane space

25
Q

Chaperone proteins

A

bind to synthesised proteins and prevent folding

hold them as polypeptides

26
Q

what do signal sequences form before they bind to protein translocator complexes

A

ampiphilic alpha-helices with +ve charged clusters on one side

27
Q

protein translocator complexes

A

TOM - transporter out of mitochondrial membrane

TIM - transporter into mitochondrial membrane

28
Q

TOM complex

A

binds to signal sequence
facilitates transport across outer membrane using ATP hydrolysis
chaperones dissociate

29
Q

TIM complex

A

sequence binds after interaction with TOM complex

30
Q

what drives initial translocation of +vely charged residues to the mitochondrial matrix

A

the mitochondrial membrane potential

31
Q

once the sequence has bound to TIM complex

A

translocation of +vely charged residues to mitochondrial matrix

ATP hydrolysis releases Hsp70 from polypeptide and drives the rest of the import

Hsp60 folds proteins correctly

32
Q

inter membrane proteins have hydrophobic region…

A

stops TIM from translocating protein through inter-membrane space

33
Q

inter-membrane proteins have second signal sequence..

A

transports back from matrix to inter-membrane space via OXA translocator

34
Q

transport into chloroplasts

A

GTP and ATP used to get photo stem proteins across the double membrane
H+ gradient used for crossing thylakoid membrane

35
Q

why is transport into endoplasmic reticulum different

A

it is a co-translational mechanism

the others are all post-translational

36
Q

signal recognition particle

A

N-terminal amino acid sequence recognises and targets specific proteins to the ER

composed of many proteins and RNA
large hydrophobic pocket - methionine

37
Q

using microbiology to study protein translocation

A

identify sequence to target specific protein
fuse sequence to reporter gene e..g GFP
express it in cells
mutageneiss alters single amino acids to determine which structural elements are important

38
Q

using biochemistry to study protein translocation

A

in vitro translated protein (labelled with radioactivity) is incubated with and without organelles

39
Q

why is cell communication necessary

A

cell organisation
control output signals
interpreting input signals

40
Q

examples of signalling molecules

A 
nucleotides 
small molecules 
steroids
proteins
fatty acids
dissolved gases
41
Q

examples of nucleotide signalling molecules

A

cAMP

NADPH

42
Q

nitric oxide on smooth muscle

A

relaxes smooth muscle
increased blood flow
erection

43
Q

paracrine secretion signalling

A 
molecule released into extracellular environment
acts locally on neighbouring cells
signal molecule rapidly taken up 
specific reaction initiated
signal doesnt diffuse far
44
Q

synaptic signalling

A

secretion of chemical into synaptic space as a result of electrical impulse
very rapid and specific signal
high conc. of hormone - low affinity of receptor for binding

45
Q

synapse-synapse

A

short range

46
Q

axons

A

long range signalling

47
Q

endocrine signallign

A

long range signalling
anywhere in body
hormone released into bloodstream
low conc of hormone in blood - binds with high specificity/affinity to receptor

48
Q

gap junction signalling

A

direct communication
allow transfer or small molecules and inorganic ions
cytoplasmic filled channels connecting cells

49
Q

indirect signal communication into a cell

A

signal binds to cell surface receptor inducing conformational change

50
Q

ion channel coupled receptors

A

rapid synaptic signalling
voltage gated channels undergo conformation change upon ligand binding
removes charged residues from channel allowing ion influx

51
Q

GPCR

A

7 transmembrane domains on receptors
ligand binds and conformational change to trimeric G proteins
1 subunit dissociates and activates enzyme

52
Q

enzyme couple receptors

A

1 transmembrane domain - forms a dimer
activates catalytic domain
tyrosine receptors
autophosphorylation of cytosolic sites on receptor - triggers other pathway 0 creates docking sites downstream

53
Q

where does phosphorylation mostly occur

A

serine and threonine residues of amino acids

54
Q

signals can be amplified

A 
one molecule activates one receptor 
cascade initiated
kinase activity
amplifies signal
effector proteins activated
55
Q

positive feedback mecahnisms

A

out put stimulates its own production

56
Q

signal speed depends on..

A

how the cell receives the signal

57
Q

examples of how fast signal speed is created

A

binding of neurotransmitter ion channel
phosphorylation of a protein
protein present in cell already - secretion

58
Q

examples of how slow signal speed is created

A

when gene expression is involved

e.g. cell growth, differentiation

Advanced Cells (10 decks)

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