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phgy 170 > Module 4 > Flashcards

Module 4 Flashcards

1
Q

Extracellular communication

A

signal is received from the outside of the cell

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2
Q

intracellular communication

A

( cell will collect info, synthesize the info and make decision) external communication will cause internal changes

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3
Q

direct cell to cell communication can be described as

A

Gap junctions

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4
Q

what are gap junctions?

A

made up of connexons that dock together to form channels from one cell to another, chemicals can move directly between cells

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5
Q

what can pass through gap junctions ?

A

small particles such as ions and signalling molecules - they are highly regulated and can open the door when needed ( thought to be a self defence mechanism )

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6
Q

how do cells communicate with each other when they arent touching ?

A

they will communicate through secretions where there are 4 types of secretions that can be distinguished by the type of cell or the location of the cell recieving the signal

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7
Q

autocrine secretions

A

released by a cell and have the same effects on a cell

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8
Q

paracrine secretions

A

released by cell and have effect on nearby cells

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9
Q

endocrine secretions

A

released by cell and will have effect on distant cell

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10
Q

neurotransmitters

A

released by the nerve terminal into the synapse

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11
Q

what is a lysosome?

A

organelles that break down misfolded and damaged organelles, nucleic acids, lipids etc

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12
Q

what is proteosomes ?

A

protein complexes that break down dmaged and misfolded proteins in the nucleus and cytosol

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13
Q

what are peroxisomes

A

take care of dangerous free radicals including ROCS, ALSO involved in the decomposing long chains of fatty acids, and cargo like uric acid

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14
Q

How will cargo get to the lysosome ?

A

-misfolded proteins and cellular content will tagged for the lysosome
-cargo is delivered to the lysosome via the endomembrane system
-M6P sugar tag on the cargo will send it to the lysosome along with proteases( same sugar tag)
-Vesicles will fuse with the lysosome where its contents will be emptied and digested by the proteases

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15
Q

What do lysosomes contain ?

A

high concentrations of proteases which are capable of cleaving membrane proteins and proteins in the lysosome
- also contain enzymes that are able to digest sugars and fats and can engulf damaged organelles –> will break down large molecules into basic parts that will be recylced back to the cytosol to be reused

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16
Q

what happens to the cytosolic proteins in the proteasome ?

A

will be tagged with a polyubiquitin chain which has multiple molecules of ubiquitin which is needed for the proteosome to recognize and degrade the proteins

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17
Q

explain nuclear proteins with proteasomes?

A

proteasomes can also be found in the nucleus which allows them to degrade nuclear proteins ( not export to cytosol )

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18
Q

describe peroxisomes

A

small organelles which contain enzymes that catalyze reactions . Specifically they are the place where Reactive oxygen species can be dealt with safely

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19
Q

what are the proteins in the peroxisomes called ?

A

peroxins which are synthesized in the cytosol and use targeting signals( PTS) to make there way to the peroxisome

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20
Q

what is apoptosis ?

A

known as programmed cell death, where it is used as form of protection for the body against cells that no longer function properly

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21
Q

what are the 4 steps in apoptosis ?

A
  1. initiation
  2. membrane blebbing and enzyme activation
  3. cell structure changes
  4. engulfment
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22
Q

how is apoptosis initiated ?

A

can be started from both intrinsic and extrinsic pathways,

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23
Q

intrinsic pathway of apoptosis ?

A

starts from outer membrane of mitochondria, and the pathway will get activated when there is severe DNA damage or ROS or toxins or trauma

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24
Q

extrinsic pathway in apoptosis ?

A

starts from external signals , begins at the plasma membrane receptor known as the death receptor in which neighbouring cells will release death ligands that will bind to receptor and start process

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25
Q

what is membrane blebbing ? and which enzymes are activated ?

A

when the cell begins to form protrusions or shrinks and is the first sign of apoptosis . Caspases enzymes are activated by both pathways and will cleave and activate more caspases called executioner capsases

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26
Q

what are the structural changes seen in the cell ?

A

executioner caspases will cause DNA to become fragmented and nuclear membrane will break down , the cytoskeleton will disassemble and the phospholipid content in the plasma membrane changes , organelles will persist and will be enclosed in apoptotic bodies

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27
Q

what happens in engulfment ?

A

phagocytes will endocytose the apoptotic bodies to dispose of them which are then safely digested by lysosomes of the phagocytes creating minimal disturbance in the cell

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28
Q

what is necrosis and when does it happen?

A

takes place from cellular injury in which the cell will try and repair itself - it is the pathway of cell death when a cell is beyond repair and the organelles dont function so the cell dies

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29
Q

what are the 3 steps in necrosis ?

A

Damage , swelling and destruction

30
Q

how is damaged caused

A

toxins, extreme heat or radiation, freezing, ischemia , pathogens mechanical trauma

31
Q

what happens in swelling ?

A

the organelles will lose there structure and start to swell where vacuoles will form and DNA may also be degraded depending on the damage

32
Q

what happens in destruction ?

A

structural integrity will be lost and the contents of the cell spill out because of small holes causing inflammatory signals
Proteins of the mitochondria will be released and exposure of lysosomal contents where nearby cells will also get damaged

33
Q

what are the steps in the protein kinase signalling cascade

A

1) Fibroblast growth factors (FGFs) can stimulate cell growth and will bind to FGF receptors ( FGFR)
2)binding will cause subunits to dimerize ,FGFR will undergo tryosine transautophosphorylation , to create phosphotyrosines on the cytoplasmic side which will be able to bind to different proteins
3)phosphotryosine can bind to Grb2 an adapter protein which will create a conformational change and allow it to bind to SoS, causing its activation an allow SoS to bind to Ras
4) Binding of SoS to Ras will replace GDP with GTP causing Ras to activate allowing it to bind to serine kinase known as Raf
5) Activated Raf will phosphorylate protein kinase MEK which will phospohorylate serine/ threonine kinase ERK allowing it to phospohorylate proteins in the cytosol and neucleus

34
Q

what are the steps in phospholipid kinase signalling cascade

A

1) Ligand binds to GPCR letting the receptor to interact with heterotrimeric G protein - this will stimulate the replacement of GDP for GTP in G alpha subunit allowing the heterotrimeric protein G protein disassociate from the receptor from receptor and leave Beta Y subunit and activated Ga- GTP
2)Ga- GTP will bind to the phospholipid kinase signalling protein (phospholipidase C , PLC) which will break down PIP2 to release second messengers, DAG and IP3
3) IP3 will diffuse freely in cytosol and activate its receptor and activate its receptor on the ER opening ligand gated CA+ channel where Ca+ will act as a second messenger actviating calcium binding proteins

35
Q

What is another name for signals ?

A

Ligands, which come from extracellular space and needs to bind to a receptor known as a signal tiggering molecule which will bind to site on target protein

36
Q

what are the 3 kinds of ligands ?

A

membrane impermeable. membrane permeable and physical receptors

37
Q

membrane impermerable ligands

A

most signals, which must bind to receptors on cell surface because they cannot penetrate membrane

38
Q

membrane permeable ligands

A

mainly steroids, can penetrate the membrane and are not limited to membrane receptors as they can bind with cytosolic receptors as well

39
Q

physical signals

A

include pressure temperature and light

40
Q

what are the 6 classes of receptors ?

A

G protein coupled receptors, guanylate cyclase , protein kinase receptors , transmembrane scaffolds , nuclear receptors ion channels

41
Q

GPCR structure

A

contains 7 transmembrane domains (h1-h7) and a Heteromeric G protein that with Alpha ,Beta and Gamma subunits

42
Q

GPCR function

A

binding of GPCR to receptor will cause a conformational shape change in the receptor leading to the activation of the G protein subunits

43
Q

Ion channel receptors functions

A

AKA, ligand gated channels , transmit signal information by permitting ions to flow through from one side to the other –> when specific ligand binds the channel will go through conformational change that opens the pores , do not use enzymes

44
Q

ion channels are responsible for

A

voluntary muscle contraction and is used for nerve cell communication

45
Q

guanylate cyclase

A

found as being bound to the membrane and in soluable form in cytosol

46
Q

structure of guanylate cyclase

A

has externalized ligand domain, transmembrane domain and and internal catalytic domain

47
Q

what is soluable guanylate cyclase used for ?

A

target for some membrane soluable ligands

48
Q

function of guanylate cyclase ?

A

when activated , catalytic domain of membrane bound version will GTP into cGMP which will bind to signalling proteins to initiate cell processes

49
Q

generally speaking the role of protein kinases is to do what?

A

phosphorylate other proteins that contain serine , theorine and tyrosine residues

50
Q

what are the 2 classes of protein kinases that act as receptors

A

Receptor Tyrosine kinases and serine/ Theorine kinases receptors–> will phosphorylate either tyrosine or Theorine

51
Q

tyrosine kinase receptor bind to ligand cascade of events

A

1) before binding the inactive receptors are separate polypeptides with inactive tyrosine kinase domains
2) Binding to signalling molecule will cause dimerization – activating the kinase
3) Transautophosphorylation happens when cytoplasmic tail of one subunit is brought close to tyrosine kinase domain of other subunit and opposite domain is phosphorylated
4) resulted phosphotyrosine amino acids are binding sites for signalling proteins to pass signal down the pathway
5) ligand is released and amino acid is dephosphorlayed by phosphoprotein where the kinase will reset to inactive state

52
Q

parts of a signal transduction pathway

A

1) either membrane permeable or impermeable receptors
2) signalling proteins and second messengers
3) cytoplasmic receptors
4) sometimes nucleus effectors

53
Q

2 kinds of protein kinase receptors

A

1) receptor tyrosine kinases ( RTK)
2) serine/theorine receptor kinases

54
Q

transmembrane scaffolds

A

dont always have specific function and will form in large clusters of receptors and signalling proteins

55
Q

function of transmembrane scaffolds

A

bring singalling proteins together
regulate signal transduction
send signal proteins to specific cellular area
isolate signalling pathways

56
Q

nuclear receptors

A

intracellular receptor that is found in the cytosol of the cell , bund to receptor , ligand such as steroids will move into the nucleus and can bind to steriod response elements that are able to control gene expression

57
Q

2 common features of all signalling proteins

A

mobility and catalysis( amplication of signals )

58
Q

purpose of signalling proteins

A

to transmit and amplify signals , can mobilize secondary messengers

59
Q

what are G proteins ?

A

proteins that bind GTP and propogate signals there are 2 kinds, monomeric and heterotrimeric which differ in the # of polypeptides

60
Q

4 steps in activated G protein

A

binding , seperation, propogation and cleave and reform

61
Q

binding stage of activation of G protein

A

heterotrimer containing subunits of beta nd gamma are bouND to GDP which is inactive - ligand binds to receptor will change form to interact with heterotrimeric G protein

62
Q

seperation phase and activation of G protein

A

exchance of GDP for GTP on the alpha subunit and heterotrimer will seperate in to 3 subunits , G proteins are active

63
Q

propogation phase in G protein activation

A

alpha, beta , gamma subunits will bind downstream targets to propogate signal pathway

64
Q

cleave and reform

A

Alpha subunit cleave GTP to form GDP which allow the subunits to bind to the hetertrimer again and will bring the protein back into its inactive form

65
Q

cytosolic protein kinases

A

can act as intermediaries that can activate other protein kinases and signalling proteins or can phospohorylate effector proteins directly

66
Q

calcium binding proteins

A

can cause downstream effects on other proteins ex) calmodulin , Ca levels high, will bind to calmodulin which will activate it causing a conformational change and will bind to its target

67
Q

adyenyl cyclase

A

a signalling protein that can bind to the alpha subunit on. hetertrimeric G protein

68
Q

2 different forms of alpha subunits on Heterotrimeic G protein

A

as- stimulate adenylyl cyclase where as Ai WILL inhibit it

69
Q

lipid kinases

A

signalling protein that will phosphorylate phospholipids in cytoplasmic leaflet - add phosphate group to polar head of phospholipid- also causes conformational change allowing it to bind to target to pass signal

70
Q

adaptor protein

A

not a receptor or enzyme , recognize phosphoylated amino acids and can form the glue for signalling networks - so cascades are associated in the right place at the right time

phgy 170 (4 decks)

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