Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Advanced Cell Biology > Lecture 14 - Signal Processing Pathways > Flashcards

Lecture 14 - Signal Processing Pathways Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Signals are transduced by

A

Reversible signals causing conformational changes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Phosphorylation can

A

Switch on proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Phosphorylation is done by enzymes called

A

Kinases

Use ATP to phosphorylate at specific amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Dephosphorylation can

A

Switch off proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Dephosphorylation is done by enzymes called

A

Phosphatases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Phosphorylation occurs at

A

Serine and Threonine amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why does phosphorylation cause conformational change?

A

Negative phosphate gives amino acid a negative charge which causes a conformational change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Conformational change in a protein is what causes

A

Signalling

e.g. opens up the protein to interact with a substrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

GPCRs are

A

Serpentine receptors (spaghetti) with 7 TM domains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

GPCRs pick up

A

External signals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How many GPCRs in humans

A

700

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

When a ligand binds to a GCPR it causes

A

Conformational change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

GPCR

A

G protein coupled recptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

GPCRs act as GEFs (guanine nucleotide exchange factors) to

A

cause exchange of GDP to GTP on a set of 3 G proteins (heterotrimeric)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Heterotrimeric G proteins are

A

A set of three proteins, alpha, beta, gamma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Alpha and gamma subunits of G proteins are

A

Membrane bound by covalently attached lipid tails

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Alpha G protein subunits bind

A

GDP (inactive receptor) or GTP (active receptor)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

When alpha subunits are activated

A

They dissociate from the beta-gamma subunits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Steps of G protein activation (3)

A
  1. Signalling molecule binds to the GPCR
  2. Receptor causes alpha subunit to bind GTP
  3. Active alpha subunit then binds a target and activates it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

G proteins are inefficient

A

GTPases

Hydrolyse GTP, dissociate from target and bind with beta and gamma units again

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Many GCPRs are coupled to

A

Stimulatory trimeric G proteins Gs

adenylyl cyclase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Stimulatory trimeric G proteins Gs activate

A

Adenylyl cyclase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Adenylyl cyclase is a

A

Membrane bound enzyme

Produces cAMP from ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

cAMP

A

Is a second messenger
A derivative of ATP and used for intracellular signal transduction in many different organisms in the cAMP-dependent pathway

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Second messengers are

A

Intracellular signalling molecules released after the extracellular first messengers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Cytoplasmic cAMP is normally

A

Very low

But can increase rapidly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What enzyme converts cAMP to AMP (turns off the signal?)

A

Phosphodiesterases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

cAMP causes effects through

A

Protein Kinase A (PKA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Structure of PKA

A

2 catalytic subunits and 2 inhibitory subunits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

When cAMP binds to PKA

A

The inhibitory subunits are released and PKA is activated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

PKA is

A

Localised in the cell by AKAPs (A kinase anchoring proteins)

Provides rapid response to signals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

AKAPs

A

A kinase anchoring proteins
A group of proteins which bind the regulatory subunit of protein kinase A (PKA) and confine the holoenzyme to discrete locations within the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

PKA phosphorylates (2)

A

Two kinds of target proteins:
Fast (phosphodiesterase switch)
Slow (CREB (dna transcription))

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Phosphorylated CREB (by PKA)

A

Controls transcription

Binds to CBP and CRE portions of DNA upstream of target genes

35
Q

Trimeric Gq proteins activate

A

Phospholipase C-beta (membrane bound)

36
Q

Phospholipase C-beta acts on

A

phosphatidylinositol 4,5-bisphosphate

PI(4,5)P2

37
Q

PI(4,5)P2 is the

A

least abundant phosphoinositide in the PM

38
Q

Phosphatidylinositol

A

A family of lipids that form a minor component on the cytosolic side of eukaryotic cell membranes
The phosphate group gives the molecules a negative charge at physiological pH

39
Q

PI(4,5)P2

A

Is cleaved to inositol 1,4,5-

triphosphate (IP3) and diacylglycerol (DAG)

40
Q

Cleaved DAG

A

Remains at the plasma membrane and immediately binds Protein Kinase C (PKC)

41
Q

IP3 binds

A

A gated Ca2+ ion channel in the ER membrane, causing an increase in Ca2+ concentration in cytosol

42
Q

Ca2+ binds and activates

A

PKC, which phosphorylates specific target proteins

43
Q

When a Ca2+ channel is transiently opened

A

Ca2+ rushes out

44
Q

Propagation of a local Ca2+ signal

A

Results in waves or spikes

45
Q

Ca2+ is used for

A

Egg activation
Muscle cell contraction
Neurotransmitter secretion

46
Q

Ca2+ concentrations in the cytosol are

A

Low (10-7)

47
Q

Low cytosolic Ca2+ is achieved by (3)

A
  1. Ca2+ pump in ER membrane
  2. Ca2+ importer in mitochondrial membrane
  3. Ca2+ binding molecules in the cytosol
48
Q

Ca2+ waves and spikes are controlled by

A

Positive and negative feedback

Released Ca2+ propagates further release until v high concs then inhibits

49
Q

Ca2+ spikes are recognised by

A

CAM kinases

50
Q

Calmodulin is a

A

Protein which changes conformation allosterically when bound to Ca2+
Needs 2 Ca2+ to bind
Targets CAM kinases

51
Q

The flexible structure of Ca2+ allows it to

A

Interact with many proteins, activating them

52
Q

Calmodulin targets

A

CAM kinases

53
Q

Ca2+ is a

A

Secondary messenger

54
Q

Allosteric regulation is

A

The regulation of a protein by binding an effector molecule at a site other than the enzyme’s active site The site to which the effector binds is termed the allosteric site
Calmodulin and Haemoglobin

55
Q

CAM kinases can

A

Autophosphorylate

So even when Ca2+ is lost, the signal is active until phosphatases overwhelm it

56
Q

Enzyme coupled receptors are usually

A

Transmembrane proteins that are directly or indirectly coupled to enzymes on the cytosolic side

57
Q

Examples of enzyme coupled receptors

A 
Receptor tyrosine kinases
Tyrosine kinase-associated receptors
Receptor Ser/Thr kinases
Histidine kinase-associated receptors
Receptor guanylyl cyclases
Receptorlike tyrosine phosphatases
58
Q

Receptor tyrosine kinases (RTKs) transmit

A

Signals from growth hormones and growth factors

59
Q

When a ligand binds to a RTK it

A

Dimerises (joins with another) resulting in transautophosphorylation

60
Q

Transautophosphorylation is

A

RTKs dimerising, phosphorylating and activating each other

61
Q

What binds to the phophorylated RTKs?

A

Docking proteins

62
Q

Docking proteins

A

Signal downstream

63
Q

Different RTKs possess

A

Different docking domains

so will activate combinations of downstream targets

64
Q

RTKs target

A

Small GTPases Ras and Rho AND PI 3-Kinase

65
Q

Ras is anchored to

A

The cytoplasmic side of the PM

66
Q

RTK docking proteins bind the

A

pTyr on the GTP receptors

67
Q

Binding of the RTK docking proteins to Ras

A

Brings a Ras-GEF to the PM which activates Ras
Ras activates a kinase
Causes a MAP kinase cascade
Results in phosphorylation of many target proteins
Cellular response

68
Q

Activation of a phosphatase and MAPK-dependent

inactivation of Raf regulates the

A

MAP cascade

69
Q

MAP kinase cascade is also regulated by

A

Negative feedback

70
Q

PI (RTK target) is the only lipid that can

A

Undergo reversible phosphorylation at multiple sites on its inositol head group

71
Q

PI 3-kinase is able to produce

A

A variety of intermediates – all with a phosphorylated 3

carbon

72
Q

PI3 kinase diverts

A

Some of the PI(4,5)P2 from the PLC pathway, to generate PI(3,4,5)P3

73
Q

PI(3,4,5)P3 interacts with

A

kinases: PDK1 and Akt

74
Q

PDK1 phosphorylates and activates

A

Akt on two Ser/Thr residues

75
Q

Akt targets

A

Proteins at the PM and elsewhere

76
Q

Signalling pathways must

A

Co ordinate with each other to produce and appropriate cellular response

77
Q

Downstream molecules from one pathway

A

Might act upon molecules from another

78
Q

GPCRs and enzyme coupled receptors are the two main

A

Mechanisms that transduce information encoded in via an extracellular signal, into the cell

79
Q

Second messengers are

A

Cyclic nucleotides, lipids and cations

80
Q

Messages can be altered within the cell with

A

Intracellular regulation by upregulating, downregulating or integrating the signal with others

81
Q

Signalling pathways work

A

Synergistically to produce the correct cellular response

82
Q

Signalling steps (5)

A
  1. Signal molecule
  2. Signal receptor
  3. Signal transduction cascade
  4. Effector proteins
  5. Altered cellular behaviour
83
Q

Signalling can result in

A

Altered gene expression, metabolism, cell shape or movement

Advanced Cell Biology (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions