Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

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

Lecture 14 - Signal Processing Pathways 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
Second messengers are
Intracellular signalling molecules released after the extracellular first messengers
26
Cytoplasmic cAMP is normally
Very low | But can increase rapidly
27
What enzyme converts cAMP to AMP (turns off the signal?)
Phosphodiesterases
28
cAMP causes effects through
Protein Kinase A (PKA)
29
Structure of PKA
2 catalytic subunits and 2 inhibitory subunits
30
When cAMP binds to PKA
The inhibitory subunits are released and PKA is activated
31
PKA is
Localised in the cell by AKAPs (A kinase anchoring proteins) | Provides rapid response to signals
32
AKAPs
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
33
PKA phosphorylates (2)
Two kinds of target proteins: Fast (phosphodiesterase switch) Slow (CREB (dna transcription))
34
Phosphorylated CREB (by PKA)
Controls transcription | Binds to CBP and CRE portions of DNA upstream of target genes
35
Trimeric Gq proteins activate
Phospholipase C-beta (membrane bound)
36
Phospholipase C-beta acts on
phosphatidylinositol 4,5-bisphosphate | PI(4,5)P2
37
PI(4,5)P2 is the
least abundant phosphoinositide in the PM
38
Phosphatidylinositol
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
PI(4,5)P2
Is cleaved to inositol 1,4,5- | triphosphate (IP3) and diacylglycerol (DAG)
40
Cleaved DAG
Remains at the plasma membrane and immediately binds Protein Kinase C (PKC)
41
IP3 binds
A gated Ca2+ ion channel in the ER membrane, causing an increase in Ca2+ concentration in cytosol
42
Ca2+ binds and activates
PKC, which phosphorylates specific target proteins
43
When a Ca2+ channel is transiently opened
Ca2+ rushes out
44
Propagation of a local Ca2+ signal
Results in waves or spikes
45
Ca2+ is used for
Egg activation Muscle cell contraction Neurotransmitter secretion
46
Ca2+ concentrations in the cytosol are
Low (10-7)
47
Low cytosolic Ca2+ is achieved by (3)
1. Ca2+ pump in ER membrane 2. Ca2+ importer in mitochondrial membrane 3. Ca2+ binding molecules in the cytosol
48
Ca2+ waves and spikes are controlled by
Positive and negative feedback | Released Ca2+ propagates further release until v high concs then inhibits
49
Ca2+ spikes are recognised by
CAM kinases
50
Calmodulin is a
Protein which changes conformation allosterically when bound to Ca2+ Needs 2 Ca2+ to bind Targets CAM kinases
51
The flexible structure of Ca2+ allows it to
Interact with many proteins, activating them
52
Calmodulin targets
CAM kinases
53
Ca2+ is a
Secondary messenger
54
Allosteric regulation is
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
CAM kinases can
Autophosphorylate | So even when Ca2+ is lost, the signal is active until phosphatases overwhelm it
56
Enzyme coupled receptors are usually
Transmembrane proteins that are directly or indirectly coupled to enzymes on the cytosolic side
57
Examples of enzyme coupled receptors
``` Receptor tyrosine kinases Tyrosine kinase-associated receptors Receptor Ser/Thr kinases Histidine kinase-associated receptors Receptor guanylyl cyclases Receptorlike tyrosine phosphatases ```
58
Receptor tyrosine kinases (RTKs) transmit
Signals from growth hormones and growth factors
59
When a ligand binds to a RTK it
Dimerises (joins with another) resulting in transautophosphorylation
60
Transautophosphorylation is
RTKs dimerising, phosphorylating and activating each other
61
What binds to the phophorylated RTKs?
Docking proteins
62
Docking proteins
Signal downstream
63
Different RTKs possess
Different docking domains | so will activate combinations of downstream targets
64
RTKs target
Small GTPases Ras and Rho AND PI 3-Kinase
65
Ras is anchored to
The cytoplasmic side of the PM
66
RTK docking proteins bind the
pTyr on the GTP receptors
67
Binding of the RTK docking proteins to Ras
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
Activation of a phosphatase and MAPK-dependent | inactivation of Raf regulates the
MAP cascade
69
MAP kinase cascade is also regulated by
Negative feedback
70
PI (RTK target) is the only lipid that can
Undergo reversible phosphorylation at multiple sites on its inositol head group
71
PI 3-kinase is able to produce
A variety of intermediates – all with a phosphorylated 3 | carbon
72
PI3 kinase diverts
Some of the PI(4,5)P2 from the PLC pathway, to generate PI(3,4,5)P3
73
PI(3,4,5)P3 interacts with
kinases: PDK1 and Akt
74
PDK1 phosphorylates and activates
Akt on two Ser/Thr residues
75
Akt targets
Proteins at the PM and elsewhere
76
Signalling pathways must
Co ordinate with each other to produce and appropriate cellular response
77
Downstream molecules from one pathway
Might act upon molecules from another
78
GPCRs and enzyme coupled receptors are the two main
Mechanisms that transduce information encoded in via an extracellular signal, into the cell
79
Second messengers are
Cyclic nucleotides, lipids and cations
80
Messages can be altered within the cell with
Intracellular regulation by upregulating, downregulating or integrating the signal with others
81
Signalling pathways work
Synergistically to produce the correct cellular response
82
Signalling steps (5)
1. Signal molecule 2. Signal receptor 3. Signal transduction cascade 4. Effector proteins 5. Altered cellular behaviour
83
Signalling can result in
Altered gene expression, metabolism, cell shape or movement

Advanced Cell Biology (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions