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Advanced Biology — Cell Signaling

Signal transduction pathways and cellular communication

S
second_messenger 25 terms Jan 22, 2026
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Terms 25

1
Signal Transduction
Process converting extracellular signal into intracellular response via molecular cascade
2
Ligand
Molecule binding to receptor; can be hydrophilic (surface receptors) or hydrophobic (intracellular receptors)
3
G Protein-Coupled Receptor (GPCR)
Seven-transmembrane receptor; activates G protein on binding ligand; largest receptor superfamily
4
G Protein
Heterotrimeric (Gα, Gβ, Gγ); GDP-bound=inactive; GTP-bound Gα=active; intrinsic GTPase
5
Adenylyl Cyclase
Enzyme producing cAMP from ATP; activated by Gαs; inhibited by Gαi
6
cAMP (Second Messenger)
Cyclic AMP activates PKA; downstream phosphorylation cascade; hydrolyzed by phosphodiesterase
7
Protein Kinase A (PKA)
Activated by cAMP; phosphorylates serine/threonine residues; activates transcription factors (CREB)
8
Phospholipase C (PLC)
Activated by Gαq; cleaves PIP₂ into IP₃ and DAG (second messengers)
9
IP₃ (Inositol Trisphosphate)
Second messenger releasing Ca²⁺ from ER; triggers PKC activation and other Ca²⁺-dependent events
10
DAG (Diacylglycerol)
Second messenger activating Protein Kinase C (PKC)
11
Receptor Tyrosine Kinase (RTK)
Receptor phosphorylates tyrosines on activation; dimerizes; e.g. EGF receptor, insulin receptor
12
RAS Pathway
RTK → Grb2/SOS → Ras-GTP → Raf → MEK → ERK; controls proliferation
13
PI3K/Akt Pathway
RTK → PI3K → PIP3 → Akt activation; promotes survival, growth, metabolism
14
JAK-STAT Pathway
Cytokine receptor → JAK kinase → STAT phosphorylation → nuclear translocation → gene expression
15
NF-κB Pathway
Inflammatory signaling; IKK phosphorylates IκB → NF-κB released → inflammatory gene expression
16
Wnt Pathway
Wnt → Frizzled → Dishevelled → inhibit destruction complex → β-catenin enters nucleus; development and cancer
17
Notch Pathway
Cell-to-cell contact; ligand cleaves Notch; NICD enters nucleus; controls differentiation
18
Hedgehog Pathway
Shh ligand → Ptch inhibition → Smoothened active → Gli transcription factors; development
19
TGF-β/Smad Pathway
TGF-β → Smad phosphorylation → nuclear translocation → controls proliferation, differentiation
20
Negative Feedback in Signaling
Active pathway inhibits upstream components; limits duration and magnitude of signal
21
Scaffold Proteins
Proteins organizing signaling molecules into complexes; improve speed, specificity, localization
22
Phosphatase
Enzyme removing phosphate groups; counters kinase activity; e.g. PP2A, PTEN
23
Ubiquitin-Proteasome System
Ubiquitin tags proteins for proteasomal degradation; regulates signaling protein levels
24
mTOR Pathway
Integrates nutrient, energy, and growth signals; controls protein synthesis, autophagy; two complexes
25
Apoptosis Signaling
Intrinsic (mitochondria, Bcl-2 family, cytochrome c) and extrinsic (death receptors, caspase-8) pathways