L18: Intracellular Communciation And Signal Transduction Flashcards
1
Q
What is signal transduction
A
Sense the presence of biological signal
2
Q
What is intracellular cell signaling
A
- Integrate information of biological signals
2. Make response to biological signals
3
Q
Components of simplistic conceptual model of cell signaling
A
- Signal / biological molecules (chemical: hormone, electrical: nerve impulse, light)
- Switch: must have ability to recognise signal and activate reaction (Enzyme / ion channels)
- Chemical reaction
- Response
4
Q
Realistic model for cell signaling
A
- Cellular response is based on many pieces of biological signals
- Output of each reaction constitute final cellular response
- Crosstalk/ coordination between switches (allow flexibility of response)
- No one switch can control all reactions
- Hierachical relationship between switches
- Network of switches: allow integration of signals
- Relative strength of signals contribute to overall response
- Sequence of phosphorylation can affect outcome
- Control size of response in proportion to strength of signal (switch on/off ratio)
5
Q
Mechanism of receptor kinase
A
- Ligand binding causes receptor kinase to dimerise —> increase in protein kinase activity
- Phosphorylate other protein/enzymes
6
Q
***Mechanism of G-protein coupled receptor
A
- Ligand binding —> conformational change of receptor
- Binding of G-protein to the receptor
- GDP replaced by GTP on G-protein
- Activated alpha subunit + Activated beta-gamma subunit (separate)
- G-protein alpha subunit bind to adenylate cyclase (also in membrane) —> ATP —> cAMP + 2 Pi
- cAMP (second messenger) activate protein kinase A —> downstream signals
- GTP —> GDP —> inactivated alpha subunit back to original position
7
Q
Second messenger
A
- cAMP —> activate protein kinase A
- IP3 —> Calcium release from ER —> activate protein kinase
- DAG —> activate protein kinase
