Cell Communication Flashcards
1
Q
Reception
A
- Target cell detects a signaling molecule that binds to receptor protein on cell surface
- Binding btwn signal molecule (ligand) and receptor is highly specific
- Receptors found in plasma membrane of proteins
2
Q
Transduction
A
- Change in receptor’s shape after binding is initial transduction of signal
- Multistep process
- Binding of signaling molecule to receptor
- activation of another protein, another protein, etc. until the protein producing the response is activated
- At each step signal is transduced into different form (phosphorylation/dephosphorylation)
3
Q
Response
A
- Transduced signal triggers a specific response in target cell
- Nuclear and Cytoplasmic
- Regulate the synthesis of enzymes and proteins
4
Q
G protein-coupled receptors (GCPRs)
A
- Cell-surface transmembrane receptors
- Work w/ help of G protein
- Binds to energy-rich GTP
- Receptor receives signaling molecule, GDP leaves
- GTP is released and attaches to inactive enzyme (now active)
- Cellular response
- GTP loses phosphate group, goes back to G-protein coupled receptor via G protein as GDP
- Binds to energy-rich GTP
5
Q
Receptor Tyrosine Kinases (RTKs)
A
- Membrane receptors that transfer phosphate groups from ATP to another protein
- Can trigger multiple signal transduction pathways at once
1. Signaling molecules attach to inactive monomer, becomes phosphorylated dimer
2. ATP–> ADP (uses phosphates)
3. Cellular responses
6
Q
Ligand-gated ion channel
A
- Acts as a gate that opens and closes when the receptor changes shape
- When signal molecule binds as a ligand to the receptor, gate allows specific ions through a channel in the receptor
1. Ligand binds to receptor
2. Channel opens and ions pass through (cellular response)
3. Ligand is removed
4. Channel closes
7
Q
Protein phosphorylation
A
- Widespread cellular mechanism for regulating protein activity
- Protein kinases transfer phosphates from ATP to protein
- Many relay molecules in signal transduction are protein kinases, creating phosphorylation cascade
8
Q
Protein Dephosphorylation
A
-Protein phosphatases rapidly remove the phosphates from proteins
9
Q
Second Messengers
A
- Small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion
- Participate in pathways initiated by GPCRs and RTKs
- Ex: Cyclic AMP and calcium ions
10
Q
Cyclic AMP
A
- Widely used second messanger
- cAMP
- Adenylyl cyclase (enzyme) converts ATP to cAMP in response to extracellular signal
11
Q
Transduction w/ cAMP as 2nd messenger
A
- Signal molecules trigger formation of cAMP
- other components of cAMP pathways are G proteins, G protein-coupled receptors, and protein kinases
- cAMP activates protein kinase A, phosphorylates various proteins
- Further regulation of cell metabolism is provided by G protein systems that inhibit adenylyl cyclase
12
Q
Transduction w/ Ca+
A
-A signal relayed by a signal transduction pathway may trigger an increase in calcium in the cytosol
13
Q
Nuclear and Cytoplasmic Responses
A
- Signalling pathways regulate synthesis of enzymes or proteins by turning genes on or off in the nucleus
- Final activated molecule in signaling pathway functions as transcription factor
- Other pathways may regulate the activity of enzymes rather than synthesis
14
Q
Regulation of the Response
A
- Four aspects of signal regulation
1. Pathway leads to single response
2. Pathway branches, leading to two responses
3. Cross-talk btwn 2 pathways
4. Different receptor leads to a diff response - Enzyme cascades amplify the cell’s response to signal
15
Q
Termination of the Signal
A
- Inactivation of mecchanisms= essential aspect of cell signaling
- If the ceoncentration of external signaling molecules fall, fewer receptors will be bound
- Unbound receptors revert to inactive state
