Module 9 Flashcards
Signalling Cell
The source of a signalling molecule.
Responding Cell/Target Cell
The cell that receives information from the signalling molecule.
Receptor Activation
The turning on of a receptor which often occurs when a signalling molecule binds to a receptor on a responding cell.
Response
A change in cellular behaviour such as activation of enzymes or genes following a signal.
Paracrine Signalling
Signalling by a molecule that travels a short distance to the nearest neighbouring cell to bind its receptor and lead to a response. (20 cell distance)
Endocrine Signalling
Signalling by molecules that travel through the bloodstream.
Contact-Dependent Signalling/Juxtacrine Signalling
Signalling that involves direct contact between two cells, typically a ligand on one cell with a receptor on the other cell. The signalling molecule is not released from the cell, but instead remains associated with the cell membrane.
Nonpolar Signalling Molecules
Molecules that enter the cell and bind to receptors found in the cytoplasm.
G Protein
A protein that binds to the guanine nucleotides GTP and GDP. Active when bound to GTP. Inactive when bound to GDP.
Phosphatase
An enzyme that removes phosphate groups from another molecule.
Second Messenger
Signalling molecules found inside cells that relay information to the next target in the signal transduction pathway.
Protein Kinase A (PKA)
An enzyme that becomes activated by cAMP.
Signalling Molecule/Ligand
The carrier of information transmitted when the signalling molecule binds to a receptor.
Signal Transduction
The process in which an extracellular molecule acts as a signal to activate a receptor which transmits information to the cell through the cytoplasm. The receptor transmits a message to the cell through the cytoplasm.
Signal Termination
When the ligand dissociates from the receptor and the cell’s response goes in reverse.
Autocrine Signalling
The signalling cell and the responding cell are one and the same.
Ligand-Binding Site
The specific location on the receptor where a signalling molecule binds.
Polar Signalling Molecules
Molecules that cannot enter the cell and bind to receptors outside of the cell.
G Protein-Coupled Receptor
A receptor that couples to G proteins, which bind to the guanine nucleotides GTP and GDP.
Receptor Kinase
A receptor that is an enzyme that adds a phosphate group to another molecule.
Ion Channels
A channel-like membrane protein that regulates the flow of ions across the cell membrane.
Cyclic AMP (cAMP)
A second messenger.
Binding Affinity
The tightness of the binding between the receptor and the signalling molecule.
Cellular Communication Elements
1) A Signalling Cell
2) A Signalling Molecule
3) A Receptor Protein
4) A Responding Cell
Receptor Protein
The molecule on the responding cell that binds to the signalling molecule.
Cell Signalling Process
1) Receptor Activation
2) Signal Transduction
3) Response
4) Termination
Termination
The stopping of the response of a cell triggered by a signal.
Growth Factor
A type of signalling molecule that causes the responding cell to grow, divide, or differentiate.
Neurotransmitters
A type of signalling molecule released from a neuron.
Adenylyl Cyclase
Converts the ATP into cyclic AMP (cAMP).
First Messenger
Transmit signals from outside the cell to a receptor.
Cell Signalling
Transferring information from the outside of the cell to obtain a response inside the cell.
α Subunit
Part of the G protein that binds to either GDP or GTP.
β Subunit
Part of the G protein.
γ Subunit
Part of the G protein.
Kinases
Enzymes that phosphorylate target proteins.
Dimerization
The receptors associate into dimers (2 receptors into 1).
Ligand-Gated
Respond to binding of a signalling molecule.
Voltage-Gated
Respond to changes of voltage in the cell.
Mechanically-Gated
Respond to force applied to the cell.
Closed Gate
Prevents the movement of the ion.
Open Gate
Allows the movement of the ion.
Low Peptide Levels
Low density of bacteria. Gene expression is turned off.
High Peptide Levels
High density of bacteria. Gene expression is turned on allowing DNA uptake from the environment.
Hormones
Chemical signalling molecules.
Types of Protein Receptors
1) G Protein-Coupled Receptors (GPCRs) (fast and quick)
2) Receptor Kinases (long-lasting)
3) Ion Channels
Receptor Kinase Example
1) PDGF activates receptor.
2) Ras gets activated and activates kinase 1.
3) Kinase 1 activates kinase 2.
4) Kinase 2 activates kinase 3.
5) Kinase 3 activates transcription factors for gene expression.
6) The pathway is terminated when the GTP is replaced by GDP on Ras.
