Key Terms
Example
Neurotransmitters crossing the synaptic gap (20-40 nm) between nerve cells. Signal arrives, electrochemical potential sh
Two categories
Internal receptors and cell-surface receptors. Which one a ligand uses depends on whether it can cross the plasma membra
Once ligand binds
1. Conformational change exposes a DNA-binding site on the receptor 2.
Three domains on every cell-surface receptor
1. Extracellular domain: ligand-binding site (outside the cell) 2.
Tyrosine kinase receptor (key example)
1. Ligand binds two nearby receptors simultaneously 2.
Signal transduction
The conversion of an extracellular signal into an intracellular signal. Happens only with cell-surface receptors; they c
Amplification
One ligand activates one receptor, which can activate many downstream copies; the signal grows as it moves through the c
Result
Rapid glucose availability for immediate energy (fight-or- flight). The futile cycle of building and breaking glycogen s
Quorum sensing triggers a positive feedback loop
More bacteria produce more autoinducer, which promotes more autoinducer production.
Biofilms
Complex colonies (often multi-species) that coordinate toxin release via quorum sensing. Found on medical implants; life
Ligand
Signaling molecule that binds a specific receptor Receptor: protein in or on a target cell that binds a ligand Signal tr
Oncogene
Gene with potential to cause cancer when mutated Autoinducer: bacterial signaling molecule for quorum sensing Quorum sen