ap bio unit 4: cell communication

autocrine

signal to self

juxacrine

signal to neighboring cell by direct contact

cell junctions

mcules pass from cell to cell w/o needing to cross lipid bilayer (e.g. plasmodesmata btwn plant cells)

cell-cell recognition

surface mcules on pathogens bind to one another (pathogen recognition by immune cells)

ligand

signaling molecule

receptor

binds to ligand and initiates response

paracrine signlaing

nearby cells (tissue) signal each other w/ ligands (e.g. neuron synapse)

endocrine signaling

cells transmit hormones that target distant cells

lipid soluble ligands

nonpolar (steroids) go straight to intracellular receptor which goes to nucleus

water soluble ligands

polar; attach to surface receptors that initiate signal transduction until it reaches the nucleus

amine derivatives

have properties of water and lipid soluble

extracellular receptor

usually an ion channel that changes conformation based on whether or not a ligand is present

structural protein

change the shape of the cell when activated

enzyme target

altered metabolism or cellular function

gene regulatory protein (transcription factor)

altered gene expression and types and amounts of protein produced (bind w/ dna to promote transcription)

positive feedback

as a response, the stimulus is increased (e.g. platelets for blood clots produce chemicals that attract more platelets)

negative feedback

as a response, stimulus is decreased (if it is hot we sweat)