signal transduction Cell-cell contact via gap junctions or plasmodesmata; signal molecule passes between cells Cell-cell recognition molecule binds to specific receptor; “receptor-ligand interaction”

When the ligand binds, other molecules are produced within the cell “second messengers” relay the signal from interior of cell May trigger cell activity and/or gene expression

Things that can trigger cell signaling G-protein-linked receptors tyrosine kinase receptors ion-channels

Many different types of G proteins can interact with different cellular proteins Vision Smell Acetylcholine receptors: one “family” are ion channels (contraction), another are G protein receptors (relaxation) Developmental pathways What does G protein activation accomplish? Activation of second messenger system cAMP calcium Levels are elevated

Several families of tyrosine kinases

Na channel

Photoreceptor – rods and cone

Taste Five different groups: Sweet Salty Bitter Sour Umami The different tastes can be caused by ion channels, receptor proteins and other signal pathways

Use your receptors to smell and taste things!