CELL COMMUNICATION
Dec 14, 2015
CELL COMMUNICATION
YOU MUST KNOW…• THE 3 STAGES OF CELL
COMMUNICATION: RECEPTION, TRANSDUCTION, AND RESPONSE
• HOW G-PROTEIN-COUPLED RECEPTORS RECEIVE CELL SIGNALS AND START TRANSDUCTION
• HOW RECEPTOR TYROSINE KINASE RECEIVE CELL SIGNALS AND START TRANSDUCTION
YOU MUST KNOW…• HOW A PHOSPHORYLATION CASCADE
AMPLIFIES A CELL SIGNAL DURING TRANSDUCTION
• HOW A CELL RESPONSE IN THE NUCLEUS TURNS ON GENES WHILE IN THE CYTOPLASM IT ACTIVATES ENZYMES
• WHAT APOPTOSIS MEANS AND WHY IT IS IMPORTANT TO NORMAL FUNCTIONING OF MULTICELLULAR ORGANISMS
CONCEPT 11.1• EXTERNAL SIGNALS ARE
CONVERTED INTO RESPONSES WITHIN THE CELL
3 STAGES FOR CELL SIGNALING• RECEPTION – THE TARGET CELL’S
DETECTION OF A SIGNAL MOLECULE COMING FROM OUTSIDE THE CELL
• TRANSDUCTION – THE CONVERSION OF THE SIGNAL TO A FORM THAT CAN BRING ABOUT A SPECIFIC CELLULAR RESPONSE
• RESPONSE – THE SPECIFIC CELLULAR RESPONSE TO THE SIGNAL MOLECULE
CONCEPT 11.2• RECEPTION: A SIGNAL
MOLECULE BINDS TO A RECEPTOR PROTEIN,
CAUSING IT TO
CHANGE SHAPE
• THE BINDING BETWEEN A SIGNAL MOLECULE (LIGAND) AND A RECEPTOR IS HIGHLY SPECIFIC
• RECEPTORS ARE FOUND IN 2 PLACES• INTRACELLULAR RECEPTORS –
INSIDE PLASMA MEMBRANE IN THE CYTOPLASM OR NUCLEUS. THE SIGNAL MOLECULE IS HYDROPHOBIC SO IT CAN CROSS THE MEMBRANE
• PLASMA MEMBRANE RECEPTORS – BIND TO WATER-SOLUBLE LIGANDS
G-PROTEIN-COUPLED RECEPTOR
• MEMBRANE RECEPTOR THAT WORKS WITH THE HELP OF A G-PROTEIN
• G-PROTEIN BINDS TO SIGNALING MOLECULE AND CAUSES A CHANGE IN THE RECEPTOR CAUSING THE INACTIVE G-PROTEIN TO BECOME ACTIVE
• G-PROTEIN ACTIVATES THE ENZYME• MOLECULAR SHAPE CHANGES ARE
TEMPORARY
RECEPTOR TYROSINE KINASE• SIGNAL MOLECULES BIND TO THE
RECEPTORS THAT FORMS A DIMER• DIMER ADDS A PHOSPHATE FROM AN
ATP MOLECULE• THE ACTIVATED RECEPTOR PROTEIN
INITIATES MULTIPLE CELLULAR RESPONSES FOR EACH PHOSPHORYLATED TYROSINE
LIGAND-GATED ION CHANNELS
• SPECIFIC SIGNAL MOLECULES CAUSE THE CHANNELS IN A MEMBRANE TO OPEN OR CLOSE, REGULATING THE FLOW OF SPECIFIC IONS
CONCEPT 11.3• TRANSDUCTION: CASCADES OF
MOLECULAR INTERACTIONS RELAY SIGNALS
FROM RECEPTORS
TO TARGET
MOLECULES
IN THE CELL
PHOSPHORYLATION CASCADE• A MULTISTEP PATHWAY THAT
GREATLY AMPLIFIES THE SIGNAL• ENZYMES CALLED PROTEIN KINASES
PHOSHORYLATE AND ACTIVATE MANY PROTEIN AT
THE NEXT LEVEL• ALLOWS FOR A LARGE CELLULAR RESPONSE
SECOND MESSENGERS• SMALL, NONPROTEIN WATER-
SOLUBLE MOLECULES OR IONS• ONCE ACTIVATED, THEY CAN INITIATE
A PHOSPHORYLATION CASCADE RESULTING IN A CELLULAR RESPONSE
• EX. CALCIUM ION AND CYCLIC AMP
CONCEPT 11.4• RESPONSE: CELL SIGNALING
LEADS TO REGULATION OF TRANSCRIPTION OR CYTOPLASMIC ACTIVITIES
PURPOSE OF SIGNALING PATHWAYS
• REGULATE PROTEIN SYNTHESIS, USUALLY BY TURNING SPECIFIC GENES ON OR OFF IN THE NUCLEUS
• OFTEN ACTS AS A TRANSCRIPTION FACTOR
CONCEPT 11.5• APOPTOSIS INTEGRATES
MULTIPLE CELL SIGNALING PATHWAYS
APOPTOSIS• PROGRAMMED CELL
DEATH• CELL IS SYSTEMICALLY
DISMANTLED AND DIGESTED
• TRIGGERED BY SIGNALS THAT ACTIVATE A CASCADE OF “SUICIDE” PROTEINS IN THE CELLS