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