Cellular Communication -All cells communicate -Eukaryotes and prokaryotes!

Communication process usually involves the plasma membrane 2 types: local and long-distance

Local Signaling Direct contact Gap junctions or plasmodesmata Cytoplasms of cells directly connected Animal cells also by direct contact between membrane-bound molecules Use of messenger molecules for short-distance communication Paracrine signaling Synaptic signaling Glycoproteins in regard to animal cells. Important in immunity Notice the vesicles of material being released by exocytosis Paracrine signaling: a secreting cell acts on nearby target cells by discharging molecules of a local regulator into the extracellular fluid (growth factor)

Long-Distance Use of hormones to travel long distances Nervous and endocrine system Talk about long-distance later in the spring when we go over the two systems

3 Stages of Cell Signaling Reception- target cell detects the signaling molecule- binds to a receptor protein either on the cell’s surface or inside the cell Transduction- series of steps that converts the signal to a form that elicits a response. Usually requires a change in a cheries of differenct molecules this is known as the signal transduction pathway. Molecules involved with this is known as the relay molecules. Response. Any type of activity. Example might be enzyme activity

Reception Signaling molecule= ligand Causes a change in the receptor protein Most receptors are found in the plasma membrane Ligands are water-soluble Ligand- molecule that specifically binds to another molecule

Receptors in the Plasma Membrane Two Major Types G protein-coupled receptors (GPCR) Ligand-gated ion channels Epinephrine uses a GPCR pathway. Different types of G proteins. G proteins are similar in structure, suggesting that these signaling systems evolved very early in the history of life!!! Different diseases can interfere with G protein functioning.

Ligand-gated ion channel Membrane receptor that has a region that can act as a gate for ions when the receptor assumes a certain shape. Critical for nervous system. The ions coming in cause the cellular response

Intracellular Receptors Cytoplasm or nucleus Hydrophobic signals- ex. steroids Remember- a steroid is a type of lipid

Transduction by Cascade Transduction of cell signaling usually involves multiple steps Gives possibility of signal amplification Signal transduction pathway usually involves proteins Change in shape of a protein Phosphorylation Multiple step – transmit signal to multiple molecules at the next step of the series, and the result can be a large number of activated molecules at the end.

Protein Changes Protein kinase- adds phosphate groups from ATP to a protein Protein phosphatases removes phosphate groups- making them inactive again. Turns off cascade when signal is no longer present

Second Messengers Small, non-protein, water-soluble molecules Ex. Cyclic AMP or Ca2+ Easily move through cytoplasm Activate other proteins Epinephrine Cyclic adenosine monophosphate. Each molecule of adenylyl cyclase can catalyze the synthesis of many molecules of cAMP

Cholera and interruption of signaling Disruption of GPCR Signal doesn’t turn off