1. Cellular Communication
-All cells communicate
-Eukaryotes and prokaryotes!

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

3. 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)

4. 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

5. 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

6. 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

7. 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.

8. 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

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

10. 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.

11. 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

12. 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

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