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Chemical Messengers areas of interaction cell surface receptors / external receptors most in cell membrane integral proteins internal receptors most in cytoplasm or nucleus entering chemicals must be hydrophobic and like lipids) examples steroids thyroid hormones (T3 T4) vitamin E, A, D and K (fat soluble) affects DNA receptors ligands hormones neurotransmitter like a key matching a receptor only from body, not drugs messenger that carries information to cell with appropriate receptor binds to internal or external receptor membrane receptors integral proteins single protein can span the membrane penetrate through multiple times most commonly 7 times most commonly alpha helix shape ligand related types ligand gated ion channels chemicals outside cell GABA actytolecholine glycin seratonin ATP cGMP cAMP Ca IP3 usually passing Na, K, Ca, or Cl receptors coupled to G protein / G protein associated single chain passing 7 times through membrane G receptor inside examples epinephrine oxytocin norepinephrine G-Proteins have 3 units alpha beta gama in resting state alpha hooked to GDP after reception of ligand, GDP switches for GTP and alpha is broken off with it alpha-GTP unit then interacts with a molecule downstream on the membrane example 1 downstream AC (adenylyl cyclase)) molecule then when hit + ATP results in cAMP (enzymatic action) cAMP than affects/activates PK (protein kinase)-> PKp and/or phosphotase GP (Glycogen phosphorylase) + PKp = GPp GPp causes glycogen break down to release glucose also PK -> GS (glycogen synthase) to become GSp to stop glycogen production example 2 alpha-GTP hits PL (phospholipase) and it releases IP3 or Arachidonic Acid IP3 then reacts with another receptor affects Ca release to activate cell function PIP2 activated by PL ->  IP3 (idenosin triphosphate) (leaves membrane) and DAG (stays in membrane) IP3 goes to ER to open calcium channels for release Phospholipids activated by PL -> Arachidonic Acid goes to cycloxygenase (COX) Prostoglandins aspirin stops COX -> Prostoglandins 5-Lipoxygenase (LOX) Leukotrienes both create the inflamatory response cortisol inhibits creation of AA catalytic receptors cross membrane once act as enzymes - causing a reaction example cytokine receptors receptor receives ligand Product released from associated protein (like PLC) intracellular receptors

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