| A | B |
|---|
| Lateral diffusion | Movement of phospholipids molecules within a monolayer. One lipid diffuses length of cell in about 1 sec. |
| Flip-flop | Migration of phospholipids from one monolayer to the opposite. Occurs less than once a month per lipid unless catalyzed. |
| Phosphatidylserine, phosphatidylethanolamine | The major lipids in the inner monolayer of many mammalian plasma membranes. Serine carries a negative charge. |
| Phosphatidylcholine, sphiongomyelin | The major lipids in the outer monolayer of many mammalian plasma membranes. |
| Contact dependent, paracrine, synaptic, endocrine and autocrine signalling | Forms of intracellular signaling. |
| Nitric oxide (NO) | Synthesized from arg by NO synthase. Causes smooth muscle, e.g., blood vessels, to relax by stimulating guanylyl cyclase. |
| Nucelar receptor superfamily | Intracellular receptors for hydrophobic signal molecules. The receptor-ligand complex acts as gene regulatory protein in nucleus. |
| Steroid hormones, thyroid hormones, retinoids, vitamin D | Small hydrophibic molecules that diffuse across the plasma membrane and bind to receptors of the nuclear receptor family. |
| Ion-channel-linked, G-protein-linked and enzyme-linked receptors | The three major classes of cell-surface receptor proteins. |
| Receptor sequestration and down-regulation | Desensitization mechanisms by endocytosis of receptors (former) optionally followed by degradation in lysosomes (latter). |
| Trimeric GTP-binding proteins (G proteins) | GTP-binding protein with subunits alpha, beta and gamma. Split into alpha subunit and beta-gamma complex when active. |
| Cyclic AMP (cAMP) | Second messenger. Synthesized from ATP by adenylyl cyclase, destroyed by cAMP phosphodiesterases. Activates PKA. |
| CRE-binding (CREB) protein | Gene regulatory protein. Binds to the gene regulatory sequence CRE when phosphorylated by PKA. |
| Inositol 1,4,5-triphosphate (IP3), diacylglycerol (DAG) | Second messengers. Produced by hydrolysis of PIP2 by a phospholipase C. Dag necessary for activating PKC. |
| Calcium | Second messenger. Released, e.g., from ER through IP3-gated calcium channels. Necessary for activatinf PKC, and CaM-kinases. |
| Receptor tyrosine kinase, SH2 | Enzyme-linked receptor. Often dimerizes with autophosphorylation and binding sites for SH2 domains when activated. |
| Ras, MAP-kinase | Monomeric GTP binding protein. Activates phosphorylation cascade with MAP-kinase when active. |
