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| external signals are changed into a form that brings about a response (signal transduction pathway) | ||
| gap junctions in animals; plasmodesmata in plants | ||
| secreted by signaling cell travel short distance to a receiving cell; local signaling | ||
| with electrical and chemical signals between a nerve cell and its target cell | ||
| long distance signals in plants and animals | ||
| reception, transduction, response | ||
| receives signal by target cell; specifically binds to a certain cell type (target cells); chemical signal (ligand) binds to a receptor; most of the receptors are cell membrane proteins because most signals are too big to diffuse through membrane | ||
| receptor protein's shape is changed by the binding of the chemical signal; binding causes changes to occur in the cell that will bring about a response | ||
| a specific cellular response is triggered | ||
| plasma membrane proteins with receptors on them; receives epinephrine, hormones, neurotransmitters | ||
| chemical signal binds to G protein coupled receptor, receptor changes shape and binds to a G-protein inside of plasma membrane; G protein will give off its GDP and accept GTP and is activated; moves along inside of plasma membrane and binds to another membrane protein (enzyme) to activate it; this causes cell response | ||
| G protein acts as a GTPase and removes the P (Though hydrolysis), GTP to GDP | ||
| plasma membrane receptors used by growth factors; kinase is an enzyme that transfers a phosphate group from one molecule to another (in this, transfer P from ATP to tyrosine on the tail) | ||
| 2 ligands bind to 2 tyrosine-kinase receptors; causes 2 receptors to bind together and form a dimer; activates the tail and they phosphorylate each other; other proteins bind to the phosphorylated tails and cause a cellular response; 1 dimer can activate 10 or more different proteins simultaneously; if they bind without a chemical signal, may cause cancer | ||
| plasma membrane receptors, signal between nerve cells, have a gate that can open or close a channel; when ligand binds, the channel opens or closes, allowing flow or stopping flow of ions | ||
| inside cell in cytosol or in nucleus; steroid and thyroid hormones, nitric oxide all use intracellular receptors; testosterone: binds to receptor and activates it; activated receptor enters nucleus, binds to DNa and acts as a transcription factor which makes DA make RNA and proteins | ||
| usually multistep pathways involving lots of P switching or moving of molecules that act as messengers; lots of protein-protein interactions | ||
| phosphorylation cascade; phosphorylation can usually increase or decrease the activity of a protein; protein phosphatases remove phosphates (dephosphorylates) to turn off signal | ||
| signal molecule (first messenger) binds to a cell membrane receptor, activates G protein which activates adenylyl cyclase which converts ATP to cAMP; cAMP activates other proteins to cause response; photodiesterase returns cAMP to AMP | ||
| signal molecules bind to either a G-linked protein receptor or a tyrosine-kinase receptor; produces IP3 which acts as second messenger; binds to ligand-gated calcium channel on the ER and opens it to release Ca ions which act as the second messenger and cause a response; calcium ions are actively pumped back onto the mitochondria, ER and outside the cell | ||
| large relay proteins to which several other relay proteins are attached | ||
| programmed cell death; cellular agents chop DNA, organelles, other cytoplasmic stuff; cell shrinks and becomes lobed (blebbing); cell's parts are packaged into vesicles and digested by scavenger cells; cleans up cells, helps in embryonic development, develop nervous system, immune system | ||
| caenorhabditis elegans (nematode) | ||
| external- death sinaling ligand binds to receptor; internal- from nucleus in response to DNA damage, from ER in response to numerous misfolded proteins |
