Term
| Why cells communicate / 4 examples of cell signaling mechanisms / signal transduction pathway deff. |
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Definition
| need to coordinate activities for development / hormone action, enzyme action, cancer research, rearrangement of cytoskeleton / a series of steps by which a signal on a cell's surface is converted into a specific cellular response |
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Term
| how cell communication is basic homeostasis |
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Definition
| cells communicate with eachother to respond to changes in the environment and stuff |
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Term
| types of local ("face to face") signaling: direct contact / cell to cell recognition |
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Definition
direct contact: cell junctions that allow signaling molecules to pass readily between adjacent cells (plasmodesmata, gap junction)
cell to cell recognition: immune system has antibody molecules that bind to antigens |
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Term
| types of local ("sticky note") signaling: local signaling / growth factors / paracrine signaling / synaptic signaling |
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Definition
local signaling/regulators: local regulators are released by signaling cell and influence cells nearby
growth factors: compounds that stimulate nearby target cells to grow and multiply
paracrine signaling:cell releases signal molecules that travel short distances to target cells. Sometimes TC is also the cell that needs the signal molecule, such is called autocrine signaling ( tumer cells)
synaptic signaling: 2 nerve cells come to gether at the synapse, where electrical energy is converted to chemical energy to transfer molecules between nerve cells, then back to electrical energy (removing hand from hot plate) |
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Term
| long distance ("mailing a letter") signaling: hormones / nerve signal transmission / similarity |
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Definition
hormones: cells release molecules into blood vessels that travel to other parts of the body, and slow signal in response to a stimulus. aka endocrine signaling. (testosterone says "get strong")
nerve signal transmission: local synapse travels all the way to the brain - long distance - causing a faster response (removing hand from hot plate)
similarity: both are cellular response to stimuli |
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Term
| three stages of cell communication (communication via direct contact or secreting local regulators like growth factors or neurotransmitters) |
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Definition
RECEPTION: specific ligand (signal molecule coming from outside of cell) is detected by target cell
TRANSDUCTION: conversion of the signal to a form that can bring aout a specific cellular response
RESPONSE: specific cellular response to the signal molecule (opening gates, releasing hormones, etc) |
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Term
| RECEPTION: what happens / example of plasma membrane receptors |
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Definition
| signal molecule (hormone, bacteria, w.e.) called ligand binds to a specific receptor protein which causes the protein to change 3D shape. this activates transduction then is usually reversed so the protein can be used again / insulin is a ligand that will bind to a specific receptor that will send signals to other proteins to get more glucose transporters |
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Term
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Definition
| receptors in cytoplasm or nucleus where signal molecules must cross cell membrane, ligands must be hydrophobic or very small to pass through phospholipid bilayer (ex. steroid testosterone, estrogen, thyroid hormone, nitric oxide gas, or TRANSCRIPTION FACTORS (proteins that control which genes are transcribed into mRNA) |
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Term
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Definition
| receptor usually transmembrane and water-soluble (polar) ligand binds to extracellular side, ligand can't go through so instead it binds to membrane protein receptors that change shape or aggregates |
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Term
| 3 main membrane receptors |
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Definition
| G protein-linked receptors, receptor tyrosine kinases, and ion channel receptors (all recieve ligand, have conformational change, and deliver signal) |
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Term
| G-protein linked receptors: how it works / where it's found / how it's regulated |
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Definition
| ligand binds to receptor called "G protein linked" (7 alpha helixes) which then changes 3D shape that activates G-proten w/ GDP binded ("G-protein linked" activates G-protein by binding to it then changing GDP to GTP)... then G-protein binds to and activates an enzyme that will pass signal on (so G-protein ultimately binds to receptor, GDP/GTP, and enzyme) / found widespread in embryonic development, sensory reception, and bacterial infections / regulated when GTPase hydrolyzes GTP to GDP by GTPase so the G protein is unactivated and can be reused |
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Term
| KINASES (and ase in general) |
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Definition
| enzymes that phorphorylates (ATP-->ADP so extra phosphate can activate a protein) can regulate many proteins in a cell (all of the ones till a response even!) (also GTP->GDP by GTPase) and abnormal kinase activity may contribute to cancer |
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Term
| receptor tyrpsine kinases: what happens / where it's found / how it's regulated |
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Definition
| 2 ligands binds to two separate inactive polypeptides, that then come together to form a DIMER (dimer=2 things) and are phosphorylated/activated by kinases using 6ATP that can then activate relay proteins by changing their shape when the proteins bind to tyrosine on the dimer...these proteins then trigger transduction pathways to form a cellular response / found in cell growth and cell reproduction / after response is complete the ligand can be released |
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Term
| ion channel receptors (aka ligand-gated ion channels): what happens / when it's used |
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Definition
| Na+, Cl-, K+, and Ca+ ions use a channnel that can prevent backflow to be pumped against their gradient...once they flow through the channel they change the ion concentration in the cell which causes a cellular response / usually in muscular and nervous system |
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Term
| transduction phosphorylation cascade / protein phosphatases |
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Definition
| ligand + receptor --> activated relay molecule --> many activated proteins through phosphorylation --> an eventual response / enzymes that dephosphorylate (remove phosphate groups) from protein kinases to deactivate / turn off the signal of these enzymes so they can't energize any reactants, so the cell doesn't get more than it needs of anything (always checks and balances!) |
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Term
| first messenger vs. second messenger (2 types) |
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Definition
| ligand that binds to membrane receptors vs. smal, non-rotein, water-soluble molecules or ions that initiate a phosphorylation cascade once activated that creates a cellular response... (cyclic amp aka camp and calcium ions) |
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Term
| cyclic amp: what happens / example / how it's regulated |
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Definition
| ligand binds to receptor protein like usual, but this time it activates adenylyl cyclase (protein on cell embrane that takes ATP and transofms it to cAMP) so a huge amount of cAMP is produced, then this cAMP activates protein kinase a... this then broadcasts signal to cytoplasm where lots of proteins are signaled that causes a large result / ligand epinepherine is sent to muscle or liver cell that causes glycogen breakdown to go through cellular respiration (fight or flight in a dark alley (^hearbeat, etc)) / phosphodiesterase converts cAMP to AMP becuase the cell doesn't need to waste energy if there's enough response |
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Term
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Definition
| cell membrane was separated from the cell contents, then epinehperine was introdiced into both but neither had a response. this showed that the 2nd messenger was needed to communicate between the two what to do with the epinepherine to get a response |
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Term
| diabetes (2 different types) / caffeine |
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Definition
| one type where theres more than enough insulin (ligand) but the receptors aren't working, the other where there is just not enough insulin which is easier becuase you can just pump it in / when someones stressed or working too hard for too long, adenosine binds to receptors in brain that will signal proteins to make you drowsy and not alert through a cascade of events (a protective devise so you don't fry your brain!) however with caffeine, it binds to the same brain receptors to block the pathway and keep your brain active, AND it blocks phosphodiesterate in epinephrin production which allows cAMP to keep going so you stay alert there too (fight or flight=epinephrin) |
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Term
| specific insuline pathway |
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Definition
| 1M ligand (insulin) bonds to 1M receptor (G protein linked) to activate 1M G-protein that activates around 20M of cAMP that forms around 20M of PKinase A per cAMP, then each PKA activates around 1000M of gycogen phosphorylase (glucose transporter) that helps break glycogen into glucose to perform respiration (from 1--> 400,000 |
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Term
| calcium ions: what happens / examples |
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Definition
| similar to cAMP in G-protein pathway, except this time signal molecules like neurotransmitters, growth factors, or hormones increase [Ca] in cytosol that triggers various signaling pathways / muscle cell contraction, cell division, greening in plants, G-protein and tyrpsine kinase pathways |
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Term
| RESPONSE: what happens / signal amplification / specificity of cell signaling |
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Definition
| transduced signal finally triggers a specific response protein that triggers cellular response either in cytoplasm or nucleus that causes many responses including regulation of enzyme activity and synthesis, turning off or on genes in nucleus, or activating transcription factors / at each step, response is amplified so number of products is much bigger than in preceding step (see insulin example) / response of a particular cell depends on its particular collection of signal receptor proteins, relay proteins, and response proteins |
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