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Phys ch 5
exam 1 material
| Question | Answer |
|---|---|
| signal transduction | sequence of events in the cell leading to the cell's response to that messenger |
| receptors are either located.. | on the cell's plasma membrane or inside the cell, cytosol or nucleus |
| More common type of receptor location | in the cell membrane because many messengers are water soluble and cannot diffuse across the membrane |
| receptor mlx is | protein or glycoprotein |
| plasma membrane receptors | can transduce signals without interacting with DNA, transmembrane proteins |
| segments of plasma membrane receptors | hydrophobic segments within membrane, hydrophilic segments extending into extracellular and intracellular fluid |
| intracellular receptors location | cytosol or nucleus |
| intracellular receptors | ALL transduce signals through interactions with genes |
| segments of intracellular receptors | segment that acts as regulatory site, segment that binds to messenger, segment that binds to DNA |
| 4 major features that define interactions between receptors and ligands | specificity, affinity, saturation, competition |
| specificity | the ability of a receptor to bind only one type or a limited number of structurally related types of chemical messengers |
| affinity | the strength with with a chemical messenger binds to its receptor |
| saturation | the degree tow which receptors are occupied by messengers |
| competition | ability of a molecule to compete with a natural ligand for binding to its receptor |
| first messenger | binds to particular cells based on receptor specificity |
| antagonist | compound that blocks the action of a chemical messenger |
| example of antagonist | beta blocker, competes with epinephrine and norepinephrine to decrease blood pressure |
| agonist | used therapeutically to mimic the messenger's action |
| example of agonist | phenylephrine and oxymetazoline, in nasal sprays, mimic epinephrine to decrease fluid leakage |
| down-regulation | reduces the target cell's responsiveness to frequent / intense stimulation by a messenger, desensitizes it |
| what is down-regulation an example of? | local negative feedback system |
| internalization | messenger/receptor complex is taken into the cell by receptor-mediated endocytosis |
| up-regulation | increased sensitivity, cells exposed for a prolonged period to very low concentrations of a messenger, has more receptors for it |
| receptor activation | initial step leading to a cell's response to the messenger |
| signal transduction pathways | diverse sequence of events that link receptor activation to cellular responses |
| pathways initiated by lipid soluble messengers example | steroid/thyroid hormones, aka nuclear receptors, in most cases inactive receptors already reside in nucleus |
| first part of lipid soluble messengers pathway | messenger diffuses out of capillaries from plasma to interstitial fluid, messenger diffuses across lipid bilayer of plasma membrane and nuclear envelope, binds to receptor |
| second part of lipid soluble messengers pathway | activated complex functions as transcription factor, binds to DNA @ regulatory region, increases rate of transcription into mRNA |
| what does pathways initiated by lipid-soluble messengers result in? | increase in cellular concentration of the protein being secreted |
| 4 types of pathways being initiated by water-soluble messengers | receptors that are ligand-gated ion channels, that function as enzymes, that interact with cytoplasmic janus kinases, and G protein coupled receptors |
| pathways initiated by water-soluble messengers | cannot enter cells by diffusion, exert their actions on cells by binding to the extracellular portion of receptor proteins embedded in plasma membrane |
| example of water-soluble messenger | polypeptide hormones, neurotransmitters, paracrine/autocrine |
| first messengers | extracellular chemical messengers that reach the cell and bind to specific plasma membrane receptors |
| second messengers | substances that enter or are generated in the cytoplasm as a result of receptor activation |
| signaling by receptors that are ligand-gated ion channels | activation of receptor by a first messenger leads to conformational change of receptor, forms open channel through plasma membrane |
| signaling by receptors that function as enzymes | binding of first messenger changes conformation so that enzymatic portion on cytoplasmic side is activated, phosphorylated its own tyrosine residues |
| exception to protein kinase in enzyme water-soluble messengers | receptor functions as both receptor and guanylyl cyclase to catalyze formation of cGMP(acts as second messenger) |
| signaling by receptors that interact with cytoplasmic janus kinases | binding of first messenger, activates janus kinases, results in synthesis of new proteins |
| most common water-soluble messenger pathway | G protein coupled receptors |
| signaling by G-protein-coupled receptors | binding, increasing affinity of alpha subunit for GTP, dissociates from beta and gamma, links up with ion channel or enzyme, either leads to change in membrane potential or second messenger generation |
| 3 subunits of G proteins | alpha, beta, gamma |
| two most common effector protein enzymes regulated by G proteins | adenylyl cyclase and phospholipase C |
| cAMP acts as a | second messenger |
| adenylyl cyclase pathway | binding, activates Gs protein, activates adenylyl cyclase, catalyzes cytosolic ATP to cAMP |
| Gq protein activates.... | phospholipase C |
| phospholipase C catalyzes breakdown of.. | PIP2 to DAG and IP3 |
| DAG and IP3 are examples of.. | second messengers |
| DAG function | activates protein kinase C, which then phosphorylates a large number of proteins |
| IP3 function | binds to receptors located on endoplasmic reticulum, ligand gated Ca2+ channels open when bound to IP3 |
| ____ is maintained at low concentration in cytosol | Ca2+ |
| mechanisms in which stimulation of a cell leads to increase in cytosolic Ca2+ concentration | receptor activation and opening of voltage-gated Ca2+ channels |
| mechanisms by which an increase in cytosolic Ca2+ induces cell's responses | Ca2+ binding to calmodulin, and Ca2+ combines with Ca2+ binding proteins, alters their functions |
| Ca2+ binding with calmodulin | INACTIVE WITHOUT CA2+, Ca2+ binds, changes calmodulin shape, activates inhibits calmodulin-dependent protein kinase |
| ways that activity in signal transduction pathways cease | first messenger is removed, or receptor is inactivated |
| ways that first messenger can be removed | can be diffused away or metabolized by enzymes |
| ways that receptors can be inactivated | chemically altered, phosphorylation prevents further G-protein binding, plasma membrane receptors may be removed |
| lipid-soluble messengers pathway | slow, not very common |
| example of lipid soluble messenger | steroid hormones, estrogen |
| lipid-soluble messengers always.. | initiate transcription or translation |
| lipid soluble messengers ONLY | act through DNA, transcription translation, don't have functions of cAMP |
| cAMP can.. | act as a lipid soluble messenger in some cases, activate DNA transcription/translation |
| where in the cell is there a high concentration of calcium? | endoplasmic reticulum |
| where in the cell is there a low concentration of calcium? | cytosol |
| why is phospholipase C unique? | because it can break down molecules that are present IN the cell membrane |
| most common way a signal is terminated | decrease in first messenger |
| 3 ways a decrease in first messenger can happen | enzyme breakdown, diffuse away, endocytosis |
| 3 ways signal can be terminated | decrease in first messenger, receptor is altered, membrane receptor removed |
| STAT in JAK pathway | designed to bind to JAK kinase and shut it off |
Created by:
thomask9