Lecture Notes for 9/29/15
Lecture Notes for 9/29/15 BIOL 1305 - 010
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This 3 page Class Notes was uploaded by Sofia Romero on Wednesday September 30, 2015. The Class Notes belongs to BIOL 1305 - 010 at University of Texas at El Paso taught by Hsin-i Lin in Fall 2015. Since its upload, it has received 94 views. For similar materials see General Biology - 15965 in Biological Sciences at University of Texas at El Paso.
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Date Created: 09/30/15
9292015 Biology Lecture Notes Key Red is Vocabulary Green are Examples and Orange is important information There are two types of active transport in cells Primary active transport which involves the hydrolysis of ATP for energy Secondary active transport which uses the energy from an ion concentration gradient or an electrical gradient An example of an active transport is a sodiumpotassium pump This pump is a membrane that pumps Na out of the cell and K in 1 molecule of a sodiumpotassium pip can move 2K in and 3 Na ions out Active transport moves against the gradient directly while secondary active transport uses ATP indirectly Ex Secondary active transport may begin with the passive diffusion of a few ions or may involve a carrier protein that transports a substance and ions Macromolecules however are too large to pass through the membrane so instead go through vesicles Endocytosis the cell takes in molecules through vesicles Exocytosis the cell releases molecules to the outside of the cell There are 3 different types of endocytosis Phagocytosis where part of the membrane engulfs a large particle or cell and a food vesicle phagosome forms Pinocytosis where part of the membrane swallows water and a drinking vesicle forms These vesicles are smaller than phagosomes Receptor mediated endocytosis where part of the membrane is coated and therefore attracts a certain type of molecule It then breaks off and forms a coated vesicle In all three types the membrane invaginates the molecule lnvaginates turns back in on itself in order to form a pouch Exocytosis moves materials out of cell in vesicles The vesicle membrane fuses with the cellular membrane therefore releasing the contents into the environment A signal transduction pathway is a sequence of molecular eventschemical reactions that can lead to a cellular response when the receptor is activated Signal Chemical Response Exocytosis Only cells with the necessary receptors can respond to a signal the only way for the pathways to be opened is for the cell to be able to senserespond to the signal Parts of a signal transduction pathway a signal receptor and response Signal Examples Autocrine affect the same cells that release them Paracrine diffuse and affect nearby cells Hormones travel to different cells Common mechanism of signal transduction is allosteric regulation Aosteric regulation is the binding of a molecule at a site other than the proteins active site This can affect signal transduction A signal molecule ligand ts into the 3D site on the receptor protein The ligand binding causes 3D shape change which then initiates a cellular response After this ligands are not metabolized anymore although they can expose an active site Binding is reversible An inhibitor antagonist can bind instead of a ligand Receptors are classi ed by location This is determine by whether or not their ligand can diffuse through the membrane Cytoplasmic receptors have ligands that are smallnonpolar that can diffuse through the membrane Membrane receptors have largepolar ligands They cannot diffuse and must bind to transmembrane receptors They are for small polar molecules Receptors can also be categorized based on activity lon channel Protein Kinase Gprotein linked receptors GDP or GTP they both use guanine lon channel receptors also known as gated ion channels change their 3D shape when a ligand binds Ex The acetylcholine receptor is a ligand gated sodium channel it binds acetylcholine to open the channel and allows Na ions to diffuse into the cell Protein Kinase Receptor they activate the cytoplasmic domain that has catalytic activity Used to catalyze the following reaction ATP protein gt ADP phosphorylated phosphorylated means to introduce a molecule into protein Each kinase has a speci c target protein Ligands binding to G proteinlinked receptors expose a site that can bind to a G protein 3 subunits the G protein which is inserted into the lipid bilayer and the cytoplasmic surface G proteins bind 3 molecules The receptor the GDPGTP used for energy transfer an effector protein used to cause an effect in the cell Signal Activation can Lead to a cellular response that is mediated by a signal pathway Initiate a series of protein interactions that can then be ampli ed and distributed Be used as an intermediary between the receptor and cascade of responses these are usually secondary messengers Cytoplasmic enzymes can be activated by membranebound epinephrine in broken cells 0 Secondary messengers have been discovered to be cyclic AMP cAMP They amplify the signal by activating 1 targets Signal transduction pathways involve multiple steps one is that the enzymes can be activatedinhibited by other enzymes ExIn liver cells a cascade begins when epinephrine activates a Gprotein kinase pathway It then binds to a receptor activates the G protein and cAMP is produced and activates a different protein that phosphorylates the receptor Signal transduction ends after the cell responds The enzymes convert back and the balance between regulating and signal enzymes determine the cells response Cells can alter the enzyme balance in 2 ways synthesisbreakdown of the enzyme activationinhibition of the enzyme by other molecules Their function can also change due to environmental signals The opening of ion channels changes the electrical potential Ateration in gene expression Alteration of enzyme activities
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