Week 4 LS2 Notes
Week 4 LS2 Notes Life Sciences 2
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This 6 page Class Notes was uploaded by Jenna Kovsky on Sunday October 25, 2015. The Class Notes belongs to Life Sciences 2 at University of California - Los Angeles taught by Dr. Cooper/Dr. Esdin in Fall 2015. Since its upload, it has received 21 views. For similar materials see Cells, Tissues, and Organs in Biology at University of California - Los Angeles.
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Date Created: 10/25/15
10l19l15 Lecture 10 lecolvs amp Cell Respiration cont and Cell Communication END OF FRIDAY S LECTURE o Glycolysis net gain 2 ATP as well as some NADH O O O O 0 does not require oxygen Acetyl CoACH3COCoA glucose enters the cell via facilitated diffusion gets converted into pyruvate 2 ATP Pyruvate enters mitochondria matrix and the next product is Acetyl 00A 0 brown fat type of adipose tissue present in newborn babies and hibernating animals contains lots of mitochondria used to generate heat 0 O mitochondria contain thermogenin protein that lets protons H leak back through mitochondrial membrane into the matrix energy of the proton is released as heat instead of making ATP 0 GTP is energetically equivalent to ATP made by substratelevel phosphorylation during the Krebs cycle 0 Fermentation occurs anaerobically wo oxygen 0 O O certain yeasts make alcohol conversion of pyruvate to lactate in anaerobic muscle build of of lactic acid in working skeletal muscle is what gives you cramps when you exercise mitochondria need oxygen as an electron acceptor not enough oxygengt I NADH and FADH2 levels increase no final electron acceptor I Krebs cycle stops no NADH or FADH2 to fuel it I pyruvate levels increase I lactate lactic acid increases 0 causes acidic environment which causes pain and reduces contraction of the muscle lactate dehydrogenase can drive reaction in reversible manner uses NADH from glycolysis to convert pyruvate into lactic acid lactate gluconeogenesis making glucose from noncarbohydrate precursors eg lactate I some lactic acid can go to liver to get reconverted into pyruvic acid and ultimately into glucose 0 Alcoholic Fermentation anaerobic conversion of pyruvate into Acetaldehyde in yeasts o Lipids triglycerides can by hydrolyzed into fatty acids 0 glycerol enters glycolysis o Eukaryotes O 0 outside of mitochondria I glycolysis I fermentation inside the mitochondria I inner membrane o respiratory chain I matrix 0 citric acid cycle 0 pyruvate oxidation 0 Prokaryotes o cytoplasm I glycolysis I fermentation I citric acid cycle 0 on plasma membrane I pyruvate oxidation I respiratory chain END OF MIDTERM 1 MATERIAL CELL COMMUNICATION o Endocrine System composed of endocrine glands throughout the body generally regulates activities that require duration not speed 0 one of the main regulatory systems in the body along with the nervous system c Hormone longrange chemical messenger of the endocrine system that is synthesized in a gland and released into the bloodstream then works on particular target cells to bring about some characteristic physiological response 0 target cells must have the appropriate receptors 0 eg insulin made in pancreatic beta cells and released into blood stream by exocytosis 0 Local Mediators I eg Histamine injurygtarea gets red released in response to injury from mast cells makes small blood vessels capillaries more permeable than normal 0 larger capillaries let white blood cells WBC infiltrate the injured area to take care of any invading pathogens like bacteria I eg Growth Factors proteins that promote growth via cell division 0 1st discoveredEpidermal Growth Factor EGF o 3040 different ones specific for different tissues 0 Types of Hormones o peptidesproteins small numbers of amino acids linked together most hormones including the ones secreted by hypothalamus anterior and posterior pituitary pancreas and parathyroid o amines derived from tyrosine amino acid include hormones secreted by thyroid gland and adrenal medulla inner region of adrenal gland I catecholamines adrenomedullary hormones eg epinephrineadrenaline and norepinephrinenoradrenaline o steroid neutral lipids derived from cholesterol include hormones from adrenal cortex outer region of gland ovaries and testes steroid and thyroid hormones are lipophilic lipid soluble o Mechanisms of Hormones o hormones alter intracellular protein activity 0 bind w specific target cell receptors starting chain of events in target cell 0 based on receptor location two groups I plasma membrane receptors I intracellular receptors 102115 Lecture 11 Cell Communication cont MIDTERM REVIEW 0 Chemiosmosis Experiment 2 0 using artificial system 0 phospholipid spontaneously form vesicles in vivo 0 Bacteriorhodopsin lightdriven proton pump I from halobacteria which lives in extreme environments and pumps protons out of its plasma membrane I contains retinal which changes the shape of the BR protein when light is directed to it allowing H to flow through the protein 0 purify bacteriorhodopsin and insert it into the phospholipid vesicle but oriented the opposite direction from how it would be normally 0 oriented so that it pumps protons into the vesicle when light is shone onto it making the interior acidic o If you add purified ATP synthase oriented with rotating headgroup facing outwards from vesicle the protons flow out and the headgroup uses the energy of the proton gradient to rotate to bring ADP and Pi together to form ATP 0 Motor Proteins 0 have feet that can move using the energy of ATP hydrolysis and walk along microtubules CELL COMMUNICATION o Circulating hormone gland releases hormones into bloodstream which travel to target cells 0 watersolublepolar hormones peptides proteins catecholamines are transported dissolved in the plasma and bind to a receptor on the target cell s surface to relay the information o Iipophilicnonpolar hormones steroids are transported largely bound to plasma proteins and diffuse through the membrane to bind to a receptor inside the cytoplasm of the cell c A hormone acting on its target cell receptor produces a characteristic response in a target cell which is different for different hormones and also for different target cells even when responding to the same hormone o epinephrine an adrenal medullary catecholamine causes contraction of vascular smooth muscle relaxation of respiratory airway smooth muscle breakdown of liver glycogen increased rate and force of contraction of heart o Paradigms for Hormone Action 0 hormones alter the activity of proteins in the cell by a mechanism such as most hydrophilic hormones binding to a cell surface receptor produce a second messenger in the target cell some hydrophilic hormones after binding to receptor on cell surface open or close some ion channels to alter cell permeability lipophilic hormones through binding to intracellular receptors activate specific genes leading to the formation of new intracellular proteins 0 Types of cell surface receptor 0 ligandgated ion channels eg acetylcholine receptor when 2 ACh bind to a receptor on a skeletal muscle fiber receptor allows Na into the cell when the ligand just means a small molecule or ligands are bound to the ion channel it opens to allow ions to travel through which causes muscle contraction o Gproteinlinked receptors Guanyl nucleotide binding proteins G proteins act as molecular switches On when GTP is bound Off when GDP is bound contain builtin timer that is an intrinsic GTPase which splits GTP to GDP G proteins are heterotrimeric have 3 different subunits alpha beta and gamma 0 alpha subunit can bind to GTP hormone binding to receptor activates G protein and GTP replaces GDP activated G protein dissociates alpha subunit breaks off and goes to bind to some kind of Effector protein and GTP gets converted to GTP alpha subunit reassociates with its beta and gamma parts 0 enzymelinked receptors eg insulin receptor 102315 hormone binds to its receptor on target cell receptors is made of two subunits alpha and beta insulin binds to alpha subunit beta subunit spans the cell membrane 2 receptors form a dimer 3 amino acids can accept phosphate groups tyrosine serine and threonine 0 phosphate group is large and negatively charged can change the shape of the phosphorylated protein Lecture 12 Cell Communication cont 0 Gproteinlinked receptors span the membrane seven times 0 Cyclic AMP a second messenger that is formed from ATP by adenylyl cyclase an enzyme that is activated by a Gprotein 0 important signalling molecule inside cells 0 activates a kinase cascade which releases glucose from glycogen glycogenolytic cascade I kinase enzyme that split ATP into ADP and transfer the resulting Phosphate group onto proteins onto a particular sidechain which changes the properties of the protein at the same time glycogen synthesis is inhibited the kinase cascade amplifies the epinephrine signal release of glucose is a key part of the fight or flight response to epinephrine which works on the liver to break down stored glycogen o basically cAMP leads to the phosphorylation of specific proteins 0 most of cAMP effects are mediated via cAMP dependent protein kinase PKA o Glycogenolytic cascade refers to the breakdown of glycogen in the liver 0 cascade bc it s a series of events 0 epinephrine binds to receptor on cell membrane 0 when the gprotein makes receptor complex it releases GDP and adds GTP and then activates the adenylyl cyclase which uses ATP to activate cAMP o cAMP begins the kinase cascade 0 Why so many steps amplification 0 each molecule of epinephrine binding can release many many glucose molecules into the bloodstream o The lnositol Lipid Signaling Pathway o Phosphatidylinositol 45 bisphosphate is cleaved by phospholipase C following receptor activation of a G protein to form 2 intracellular messengers I diacylglycerol activates protein kinase C I inositol trisphosphate IP3 release calcium from the endoplasmic reticulum 0 Calcium as an intracellular messenger 0 concentration of Ca2 is kept low 01 micromolar by active transport out of cell and into ER many different signals can open Calcium channels once calcium channels open calcium concentration rises up to 100x resting concentration Calcium ions bind to a protein called calmodulin which activates Fura 2 is a fluorescent calcium indicator used to see the calcium concentration of cells when the color changes it means the calcium levels have changed looking at dynamic changes in cells through fluorescent microscopy 0 Elements of Cell Signaling o signaling cell 0 signaling molecule wide variety growth factor pheromones hormones gases etc O O 0 receptor cell surface or intracellular target cell response depends on the cell Examples of Signal Transduction Pathways nitric oxide gas NO causes vascular smooth muscle relaxation and vasodilation of blood vessels important in blood pressure regulation reduces blood pressure hypotensive linked to effects of the neurotransmitter acetylcholine leads to influx of calcium in the endothelial cell that lines the blood vessel Nicotinic acetylcholine receptor opened by the drug nicotine by a gprotein it releases IP3 binding to receptor that increase calcium in the cell gases can readily cross plasma membranes guanylyl cyclase converts GTP to cGMP smooth muscle relaxes causing more blood flow vasodilation Ras mutations in Cancer Ras monomeric G protein that behaves similarly to the alpha subunit of heterotrimeric G protein involved in the signaling cascade of growth factors to the nucleus mutation in ras occur in many human tumors esp pancreas colon and bladder in a normal cell ras is inactive when GDP is bound when GTP is bound Ras stimulates cell division there is an intrinsic GTPase that inactivates Ras brief stimulation of cell division 0 normal ras termed a protooncogene in a cancer cell c Ras is mutated GTPase timer that decides how long Ras stays active activity can be inhibited 0 cell division overstimulated o The mutated ras is called an oncogene tumorpromoting gene sense of smell occurs via odorant molecules activating a G protein and causing cAMP to open an ion channel this generates an action potential which travels along the olfactory nerve to the brain does not work through PKA instead cAMP binds directly to a ligandgated ion channel
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