MCDB 1B Notes
MCDB 1B Notes
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Molecular, Cellular And Developmental Biology
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This 27 page Class Notes was uploaded by Lauren Nagra on Wednesday September 3, 2014. The Class Notes belongs to a course at University of California Santa Barbara taught by a professor in Fall. Since its upload, it has received 76 views.
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Date Created: 09/03/14
MCDB 1B 2102014 Most life depends on WATER 0 We are like 60 Great solvent for cellular nutrients and waste Key concepts in nutritiontransport Variety of transport mechanisms 0 Macro vs microscopic pumps 0 Active vs passive contributions Structurefunction relationships of TISSUES CELL TYPES etc Regulatory mechanisms Circulatory systems Overview purpose structural organization Heart structurefunction Vessel structurefunction Blood compositionfunction Purpose of the circulatory system Transports nutrients respiratory gases hormones metabolic products etc 0 Travel THROUGHOUT BODY Temperature control 0 Large surface area gives more heat exchange 0 Ex jack rabbit ears sail Structural elements of CS Pump heart Conduits move fluid vessels Transport medium blood or hemolymph OPEN VS CLOSED ORGANIZATION o DifferenceCAPPILARY BEDS 0 CLOSED blood confined to vessels all the way through artery cap beds vessels 0 OPEN no cap beds goes in interstitial space you have HEMOLYMPH floods out there and gets recollected into vessels not continuously contained 0 CLOSED advantage faster flow with closed systemfaster exchange Selective you can determine what goes in and out of cap beds Vertebrate CS Fish have SINGLE circuit 0 Fishes heart has ONE ATRIUM ONE VENTRICLE ONE CIRCLE 0 Blood leaves heart and goes to some gas exchange organ 0 In this case that is going to be the gills 0 After its gone to the gills it hits a huge amount of resistance reducing pressure you have much lower pressure in systemic system than if it had come back to the heart More recent vertebrae circulatory systems 0 More circuits 0 2 pulmonary and systemic o pumonaryhas to do with lungs gas exchange organ 0 from heart through pulmonary circuit to heart comes back to heart goes out systemic system under high pressure 0 advantage of having TWO CIRCUITS systemic is under high pressure 0 increased number of heart chambers Better separation of blood flow to gas exchange organs and to rest of the body 0 Deoxygenated blood flows to gas exchange organ gillslungs oxygenated blood flows to rest of body systemic The Human Heart 2 Pumps in 1 4 chambers 2 atria and 2 ventricles blood enters atrium pumped out of ventricle right heart lungs left heart systemic valves prevent backflow left side works harder because it is doing SYSTEMIC thickermore muscular we pump greater than 300Lhour Cardiac cycle phases Contraction and relaxation systoe contraction phase diastoe reaxation phase time between those ventricle phasesSYSTOLE heart sounds made by heart valves opening and closing Blood pressure Can be measured using a sphygmomanometer and a stethoscope Squeezes shut your arteries 0 When they let out pressure it allows movement of bood 9 pushing past blood hear pusing9 eventually hear whooshing because it goes Which structure has blood with LOWEST oxygen concentration Pulmonary artery Effective pumping requires Sequential contraction of chambers Coordinated contraction of muscle cells within chamber depends on special features of cardiac muscle muscles striated because of regular alignment of actin and myosin filaments Contraction needs CALCIUM released at beginning and ATP for this to work so myosin and actin slide back and forth CALCIUM IS IMPORTANT Cardiac and skeletal differ in duration of contractions and transmission of action potential Sequential contraction Depends on specialized cells that initiate action potential and contraction Sinoatrial node SA node pacemaker activity no stimulus required Atrioventricular node delays start of ventricular contraction Bundle of his and purkinje fibers transmit action potential to ventricle walls Start out with signaling from sinoatrial node spreads across atreia contraction when it reaches AV node short delay bundle of hispurkinje spread the AP causing the ventricle to contract Action potentials in cardiac vs skeletal Very different in 0 Kinetics and ion channels involved Kinetics cardiac is 100x slower Different peaks because off diff ion channels Sinoatrial Node pacemaker Classes of unique ion channels 0 Spontaneously depolarize 0 funny current voltagegated Ca 2 channels produce action potential opening of K channels allows K to exit repolarization SA cells don39t contract When calcium is taken up then muscle contraction is over How are contractions of muscle cells coordinated within chambers Cardiac muscle cells are connected by gap junctions o Intercalated disks Electrical continuity allows rapid spread of action potential No gap junctions between atria and ventricles AAthat39s how you get sequential AND coordinated interaction EKGECG waves reflect specific electrical events P corresponds to depolarization and contraction of atria QRS correspond to depolarization of ventricles 0 Looking at calcium influx AAA T corresponds to relaxation and repolarization of ventricles o K going out AA Nervous system control of heart rate Sympathetic nerves release norepinephrine9increase heart rate 0 Norepine increases permeability of Na and Ca2 channels 0 Resting potential increases more quickly and AP are closer together quicker heart beat Parasympathetic release acetychoine9decrease pacemaker activity slow heart rate 0 Aceincreases permeability of K and decreases that of Ca2 channels 0 The resting potential rises more slowly and action potentials are further apart Controls by influencing resting potential of pacemaker cells Vessel structurefunction After blood gets pumped out of the heart it goes into vessels 5 types of vessels arteries carry blood away from heart arterioles control distribution to specific capillary beds capillaries site of exchange between blood and interstitial fluid venules return blood to veins veins return to blood to heart Vessel anatomy meets functional requirements Various types of reinforcements 0 Large arteriesreay wide diameter they are going to be delivering large amounts of blood 0 Veinsmuch smaller can expand greatly o Capillaries are so narrow that you really only have single file for blood cells going through there Pressure and velocity change a lot 0 Pressurehigh when it is just leaving the heart and velocity is high 0 At capillaries total area becomes enormous Because it spread out through many capillaries pressure and velocity goes way down 0 Venulesveins pressure is still low velocity starts to pick up II MCDB 1B 2142014 03092014 1048 AM Blood flow after heart arteries resistance vesses9vein 70 of blood Arteries and arterioles have Elastic fibers enabling them to withstand high pressures Smooth muscle cells allowing them to contract and expand alter their resistance and thus blood flow Veins have VALVES to prevent backflow of blood ARTERIES 5 LAYERS VEINS 3 LAYRES Atherosclerosis hardening of arteries Plaque fucks shit up Arterioles control distribution to capillary beds Precapillary sphincters alter diameterresistance to blood flow subject to both local and systemic control Local control responsive to local conditions Such as gases O2 and CO2 concentrations concentration of metabolites All of that info AA provides info to cap bed on what to do for blood flow First autoregulation local Central blood pressure when it falls systemic starts Systemic control of blood pressure Responses to changes in central blood pressure and composition mediated by nervous system and hormonal signals Sympathetic nerves release norepinephrine9smooth muscles contract constrict vessels increase BP decrease blood flow Parasympathetic nerves release acetylcholine relax smooth muscle increase flow decrease BP Chemoreceptors determine which one you are using What controls direction and identity of material movement between blood and interstitial fluid Direction of fluid movement controlled by balance between blood pressure and osmotic pressure based on pressure difference of blood extra fluid returned to blood by lymphatic system identity of molecules moving depends on conc gradients permeability of capillary walls in specific tissue availability of pores endocytosis in some tissues 3 diff cap walls cap walls are 1 cell layer think most have small pores making them leaky fenestrated discontinuous they are all permeable to 02 CO2 glucose lactate and small ions lack of pores in brain caps blood brain barrier only lipid soluble materials can cross digestive and excretory systems are much less selective Returning blood and fluid to the heart Veins have a high capacity for storing blood because walls are very expandable Lymphatic vessels return fluid to major vein returning to the heart Skeletal muscle contractions and gravity help veins and lymphatic vessels carry blood and fluid back to the heart Valves prevent backflow Blood CompositionFunction Pasma55 o Focusing on red blood cell Challenge of CS Transport gases efficiently via liquid medium Despite low solubility of gas in liquid Ways to fix 0 Efficient loadingunloading gas in lungs alveoli Blood movies rapidly through capillaries surrounding alveoli Movement maintains O2 and CO2 conc gradients promoting diffusion 0 Increase good oxygen carriers Small biconcave high SAvolume aids diffusion Anaerobic metabolism no 02 consumed Contain hemoglobin protein binds 02 oxygen carrier Hemoglobin binds 02 directly and cooperatively increases 02 capacity of blood 60x Oxygen binding capacity of hemoglobin varies under different conditions 2 High metabolic rate decreases pH drives greater 02 release 2 Low 02 increases RBC glycolysis increased BPG Oxygen binding adaptations of Hgb 2 Live at low P029 increase binding affinity 2 Fetal Hb has higher affinity than maternal o ANOTHER HB VARIANT sickle cell Deoxygenated Hb S forms large polymers that distort and damage RBCs and disrupt flow through capillaries Hb S confers resistance to malaria infeceted cells sickle and are destroyed Removal of CO2 from tissues 0 Action of carbonic anhydrase maintains CO2 gradient from cells high to plasma low 0 Some CO2 complexes with deoxygenated Hb O MCDB 2192013 03092014 1048 AM Macroscopic pumps movement depends on action potentias which ion channels are important for this Gas exchange promoted by concentration gradients maintained by rapid blood flow Proteins and enzymes convert gases to more soluble form Flow rate subject to local and systemic hormone control Clicker q The amount of oxygen carried by hemoglobin depends on partial pressure of oxygen in the blood Hemoglobin in active muscles 0 Readily unloads oxygen NEW SECTION Salt and Water Balance Excretory systems 0 Purpose filtration and maintain osmotic balance 0 Kidneys Structurefunction of parts Regulation Key concepts 0 Characteristics of cells engaged in absorption high SAvol o Countercurrent exchange 0 Mechanism for altering permeability to water Purpose of excretory systems Blood carries nutrients and waste requires filtration to remove garbage Maintain osmotic balance of cells to prevent extreme volume changes 0 Can depend on where you live Requirements and mechs vary depend on animals environment 0 Live in fresh water need to excrete water conserve solute 0 Live in terrestrialdry enviro need to conserve water excrete solutes Waster products of metabolism Nitrogenous waste must be excreted andor detoxified Fish gis Humans urea used for excretion Some animals that have eggs shells uric acid insoluble Excretory systems Functions 0 Filtration of body fluids 0 Osmoregulation Structures 0 Invertebrates have diverse excretory systems 0 Vertebrates have kidneys as excretory systems The nephron is the functional unit of the vertebrate kidney 2 components vascular leaves heart comes back to heart 0 nephron tubules 3 parts of nephron o 1 Renal corpusce glomerulus cap bed and bowman s capsule surrounding nephron partsite of filtration o 2 Renal tubuesite of tubular secretion and absorption surrounded by capillaries o 3 Collecting ductsite of urine processing eg concentration or dilution 2 capillary beds in series 0 Have arterioles leading into them 0 The one leaving is called the efferent arteriole one coming in is afferent arteriole The concentrating ability of kidney depends on anatomy Entry and exit of blood on concave side Nephrons 1 millionkidney regularly arranged within kidney Nephron arrangement within kidney Glomeruli in cortex Renal tubules loop through medulla Collecting ducts start at cortex pass through medulla empty into ureter Animals that live in REALLY dry places extra room for really long loops of hanley ability to concentrate water Renal corpuscle structurefunction Glomeruli are highly permeable capillary beds Bowman39s capsule cells surrounded by glomeruli Podocytes are surface cells of the bowman s capsule o Surround surface of glomerular capillary Blood pressure forces water and small molecules from glomerulus into bowman s capsule Cells and large molecules are retained in blood Renal tubule structurefunction Nephron tubules may loop across the kidney Each tubule has four specialized zones 0 Proximal convoluted tubule 0 Loop of henle o Distal convoluted tubule 0 Collecting duct Cell structure in the different zones reflects function Structure determines function Structurefunction of proximal convoluted tubule cells Func on Main place you are absorbing NaC glucose and aa s water follows by osmosis pH regulation by secretion of H reabsorption of HCO3 bicarbonate buffer system humans maintain blood pH of 735745 bicarbonate HCO3 buffer in our blood pH regulation by bicarbonate buffer system reversible reaction protons actively secreted into lumen inside tubule increases proton concentration there which pushes carbonic acid to be made leading to more co2 made co2 diffuses back into tubule cells pushing another reaction in a direction to make MORE bicarbonate which is going to move to interstitial tubes to be taken up by tubules protons tubules INCREASES blood pH lungs CO2 H20 lt gt H2CO3lt gtH HCO3 kidneys secretion of NH3 and assorted poisons materials removed from tubules returned to venous blood via uptake in peritubular capillaries Loop of Henle is a counter current multiplier Function creates concentration gradient in medulla by countercurrent exchange Another example of countercurrent exchange o Anti parae flow creates steeper parallel flow because conc gradients maintained throughout area of exchange Structurefunction of loop of henle Descending limb relatively unspecialized highly permeable to water but no ions Thin ascending limb permeable to NaCl Thick ascending limb actively secretes NaC low water permeability Osmotic water movement limited to permeable cells Osmolarity of lumen increases transiently in medulla Water will continue to move out as long as there is a higher conc externally Establishes external conc gradient across medulla Structurefunction of collecting duct Permeable to water but not ions Slightly permeable to urea at bottom Passing thru increasing osmolarity of medulla created by loops of henle Water leaves collecting duct by osmosis9urine becomes more concentrated Degree of conc depends on magnitude of gradient Descending reease water ascending release salt last final conc final COHC Clicker Q The sole mechanism for water reabsorption by the renal tubules o osmosis MCDB 2212014 03092014 1048 AM Summary of specialized zones of renal tubules proximal convoluted tubule major site of salt nutrient and water reabsorption pH regulation secretion of wastes loop of henle creates external concentration gradient in medulla by countercurrent exchange distal convoluted tubule NaCl and water reabsorption pH regulation fine tuning of ions collecting duct concentrates urine as water lost by as osmosis degree of concentration depends on magnitude of gradient from loop of henle How much fluid do we filter and reabsorb each day Adult human kidneys o Receive1100 2000 liters bloodday o Fiter180 litersday o Urinate only 23 liters 0 9899 of volume reabsorbed in proximal tubule descending limb of loop of henle and collecting duct 0 massive water flux across these cell layers What is mechanism of massive water flux What are options for movement across membranes active or passive o Diffusion through bilayer or channel Good correlation between how soluble something is in lipid and how easily it can get through membrane water way off this line 0 Liquid solubility of water not sufficient to explain its membrane permeability Aquaporins are a family of water channels 0 Existence proposed 50 years ago Possibilities simple diffusion and channel mediated WATER CHANNELSAQUAPORINS Integral membrane proteins that form water seective channels gt 13 family members in mammals gt30 in Arabidopsis expressed in tissuesmembranes with HIGH H20 permeability peter agre received 2003 nobel prize OOOO OOO Injected pops because water is flowing in by osmosis lots of water flows in Aquaporins in kidney function 0 Abundant in structures with high water permeability Proximal convoluted tubule Descending limb of loop of henle Collecting duct 0 Diabetes insipidius lots of dilute urine can result from mutation in an aquaporin family member Regulation of filtration o Filtration requires adequate blood pressure 0 FILTRATION SEPERATES NUTRIENTS FROM WASTE 0 Regulatory mechanisms maintain a constant high glomerular filtration rate 0 Both local and systemic controls Mechanism to maintain renal blood pressure by LOCAL autoregulation If systemic pressure decreases afferent incoming renal arterioles dilate to maintain flow through capillaries 0 allows more blood Systemic regulation of blood pressure Renin angiotensinaldosterone system 0 Response to decreased blood volume and BP 0 Increase local and systemic BP by effects on vessels and fluid intake RAA system angiotensin increases local and systemic BP by effects on vessels and fluid intake 0 Efferent renal arteriole constricts 0 Peripheral blood vessels constrict o Aldosterone stimulates Na reabsorption o Stimulate thirst Systemic regulation of blood pressure Blood osmality 0 Rise in blood osmolarity Reninprotease dilute tubule fluid Renin takes angiotensinogen angiotensin 1 Angiotensin 19 angiotensin Angiotensin o Stimulates thirst o Stimulates adrenal cortex to release aldosterone o Stimulates peripheral vasoconstriction Aldosterone increases Na2 REABSORPTION ADH system Blood osmolality and blood pressure Not enough fuidreease Increase water reabsorption to concentrate urine Increases water permeability of collecting duct via effects on aquaporin content High osmolarity and decrease in blood pressureADH release 0 Not enough fluid in blood 0 Solution increase water absorbed o Modifies aquaporin content in collecting duct up permeability Increases 20x win 510 mins Experiment ratscollecting ductswith and wo ADH 0 Nice correlation between where aquaporins are and where there is permeability Systemic regulation of blood pressure Atrial natriuretic peptide ANP 0 Released in response to atrial stretch o Decreases salt and water uptake in kidneys o Inhibits the synthesis and release of aldosterone o Inhibits renin production and ADH release Low blood pressure high osmolarity o Constrict efferent arterioles and peripheral vessels increase salt uptake thirst water uptake using ADH and reninangioaldo High blood pressure in heart 0 Decrease salt and water uptake in kidney with ANP Clicker Q if afferent arteriole that supplies blood to the glomerulus become dialated THE GLOMERULAR FILTRATION RATE INCREASES SUMMARY OF KIDNEYS SLIDE You are regulating solute movement water just follows INTRODUCTION TO PLANTS Plants give you Food fiber fuel pharmaceuticals fragrances flowers Co2 sink Stable food supply provided by agriculture sustains enormous population growth Advances in medicine greatly increase life expectancy Are we sustainable Plant growth limited by drought Driest pacesarge and hungry populationpolitical instability CALINUMBER 1 WATER CONSUMER Plant scientists can contribute to the alleviation of hunger By developing plants that o Are drought or stress tolerant o Require less fertilizer or water 0 Are resistant to pathogens 0 Are more nutritious Plants provide more than food Drugs fiber energy sources Plant biology through the centuries Phase 1 pre civ91600s descriptive Phase 2 1700s to early 1990s experimental Phase 3 late 90s present genomics revolution is providing avalanche of information How plants relate PHASE 1 First cells species pants PHASE 2 Fluid transport Photosynthetic O2 production Genetics First virus PHASE 3 Genes have been cataloged Genome sequencing Transcriptome RNA proteome PROTEIN metabolome 0 How things work w ALL INFO Unity of biology Common ancestor many basic mechanism Conserved genes and functions Studying model system Comparison of some eukaryotic genomes We have lots of repetitive genes but relatively same number of genes Common themes from genome comparisons Duplicate genesredundancy same function by more than one gene can back up each other Genes involved in basic cellular functions conserved across kingdoms Many regulatory genes conserved within kingdoms Some genes are more represented in plants vs animals reflect specialized metabolism or communication 0 Plant enriched cell wall synth photosynthetic secondary metabolism some regulators 0 Animal enriched some classes of signaling molecules Overview of Plant Architecture PLANT CELL Different cell wall chloroplast Formation of new cell wall when cell DIVIDES new wall built Vesicles coalesce at cell plate Vesicles fuse to form middle lamella with some gaps 2 Middle lamella put down first 0 Daughter cells secrete wall material at PM surface 0 Results in age gradient within wall Constraints imposed by cell wall 0 Cell position fixed no cell migration 0 Cell position reflects lineage body is age gradient tip growth 0 O o Permits permanent connections to adjacent cells plasmodemata MCDB 2242014 Cell Wall 03092014 1048 AM Cell and body of pant age gradient reflects cell position and Hneage Permits permanent connections to adjacent cells plasmodesmata Growth depends on turgor hydrostatic pressure to stretch walls plasmodesmata permanent connections between adjacentsibling cells gating alters effective pore size changes connectivity during plant39s life that effective change can change sympast interior space of cells connected cytoplasm plasmodesmatal connections are maintained in pit fields of secondary walls Composition of cell wall 2530 cellulose major structural component 4055 other polysaccharides mix 115 o protein fully hydrated extracellular matrix walls critical for structure but also site of cellcell contant and communication middle lamellaoldest part of wall newst partbottom plasma membrane hemicelluloseimportant for crosslinking ceuoseinear glucose polymer lots of H bonding potential organization of cellulose and other polysaccharadies in wall matrix cellulose microfibrilson outside Composed of 30250 linear molecules Hbonded together Length varies from 200025000 glc residues per molecule Crosslinked by other polysaccharides Plant cells can elongate up to 200x Elongationexpansion requires turgor pressure up to 10 atm and wall loosening Major increase in cell volume occurs in vacuole not cytoplasm Direction of expansion s always perpendicular to cellulose microfibrils o The direction of microfibrils becomes important Orientation of cellulose deposition determines orientation of growth Orientation of cellulose microfibrils in elongation in walls Cell expansion is accompanied by new cell wall synthesis Old microfibrils shift to more vertical orientation as cell elongates Deposition of new microfibrils at cell surface continues perpendicular to long axis of cell maintans orientation of expansion New are horizontal they begin to slip as they get older and turn diagonal vertical new is always horizontal tho Cellulose is synthesized on the cell surface by enzyme complexes in the plasma membrane associated with cortical microtubules Plant secondary walls Highly regular array of cellulose Microfibrils often10x longer than primary walls very rigid No further expansion possible Include variety of specialized polymers Summary of plant cell wall effects on growth Cell wall imposes many constraints on growth because cell position fixed Growth requires turgor pressure to stretch wall Cellulose is major structural component of wall orientation of microfibrils determines orientation of cell elongation and therefore overall plant shape Secondary wall too rigid to permit further expansion Cell wall creates two major compartments of plant body apopplast and symplast basic plant body plan growth is indeterminate and repetitive plants have three major tissue types dermal vascular and ground 0 present in all organs of plant 0 relative position of vascular tissue changes 0 vascular core of root stee meristems are the ultimate source of all plant tissues meristemsundifferentiated cells at apices and assorted patches within plant body apical meristems primary growth lateral meristems secondary growth primary growth secondary growth corkprotective layer vascuarnew vascular tissue xyleon and phloem vascular cambium thickens stems and roots spring has wider vessels because more water is being carried 0 seasonal differences in water availability result in different diameter vessels visible as annual rings Summary of plant architecture 3 major tissue types dermal vascular and ground meristems are ultimate source of all tissues different meristems responsible for primary vs secondary growth repetitive formation of few major organ types roots stems leaves buds flowers variety of specialized cell types within each tissue meristemsbuds Vascular system water and mineral movement site of movement xylem driving force for movementwater potential gradient path of water movementwater potential gradient path of water movement through plant Xylem is a major site of water and mineral movement Two major cell types Tracheids and vessel elements 0 Trachieds more ancient 0 Many of vessel elements cells are dead no cytoplasm only apoplastic movement How does water move to tops of tall plants No macroscopic pumps like heart Like a straw leaves suck water through plant body from bottom Driving force for that is water potential gradients What is water potential Tendency of solution to take up water from pure water across a membrane osmosisosmotic movement Total water potentiapotentia solute potential Pressure Pure water has water potentia0 Can be positive or negative neg under tension Water always moves to region of lower pressure Measured in megapascals Water movement Xylem connects water in soil potential near 0 air surrounding leaves potential much lower than zero neg Evaporation draws water out of leaf mesophyll Cohesion of water via H bonding maintains continuous column of water through plant transpiration stream Water moves under tension cuz of evaporation Movement is unidirectional from 0 9 extremely neg even tho its opposite to gravity Xylem sap is under tension usually Put in pressure bomb Sap gets drawn back inside plant by tension Put plant into chamber of pressure bomb put pressure and get sap to come out amount of pressure appiedamount of tension When humidity is high root pressure results in guttation from positive pressure MCDB 2262014 03092014 1048 AM Regulation of Flow rate entry and exit from plant If xylem sap is under tension up to 25 atm why don39t cells collapse Because xylem cells have highly reinforced secondary walls All that39s left is cell wall Apoplastic movement through xylem it is through cells but they are dead so it is EXTRAceuar If xylem sap is under tension why doesn39t water column break and airlock system Bubbles can happen sometimes they are trapped in elements when formed 0 Caviated vessel element 0 Gets trapped in that cell Flow is maintained by network of vessels connected by pits 0 Despite bubbles Rate of fluid movement through xylem is controlled by Temperature and evaporation rate ENVIRONMENTAL FACTORS Vessel width 0 25200 microns in diameter pits in xyem aong edge of pitmembrane area that can swell or decrease depending on cell content sap goes from one cell to adjacent cell 0 pure water microchannel thin o KCI microchannel thick more rapid movement diameter of pit membrane microchannels can be altered by salt content of sap regulated by plant Experiment K affects the xylem flow rate If having water or K solution would flow more quickly through xylem Measuring uptake assaying by balance Relative flow rate water stays constant If you add K solution big spike where flow rate goes up return back to water Flow rate goes back down 0 Salt concentration can really modify the flow rate CONCLUSION K INCREASES THE RATE OF FLOW IN THE XYLEM TENSION in xylem fluid CAUSED by transpiration at the leaf surface Path of water and mineral entry into root epidermal layer root hairs increase surface area for absorption movement through cortex may be apo or symplastic o APO extracellular space goes in between cells not actually in them 0 Symplastic into interior part of cells can go through all the adjacent cells like plasmadomata Entry to stele requires symplastic movement across endodermis Casparian strips force symplastic movement across endodermis CORTEXout Casparian strip around endodermis Gray is waxy gasket preventing apoplastic movement Forces everything to go into SYMPLAST at that step making plant selective it actually has to take stuff up so it chooses what to take Uptake requires ENERGY Where does that energy come from ATP hydrolysis Proton pump pumps protons from inside to outside pH gradient more protons on the inside than the outside 0 lower pH 55 OUTSIDE charge gradient positively charge outside neg inside 0 substantial resting potential 120 mV 0 drives countertransport of cations o symport couples uptake of anions and H driven by pH gradient protons moving down gradient drag anions with them fluid goes to stele most fluid returns to apoplast in pericycle or xylem parenchyma wide xylem cells In order to get back to apoplast o TRANSFER CELLS high surface area and many mitochondria 0 Trying to move LOTS of mitochondria across cell membrane What happens to water after entry into stele gt900o flows through and out of plant 0 majority is apopastic Rest moves osmotically into vacuoles of growing cells Cells adjust vacuolar solute to drive osmotic water uptake Growing areas have high water flux across vacuolar membranes 0 Aquaporins have like 30 STOMATA onoff switch for transpiration stream Surrounded by guard cells 0 Whether they are open or closed influences intake Openingclosing depends on guard cell structure and osmotically driver TURGOR CHANGES Structure they have these radially oriented reinforcements along wall 300400 mM K flux between guard and surrounding epidermal cells accompanied by anion and water flux as volume goes up they open creating pore pore makes evaporation happen water and ion flow allow pore to close Ion and water flux via channels and apoplast low density of plasmodesmata prevents short circuiting of ionic flux and turgor change Reversible change in cell volume Stomatal aperature controls balance between access to CO2 for photosynthesis and water loss via transpiration Aperature regulated by 0 Light or low CO2 promote opening 0 High CO2 or water stress signaled by ABA promote closure 0 Signaling that is involved here involves many other intermediates described in other systems Ca2 IP3 cADPR reactive oxygen species NO G proteins phosphorylation cascades Although opening and closing involve net ion movement in opp directions they are not simple reversal of same process 0 There are different channels that do stuff and different channeling going on What happens if a plant can39t regulate stomata Left regular right aba deficient ABA deficient mutants cannot close their stomata end up short and wilty partly because they cannot retain water needed for turgor STOMATAL APERATURE REGULATED BY LIGHT AND ABA Do plants have action potentials Action potentiassudden transient major changes in membrane potential Membrane potentiacharge difference between inside and outside of cell due to asymmetric distribution of ions Uptake of K reduces charge inside cell depolarization K efflux or anion uptake increases Plants do have sudden transient major changes in membrane potential Faster ones are in same time scale as cardiac Not as fast as neural What minerals do plants need and why do we need them Macronutrients need at least 1 gkg of dry weight Micronutrients need less than 100 mgkg of dry weight Roles may be structural catalytic signaling ion balance 0 Soil fertility is partly a reflection of how many mineral nutrients are available Lots of microbial and fungal stuff in soil that help plants in terms of nutrition Carbohydrate movement Site and direction of movement Driving force for movementpressure flow Fed a leaf with radioactive CO2 will make radioactive glucose Pulse labeling allows some time for transport you can see where it ends up you find that it doesn39t go every where Site where the radioactivity goes is referred to as SINK TISSUE because stuff is moving into that cell Actively photosynthetic places SOURCE TISSUE Transport is multidirectional no macroscopic pumps Dual osmometer mode A source sitting in water water will move in osmotically But in sink side there isn39t NET FLOW from source sink
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