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Plant physiology

by: Anahit Ghaltaghchyan
Anahit Ghaltaghchyan
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This 21 page Class Notes was uploaded by Anahit Ghaltaghchyan on Friday February 26, 2016. The Class Notes belongs to MCDB 1B at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by Finkelstein in Winter 2016. Since its upload, it has received 27 views. For similar materials see MCDB 1B in Microbiology at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months.


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Date Created: 02/26/16
plant physiology 02/17/2016 ▯ ▯ 60-70% of our blood is in our veins ▯ 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 ▯ ▯ Capillaries- about a single blood cell can fit through at a time. Very thick wall in the arteries compared to veins ▯ ▯ Atherosclerosis- hardening of the arteries, buildup of plaque ▯ Thrombus(clots) can form ▯ ▯ Arterioles control distribution to capillary beds: precapillary sphincters alter diameter/resistance to blood flow subject to both local and systemic controls ▯ Muscle fibers wrapped around the arteriole, can restrict flow to capillary bed which makes the bed close ▯ ▯ Local and systemic regulation of blood pressure  Local accumulation of metabolic wasted. Widening of the vessels to get blood to capillary beds. But as you open up a lot of capillary beds, the overall arterial pressure tends to fall. Needs a systemic response to respond to such changes. Found in different parts of the body (such as stretch receptors), kidney etc. send to hormonal signals with a net affect of increasing water reabsorption or stimulate thirst, leading to rise in arterial pressure  Feedback mechanism^^^   Arterial pressure can also be regulated by the nervous system by acetylcholine in the PNS or epinephrine from Sympathetic. o Responses to changes in the central blood pressure and composition mediated by NS and hormonal signals  Sympathetic releasing epinephrine.. increases BP, decreases blood flow(except skeletal system)  Parasympathetic- release acetylcholine that will relax the smooth muscle, increases flow, decreases blood pressure ▯ ▯ What controls direction and identity of material movement between blood and interstitial fluid?  Direction- control by balance between blood pressure and osmotic pressure starlings pressure  Hydrostatic pressure inside those capillaries is greater than the osmotic pressure. Net outward force in arterial end  Vein end have the opposite  Net fluid loss across the capillary bed due to more fluid leaving in the arterial end  Gets back into the blood stream by the lymphatic system  Identity of molecules moving depends on concentration gradients, permeability and_________ ▯ Tissue specific differences in selectivity  Continuous  Fenestration  Discontinuation  `capillary walls are 1 cell layer thick  most tissues except the brain have small pores in these walls that make them leaky  capillaries of all tissues are permeable to o2 co2 glucose lactate and small ions  lack of pores in most brain capillaries is what causes the blood brain barrier, only lipid soluble materials can get across  digestive and excretory system much less selective ▯ returning blood and fluid of heart  veins have a high capacity for storing blood because walls are very expandable  lymphatic vessels return to fluid to major veins returning to the heart  skeletal muscle contractions, breathing, and gravity help veins and lymphatic vessels carry blood and fluid back to the heart  valves prevent back flow  gas exchange at the alveoli  HIGH surface area of about 70 m^2  Blood moves rapidly through capillaries surrounding alveoli  Movement maintains o2 and co2 concentration gradients promoting diffusion . co2 in blood is much higher in blood compared to alveoli. Moves down concentration gradient ▯ ▯ Red blood cells are efficient oxygen carriers  Small biconcave, high surface area/volume, aids diffusion  Anaerobic metabolism  Contains hemoglobin ▯ Blood composition/function  Transport gases via liquid medium, despite low solubility of gas in liquid ▯ Lower pH leads to more oxygen being released ▯ ▯ Oxygen binding adaptation if hemoglobin ▯ Live at low pressures of o2. Increases binding affinity ▯ Fetal hemoglobin has higher affinity than maternal. Higher affinity shifts towards the y axis/ steeper ▯ Myoglobin has an exponential type graph ▯ ▯ RBC production stimulated by low oxygen content in tissues ▯ Flow chart thing with kidneys ▯ ▯ Recombinant erythropoietin and related products produces for anemia therapy  Used to overcome anemia from cancer, cancer treatments, or dialysis, avoid blood transfusions  Amgens first blockbuster products with 2.5 billion dollars in sales in 2010   Safety issues-overuse leads to strokes and heart attacks. Thickening of blood  Abuse in endurance sports (cycling)  ▯ Removal of co2 in tussues ▯ Action of carbonic anhydrase maintains co2 concentration gradient from cells(high) to plasma(low). Some co2 complexes with deoxygenated hemeglobin ▯ ▯ ▯ In active muscles- hemoglobin readily unloads oxygen ▯ ▯ ▯ Purpose of excretory system  Blood carries nutrients and waste requires filtration to remove garbage  Maintains osmotic balance of cells to prevent extreme volume changes  Requirements and mechanisms vary depending on organisms environment o Live in fresh water- need to excrete water, conserve solutes o Live in ocean- equilibrate extracellular fluids ▯ ▯ Waste products of metabolism- nitrogenous waste must be excreted and or detoxified. Co2 and water are also wasted but those are easily taken care of.  Ammonia  Ureotelic  Uric acid (relatively insoluble)  Urea (relatively soluble) ▯ ▯ Functions  Filter body fluids  Actively secrete and reabsorb specific molecules  Structures o Invertibrates0 have diverse excretory systems o Vertebrates have kidneys ▯ KIDNEY  The nephron is the functional unit of the kidney 3 major parts of nephron 1. renal corpuscule=glomerulus and Bowmans capsule where filtration occurs o 2 arterials in between. Not “regular” 2. renal tubule is the site of secretion and absorption, surrounded by capillaries 3. collecting duct=site of urine processing, where concentration or dillusion ▯ the concentrating ability of the mammalian kidney depends on its anatomy  entry/exit of blood on concave side  nephrons 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  ▯ renal corpuscule structure/function ▯ glomeruli are highly permeable capillary beds ▯ bowmans capsule cells surround the glomerlu ▯ podocytes are surface cells of the bowmans capsule ▯ ▯ blood pressure forces water and small molecules from glomerulus into bowmans capsile  small molecules=waste products such as glucose amino acid, salts, waste  proteins are too large to get out of the blood which is a wonderful thing ▯ cells and large molecules are retained in blood ▯ ▯ under pressure getting forced out into bowmans capsule  pressure from the beating of our heart  regulated by arterioles leading into and out of these capillary beds  ▯ blood enters a nepharons vascular component by the way of the afferent arteriole ▯ ▯ through the glomerulus (in the larger scheme of things) but it starts at the afferent. Afferent-glomerulus( which is part of the vascular component) ▯ ▯ ▯ Renal tubule structure/function ▯ ▯ Nephron tubules may loop across the kidney ▯ 4 specialized zones  proximal convoluted tubule  loop of Henle  distal convoluted tubule  collecting duct- receives material from nephrone  ▯ Cells structure in the different zones of the renal tubules reflects functions ▯ Proximal convoluted tubule- transports nacl out of the tubular fluids and water follows, also transports glucose. Things that the body tries to save are pulled out in the proximal tubule and sent back into the blood supply. NOT waste products  Macrovili  Mitochondria REQUIRES ENERGY TO TRANSPORT ▯ ▯ Loop of henle (thin portion)  Permable to water and small molecules  ▯ Distal- transport of nacl out of ▯ Collecting duct little active tansport- urine concentration through osmosis ▯ ▯ Proximal convoluded tubule ▯ Functions- major site of reabsorption of salt glucose and aa’s. water follows by osmosis. No active transport of water ▯ Ph regulation by secretion of protons, reabsorption of bicarbonate. BICARBONATE Buffer system ▯ Materials removed from tubules returned to venous blood via uptake in peritbular capillaries ▯ Blood pH affected by  Diet  Exercise  Disease states ▯ Kidneys excrete acids and conserve bases ▯ ▯ Lungs and kidneys have opposite effect on the pH ▯ Lungs increase in co2. Decrease in blood pH ▯ Kidneys increase bicarbonate- increase in blood pH ▯ ALLOWS FOR THE STABILIZATION OF THE BLOOD pH ▯ ▯ Structure- cells have lots of macrovilli on lumen face. Large surface area for reabsorption ▯ ▯ ▯ LOPPS OF HENLE is the counter current multiplier ▯ Function- creates concentration gradient tin medulla by countercurrent exchange (antiparallel flow of materials used to create steep gradient)  300- 1200 mm another example of countercurrent exchange anti parallel flow of materials (oxygen in blood cs water) creates steeper gradient than parallel flow because concentration gradients maintained through area of exchange ▯ ▯ driving force of water movement= similar to osmosis ▯ tendency of solution to take up water from pure water, across a membrane  psy s- solution  psy p= pressure  dissolved solutions psy s is less than zero  psy p may be negative or positive pure water has a water potential of zero water potential=psy s + psy p dilution by pure water makes it less concentrated and makes psy s less negative. Also alters pressure potential used units of megapascals which equals about 10 atm water movement depends on evaporation, cohesion and tension of water  zylem connected water in soil (psi near zero) and air surrounding leaves (psy much less than zero)   enormous water potential gradient  starts evaporating out of the leave- mesophyll  cohesion of water via hydrogen bonding maintains continuous column of water through plant: transpiration stream  water moves under tension o can be measured o how much pressure is required o pressure bomb  unidirectional ▯ ▯ when humidity is high, root pressure results in guttation  psy s greater than psy oil solute in xylem  only enough to go up a couple centimeters ▯ if xylem sap under tension (up to 025 atm why don’t cells collapse?  Because of the rigidity of the secondary cell walls ▯ Why dont water columns break and airlock system?  Bubbles are trapped in elements where formed  Flow is maintained by network of vessels connected by pits ▯ Rate of fluid movement through xylem is controlled by  Temperature and evaporation rate  Vessel width 25-200 micrometers  Up to 45 mph  Diameter of pit membrane microchannels can be altered by salt content of sap )regulated by plants)  POTASSIUM affects the xylem flow rate. Shown through experiment ▯ Iclicker ▯ Which of the following causes tension in xylem fluid? ▯ A. transpiration at the leaf surface ▯ B. cohesive nature of water ▯ C. the narrowness of the xylem tube ▯ D. all of the above ▯ ▯ ▯ path of water and mineral entry into the root  root hairs increase surface area for absorption o specialized epidermis cells o similar to microvilli  movement though cortex may be symplastic or apoplastic  entry to stele requires symplastic movement across epidermis  following passage of endodermis, much of fluid returns to apoplast in pericycle or xylem parenchyma  ▯ ▯ casparian strips force symplastic movements across the endodermis  waxy gasket preventing apoplastic movement  creates opportunity for selective uptake of minerals (often against gradient)  uptake requires energy ▯ ▯ energy for ion uptake provided by ATP hydrolysis  no sodium potassium pump  only proton pump  protons pumped into extracellular space. Lower pH (about 5)  ph gradient and charge gradient created  charge gradient o counterbalanced by taking up cations such as potassium inside o symport couples uptake of anions and H+ driven by pH gradient ▯ hat happens to water after the entry into stele?  90% flows thorough and out of plant  rest moves osmotically into vacuoles of growing cells  cells adjust vacuolar to drive osmotic water uptake  growing areas have high water flux across vacuolar membranes  AQUAPORINS  ▯ Stomata= on/off switch for transpiration stream  Hole surrounded by guard cells  Opening and closing depends on guard cell structure and osmotically driven turgor changes  300-400 mM potassium flux between guard and surrounding epidermal cells, accompanied by anion and water flux  ion and water flux via channels and apolast: low density of pladesmata prevents “short circuiting” and ion flux and turgor change ▯ stomatal aperture controls balance between access to co2 for photosynthesis and water loss via transpiration ▯ aperture regulated by  light or low co2 promote opening  high co2 or water stress (signaled by ABA) promote closure  feedback mechanism(protecting)  signaling involved many of the intermediates described in other systems. Secondary messengers such as calcium etc etc ▯ NOT simple reversals of same process although they are moving in opposite directions ▯ ▯ What happens if a plant cant regulate its stomata?  ABA deficient mutants cannot close their stomoata  Short and wilty, partly becasue they cannot retain water needed for turgor ▯ ▯ Do plants have action potentials?  Charge difference between inside and outside of cell due to asymmetric distribution of ions  Uptake of potassium reduced negative charge inside cell:depol  ▯ Minerals plants need  Macronutrients at least one gram needed per kg of dry weight o Nitrogen, phosphorous, potassium, sulfur, calcium, magnesium  Micronutrients -less than 100 kg o Iron, chloride, manganese, zinc, copper, nickel, molybdenum  Roles may be structural, catalytic, signaling, ion balance… soil fertility partly reflects availability of mineral nutrients ▯ ▯ VASCULAR tissues in roots and shoots ▯ Phloem ▯ ▯ Carbyhydrate movement  Site and direction of movement  Driving force for movement= pressure flow  Pulse label new photosynthate by co2 feeding of lead for 1 hour  Track where photosynthate is goingby an autoradiograph ▯ Dual osmometer model  Water enters both funnels by osmosis  Phoelem loading/unloading maintains source/sink identities  Sucrose loaded at source cells  Water follows by osmosis  Sucrose unloaded at sink cells  Used to identify organs change as mature with GFP ▯ Phloem contains tow major cell types  Sieve tube elements- conducting cells, alive but have minimal organelles  Companion cells: control activity of adjacent sieve tube members, small, metabolically active, may have wall invaginations  Increase in PM surface area increase in transport  Phoelem loading involves both symplastic(from plasmodesmata) and apoplastic transfer from mesopyl cells Many plants have relatively few connections between Phoelem companion or sieve tube cells and adjacent cells in source tissues: forces apoplastic transport Sources leading by surcrose proton symport  Uses potential energy of proton gradient, created by protons pump, to drive sucrose uptake  ▯ Sap also contains amino acids and hormones, aside from sucrose ▯ ▯ Sweet transporters take sucrose to the plasmodesmata? Water osmosis follows ▯ ▯ Photosynthesis ▯ Lightchemical energy ▯ Supports all life on earth ▯ Produces sugar and o2algae responsible for 50-60% ▯ ▯ Experiment involving heavy oxygen used to show what the source of o2 produced was by photosynthesis . water is the source of o2 ▯ Requirements ▯ 1. light ▯ 2. pigment for absorption ▯ 3. co2 access ▯ primary location for where these requirements are met: the leaves ▯ ▯ ▯ thylakoid- sites of light reaction. Stacks ▯ stroma- site of dark reaction ▯ ▯ ▯ 3 processes ▯ in thylakoid ▯ 1. light capture ▯ 2. pigment ▯ regeneration ▯ ▯ in stroma ▯ 3. dark reactions=light independent ▯ ▯ chloroplast pigments absorb red and blue light ▯ wavelengths not absorbed give the pigment its color. Reflect green light, absorbing red ▯ ▯ chlorophyll: major photosynthetic pigment ▯ magnesium in center ▯ alternating single and double bonds-delocalized ▯ ▯ beta carotene, carotenoids bind ▯ lght harvesting complex proteins bind chlorophyll and carotenoids ▯ ▯ Review  Light reactions occur in thylakoid sacks  Light energy absorbed by pigments  Absorption spectra reflect chemical structure of pigments  Pigments associated with proteins in thylakoid membranes Oxidization of chlorophyll. Needs to be regenerated to go through the reaction again Antenna system  Contains about 200 chlorophyll a and b  50 carotenoids  multiple aproteins present in trimmers  1 reaction center chl a adjacent to the primary electron acceptor____ ▯ ▯ how light energy converted to metabolic energy  chemiosmostic ATP synthesis  electron energy is increased by light capture  energy released during electron transfer drives proton movement into thylakoid and created pH gradient  gradient drives ATP synthesis ▯ PS I and PS II photosystems  Differ in arrangement of pigments and first electron acceptor  Electros enter different transport chains- different functions o Different absorption peaks o I- 700 nm o II- 680 nm- HIGHER ENERGY ▯ PS I is the most primitive form  P700 at reaction center  In absence of PS II, electron transfer is cyclic  Energy increased, goes into redox chain and produces ATP synthesis, goes back into p700 to get another electron  No oxygen or NADPH  Only produces 1 ATP/2 electrons ▯ Also have z- scheme (non cyclic) which required for PSI and PSII function , ultimately producing NADP+ after going through the electron transport chain. PS IIETCPS INADP+ reductase  Both ATP and NADPH produced  Water split into radicals  Water splitting causes the protons to be driven into the thylakoid interior.. so the thylakoid interior is about 1000X higher in proton concentration compared to the stroma. Pretty acidic interior. Stroma is about pH 8. Big concentration gradient. Water splitting amplifies this gradient  ATP synthase converts proton gradient energy into energy to make ATP  ▯ Mitocondria vs chloroplast  Both create a proton gradient across membrane. Small enclosed membrane space has higher proton concentration  Both cases: pH gradient drives synthesis  Different electron carries and reducing agents involved (NADPH vs NADH) ▯ ▯ Advantage of scheme over cyclic photos ▯ ▯ ▯ ▯ Dark reactions of photosynthesis  All plants do c3 fixation, some plants do c4 fixation  C3=calvin cycle ▯ CALVIN ▯ 1. carboxylation ▯ 2. reduction and sugar production  atp and nadph are needed ▯ 3. regenerate RuBP (sugar shuffle)  atp consumed ▯ total cycle consumes 3 ATP and 2 NADPH per co2 fixed ▯ takes SIX turns of the cycle to make an entire sugar (since 6 carbons in a sugar and each cycle creates 1 carbon) ▯ ▯ experiments done to figure this out ▯ strategy used to decipher pathway  thin flask of green algae taken under bright light source  feed algae co2  kill cells at different time points  separate and identify metabolites by chromatography and autoradiography  done in two solvents- 2 dimensional separation  labeling for short (2-3 seconds), earliest product is only labeled  minutes- everything labeled ▯ 3PG accumulates in dark ▯  surprising to find the precursor to a 3 C compound be a 5 C compound catalyzed by Rubisco RuBP carboxylase  20-40% total plant proteins. Most abundant ▯ do all plants use c3 pathway or is this a fluke of algal biochemistry?  Tropical plants shows initial labeling in c4 compounds fixation ▯ When/why is c3 pathway inadequate?  Rubisco can act as an oxygenase or carboxylase o Co2 coupling produces productive cycle o O2 coupling actually inhibits growth (photorespiration) o Determined by affinity of rubisco  Or relative levels of dissolved co2 and o2  Photorespiration occurs at high temp. o Water splitting radical reaction produces o2 o Stomata start to close which decreases gas exchange, increases dissolved o2/cos2 ratio o O2 competes with co2 to bind to robusco ▯ Light dependent ▯ Consumes oxygen ▯ Releases co2 ▯ C4 uses a different initial incorporation step  PEP carboxylase does not bind to o2 which means no competition  Goes from a 3 carbon compound to a 4 carbon compound  C4 leafs (bundle sheath) are surrounded by mesophyll cells. No gaps  Kranz anatomy: bundle sheath cells ringed by mesophyll surrounding BS. Isolates from gases  Calvin cycle occurs inc ells with high co2/o2 ratio IN THE BS cells 


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