Transcript H +
Transport in Plants I If you're not part of the solution, you're part of the precipitate. - Steven Wright Business • Quiz: mean = last term, ~6/9 (not good enough), ? – didn’t study enough, – studied, did well, with tinkering will master, – studied, but didn’t do too well, • probably memorized terms, without grounding the words in reality. • Midterm I: one week from Friday, – Essay questions due Tuesday afternoon, 3 pm. • email to [email protected], – Subject Line must say 206 Question, – Include your name, if your email address is esoteric, • 2 extra credit point (maximum) if you provide at least one GOOD question, and email it, on time, and with correct subject line. Rote Not so Good Concept/Process oriented Question Good Integrated question, i.e spanning chapters Excellent Today • Introduction to Transport, • Mechanisms of Transport, – passive, – active, • Questions, Extra Credit? Transport …molecular and ionic movement from one location to another, – H2O, – Sugars, – Minerals, – Gases, – Other Macromolecules: proteins, RNA, hormones, etc. Plant Transport (What’s Transported) Xylem • H2O, – uptake by roots, transport via xylem, loss to the atmosphere and metabolic process, • Minerals (in solution), – Uptake by roots, loss to senescence, herbivory, etc. Plant Transport (What’s Transported) Stomates • Gases, – CO2, O2, H2O. – N2, ethylene, etc. Plant Transport (What’s Transported) Phloem bydirecional • Sugars, • other organics, – hormones, – amino acids, – etc. Plant Transport (What’s Transported) Gas Exchange/Respiration • Roots, » – uptake O2, – discharge CO2. Plant Transport Across Membrane(s) Everything First Symplastic and Apoplastic Then What Drives Transport? Gravity, Pressure, Electrical fields, (for charged substances), Concentration gradients, (entropy-driven diffusion). Mechanisms of Transport in organisms • Diffusion, by molecular motion, – good only at short distances, • Pump, Channel and Carrier mediated transport, – small molecules across membranes, • Osmosis (water across membranes), • Bulk Flow, – efficient large-scale, mass movement. Fick’s First Law “Uber Diffusion” (1855) Adolf Fick concentration gradient flux density Dcs flow rate Js = Ds Dx change in distance diffusion constant Adolf Fick: Contributions • Ophtalmotonometer – Intraocular pressure • Aneroid manometer – Vascular grad (BP) • Pneumograph – Peripheral thorax variation link • Plethysmography – I/O of blood, air in lungs, etc. • Dynamometer – Muscle output • Laws of diffusion 1855 • Contact lens Fick’s Law and Organisms (tc = 1/2) for a molecule to move (p = 0.5) a set distance (L)... tc = 1/2 = L2 Ds … is equal to the distance (L) squared divided by the diffusion coefficient (Ds). • Ds for sucrose is ~10-9 m2 s-1, – 50 mm: – 1 m: tc = 1/2 = 2.5 seconds, tc = 1/2 = 32 years. Fick’s Law and Organisms 50mm Chlamydomonas reinhardii Bryophytes Choleochaete orbicularis Trees ? Mechanisms of Transport in organisms • Diffusion, by molecular motion, – good only at short distances, • Pump, Channel and Carrier mediated transport, – small molecules across membranes, • Osmosis (water across membranes), • Bulk Flow, – efficient large-scale, mass movement. Membranes Plasma Membrane (1x), Plastids (2x), Mitochondria (2x), Vacuole (1x), Golgi, ER (1x), Peroxisomes, etc. ( 1x). Coordinated Transport Arabidopsis Genome H+ (protons) ATP synthase Transporters - carriers, - channels. ATP hydrolase (ATPase) Adapted from Biochemistry and Molecular Biology of Plants, pp. 115 ATP Pumps all organisms vacuolar organelles P-Type ATPases Phylogentic Family Tree P-Type ATPases plasma membrane …ATP driven cation pumps (typical), 10 transporters NA+ K+ H+ K+ H+ 2+ Ca Cd2+ Hg2+ Cu2+ animals plants, animals, fungus, yeast animals, plants, fungus, yeast bacteria, animals, plants, etc. + Plasma Membrane H -ATPases H+ Plasma Membrane H+ H+ H+ + H+ H+ H Proton Pump H+ symport (ATPase) ATP ADP + Pi X 2 H+ H+ antiport H+ 2 H+ X D 300 mV ions Transport channels Mechanisms of Transport • Diffusion, by molecular motion, – good only at short distances, • Channel and Carrier mediated transport – small molecules across membranes, • Osmosis (water across membranes), • Bulk Flow, – efficient large-scale, mass movement. Osmosis …the diffusion of water across a selectively permeable membrane, – water (free) moves from a region of higher H2O concentration, to a region of lower H2O concentration, until in equilibrium, …the concentration of water is lowered by the addition of solutes. Mechanisms of Transport • Diffusion, by molecular motion, – good only at short distances, • Channel and Carrier mediated transport – small molecules across membranes, • Osmosis (water across membranes), • Bulk Flow, – efficient large-scale, mass movement. Bulk Flow Jean Louis Marie Poiseuille (Poiseuille’s Law, ~1838) …the concentrated movement of groups of molecules, – in response to gravity, i.e. rain, rivers, etc., – in biological systems, most often in response to pressure. Volume flow rate = in a cylinder pr4 DYp 8h Dx viscosity (h) viscous: tendency to resist flow pressure gradient distance Increase Flow? Increase radius. Lower Viscosity. Increase Pressure. Shorten Distance. Volume flow rate = viscosity (h) pr4 DYp 8h Dx pressure gradient distance Friday • Water and Water Potential, • Cell Water Relations, • Water Transport in Plants. Catch up in the readings, review materials from 204 and 205 if necessary.