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Lecture

Lectures 15-19

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Department
Biology
Course
BIOL 120
Professor
Simon Chuong
Semester
Winter

Description
LEC 15Plant Transportsymplastic transportMolecules move thru living space interior of cells bounded by plasma mem o Diffusionmove across mem o Facilitated transuse transport protein o Active transtransport proteinATP gradient o Endoexo cytosisenterexit by making vesicle o Osmosisconc gradientapoplastic Transportmolecules move thru space around protoplast external to plasma memneed semi permeable barrier for movement across membranes Water Movement Principleswaterliving cell solventmovement by 3 processes o Bulk FlowWater molecules move in mass in response to potential energy differences o DiffusionSpontaneous movement of water down a conc Gradient higher to lower o OsmosisMovement of watersolvent across selectively permeable membraneLower solute conc to higher higher water conc to lowerTurgor Pressure Contributes to Cell StiffnessCell was counters turgor pressureFor plant cells to grow water must increasecell walls must expandWhy is Turgor Pressure Important to Maintaindriving force for cell expansionprovides support for cells and tissuesdrives opening of stomataphloem transporttells plant about soil water statusWater Potential Refers to measurement predicting which way water will flow bw plant cell and surroundings or between different parts of a plant ex rootsleavesDefined as combination of osmotic potential and the pressure potential the effect of cell wall pressureMeasured in units represented by Greek letter psi Water PotentialPressure potential alwayscell wall cant exert negative pressureOsmotic potential always zero or Most living plant cells have water potential of negative or zeroIf water potential is negative cell has more capacity to take up waterHypotonic Solutionssolution surrounding cells has a lower conc of solutesWater flows into cell but cell wall prevents ruptureIsotonic Solutionssolution surrounding cells has same conc of solutesWater at equilibrium but cell not turgid Hypertonic SolutionsThe solution surrounding cells has a higher conc of solutesWater flows out of cells and plasma mem shrinks away from wall plasmolysisSymplastic connections can be compromised and cause cell deathTransport in PlantsBidirectional process o From roots to shootfrom leaves to the rest of the plant o Mediated by vascular system made up of two complex tissues xylem and phloemOverview of WaterSolute Transport
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