BIOL 240W 1st Edition Lecture 7 Outline of Last Lecture Review of Chapters 37 and 35 for first exam cycleOutline of Current Lecture I. Plant EvolutionII. Three Transport Routes for Water and SoluteIII. Solute TransportIV. Short-Distance Water TransportV. Solutions and OsmosisCurrent LectureI. Plant Evolutiona. Evolution of vascular tissue in land plants allowed water, mineral, and products ofphotosynthesis to be transported long distances.b. Adaptations are a compromise between enhancing photosynthesis and minimizing water loss. For example, leaves that are photosynthesizing need water that is moved up from roots, but the stomata must also be open to acquireCO2. This leads to water loss when the stomata are open.c. Apoplast- everything outside of the plasma membrane. i. Includes cell walls, extracellular spacesii. Xylem is part of the apoplast (vessel elements and tracheids)d. Symplast- consists of the cytosol. Is the living part of the plant. Includes plasmodesmata which is important for connection between individual cells.II. Three Transport Routes for water and solutea. Cells align back-to-back allowing a route minerals, water and solute can take. b. Apoplastic route- continuum through cell walls and extracellular spacesc. Symplastic route- continuum through cytosol, crossing one plasma membrane entering the plantd. Transmembrane route exists across multiple cell walls and membranesIII. Solute Transporti. Plasma membrane is selectively permeable; it controls short-distance movement of solute into and out of cellsii. Ions create a membrane potential due to differential distribution of ions inside and outside of cellThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.iii. Membrane potential allows substances to move based on a gradientiv. In plants, membrane potential is established through hydrogen ion pumps(different from sodium-potassium pumps in animals)1. ATP is used to pump protons across membrane. This creates a membrane potential2. Large solutes (ex: sucrose, nitrate), which cannot enter the cell by themselves, are co-transported with protons through a protein channel.v. Ion channels allow specific ions in and out of cell. They are gated, so movement only occurs after there is a stimulus.IV. Short Distance Water Transporta. Short distance transport of water is defined as the movement from one cell to another. Not from roots to leaves.b. Water can diffuse in or out of cell in a process called osmosis. This is dependent on the solute concentration and pressure.c. Water moves from higher water concentration to lower water concentrationd. Water potentiali. Measurement combining effects of solute concentration and physical pressure. This determines the direction of movement of water.ii. Abbraviated as Ψ. The unites are megapascal (Mpa)iii. Changes in the water changes the value of Ψiv. Solute concentration + pressure = water potential (Ψ = ΨS + ΨP)v. Water potential decreases with addition of solutes because these solutes bind to water molecules, reducing their ability to move and do workvi. Water moves from higher potential to lower potentialV. Solutions and Osmosisa. Hypotonic solutions are solutions surrounding a cell that cause the cell to take upwater. These solution have less solute than inside the cell, so the cell takes up water to dilute solutes.b. Isotonic solutions outside of the cell cause no net movement of water into or outof cell.c. Hypertonic solutions surrounding the cell cause the cell to lose water. Water from the cells moves across the cell membrane in an effort to dilute the solution.d. Rigid plant cell walls are most efficient in hypotonic solutions because the rigid cell wall creates turgor pressure when water in the cell creates pressure against the cell wall.e. Plasmolysis is the shrinkage of the cytoplasm and detachment from the cell wall in a hypertonic
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