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Diffusion Osmosis Lab * Review the Day Before *

Diffusion Osmosis Lab * Review the Day Before *. Water Balance- Review before Lab (pg. 117-118). Osmoregulation~ control of water balance Hypertonic~ higher concentration of solutes Hypotonic~ lower concentration of solutes Isotonic~ equal concentrations of solutes Cells with Walls :

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Diffusion Osmosis Lab * Review the Day Before *

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  1. Diffusion Osmosis Lab*Review the Day Before*

  2. Water Balance- Review before Lab(pg. 117-118) • Osmoregulation~ control of water balance • Hypertonic~ higher concentration of solutes • Hypotonic~ lower concentration of solutes • Isotonic~ equal concentrations of solutes • Cells with Walls: • Turgid (very firm) • Flaccid (limp) • Plasmolysis~ plasma membrane pulls away from cell wall

  3. Help with Data Collection & Analysis • Mass Difference: Final – initial (absolute diff.) • % Change in Mass: Final – initial x 100 initial **Why do we use the % change in mass instead of simply the straight difference? • Plot your data on the graph. • Determine the molar solute concentration of the potato cores. How??? *Hint: Where does your line cross “0”

  4. Calculating Solute Potential • Variables involved: i, C, R, T i = ionization constant: NaCl = 2.0 (Na+ & Cl-) **for sucrose it will be 1.0 (it doesn’t ionize) C = Molar concentration of your potato (determine from your graph) R= rate constant: 0.0821 L · atm (bar) mol · K T = Temperature: K

  5. Calculating the Solute Potential (s) • s = - iCRT • Sample Calc. A 1.0 M sugar solution @ 22° C under standard atmospheric conditions: s = -(1)(1.0mol)(0.0821 L · bar )(295K) L mol · K s = -24.22 bars

  6. Dialysis Tubing Experiment

  7. An Artificial CellPermeable to: monosaccharides & waterImpermeable to: Disaccharides

  8. Potato Cores • Review Molarity and how to make solutions before your group begins

  9. What to have Ready for Lab- Day 1 • Bring in a Large Potato if I tell you to (one per lab table) • Have the Pre-lab finished w/quiz • Write a statement of purpose or reason for doing this lab in your journal. Take notes in journal. • Materials list - review the handout • Hypothesis: • Data Table/ Graphs – review the lab handout the day before so you’ll know what you’re collecting & analyzing before you begin!

  10. Key Sections for Formal Lab • Title • Intro/Background: Defining water potential Importance & Sig. Of the lab • Hypothesis & reason for your prediction • ID Experimental Variables • Materials (diagram & visual of set up optional) • Procedure • Data: tables charts & graphs • Analysis- be thorough • Conclusion & Evaluation: error & improvements

  11. Pre- Lab Questions • Suppose you have an artificial cell that was permeable to monosaccharides and impermeable to disaccharides. What would happen to the cell if it had 0.80 M maltose and 0.85 M fructose in it and was placed in a solution containing 0.45 M glucose, 0.65 M fructose, and 0.40 M sucrose. a) Which direction would the water flow? b) Which area has a higher water potential? c) What would happen to the concentration of the maltose inside the cell (increase, decrease, remain the same)? • What is the ionization constant (i) for sucrose?

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