Marking Period 2 Grades Finish grading ecology projects Chapter 6 Quiz AP Lab 4 PreLab Quiz Microscope Lab Cells Quiz/Test on Monday One of your case studies

Solutions and Water Potential PSI Solutions and Water Potential Chapter 7 Agenda: Ch 6 Quiz Notes - Practice Hw: Pre-Lab

Interactive Question 7.5 Side A Side B 1 M Glucose 0.2 M Fructose 5/2/2018 Interactive Question 7.5 A solution of 1 M glucose is separated by a selectively permeable membrane from a solution of 0.2 M fructose and 0.7 M sucrose. The membrane is not permeable to sugars. Indicate which side initially has more free water molecules and which side has fewer. Explain the direction of osmosis. Side A Side B Clustering of free water molecules around solute particles lowers the proportion of free water that is available to cross the membrane. 1 M Glucose 0.2 M Fructose 0.7 M Sucrose

Interactive Question 7.6 A. What osmotic problems does the freshwater protist Paramecium face, and what adaptations enable it to osmoregulate? B. Compare the ideal osmotic environment for animal cells and plant cells.

Cell survival depends on balancing water uptake & loss = OSMOREGULATION http://www.microscopy-uk.org.uk/mag/imgjun99/vidjun1.gif Paramecium vs. pond water Paramecium is hypertonic H2O continually enters cell to solve problem, specialized organelle, contractile vacuole

TONICITY- ability of a solution to cause a cell to lose or gain water Refers to the concentration of SOLUTES Is a RELATIVE term, comparing two different solutions Solute-substance that is dissolved Solvent- substance solute in dissolved in Solution = solute + solvent

Animation See an animation Osmosis1 http://faculty.etsu.edu/currie/images/osmosis1.jpg

Osmosis… .05 M .03 M Cell (compared to beaker)  hypertonic or hypotonic Beaker (compared to cell)  hypertonic or hypotonic Which way does the water flow?  in or out of cell

5/2/2018 Hypo Iso Hyper Hyper: Animal cell will crenate, Plasmolysis: Plant cell Hypotonic: Animal cell with swell Cytolysis Turgor pressure provides support for nonwoody plants. Plant cells = iso = flaccid. Need hypotonic.

Animal

I’m a slug baby. Ain’t no shell over here. Water rush out of the cell to surface. Decrease Water Potential

Water moves from High Free Energy (Potential) to Low Potential Water potential (ψ): H2O moves from high ψ  low ψ potential Water potential equation: ψ = ψs + ψp Water potential (ψ) = free energy of water Solute potential (ψS) = solute concentration (also called osmotic potential) Pressure potential (ψP) = physical pressure on solution; turgor pressure (plants) Pure water: ψP = 0 MPa Plant cells: ψP = 1 Mpa

Bars or Megapascals Water potential is measured in bars or megapascals (MPa) 1 MPa = 10 bars Water potential is the tendency of water to leave one place in favor of another. The water pressure of pure water in an open container is zero ψ = 0

Slug Example Pure Water = 0 Bars Outside of cell High concentration or potential to LOW Inside of cell

Where will WATER move? From an area of: higher ψ  lower ψ (more negative ψ) high pressure  low pressure Solution concentration low -->> high

Diffusion Water Trees Pure water = 0

ψ = ψs + ψp Two plant cells Solute Potential Osmotic Pressure Adding solutes is going to LOWER the solute potential. Less room for water.

ψ = ψs + ψp Two plant cells Solute Potential Osmotic Pressure = -5 bars = 2 bars Adding solutes is going to move water into the other cell. Osmotic pressure will increase. Turgid.

Calculating Solute Potential (ψS) 5/2/2018 ψ = ψs + ψp Calculating Solute Potential (ψS) ψS = -iCRT i = ionization constant (# particles made in water) NaCL = 2 Sucrose = 1 C = molar concentration (moles/liter or M) R = pressure constant (0.0831 liter bars/mole-K) T = temperature in K (273 + 0C) The addition of solute to water lowers the solute potential (more negative) and therefore decreases the water potential. NaCl is 2 because if you add 1 mole of NaCl it breaks apart into 1 mole of Na and 1 mole of Cl.. Increasing i is going to lower the solute potential (s), Increase concentration also lower solute potential (s) Increase temperature lower water potential

Which chamber has a lower water potential? Which chamber has a lower solute potential? In which direction will osmosis occur?

Sample Problem Mr. Anderson

Sample Problem Calculate the solute potential of a 0.1M NaCl solution at 25°C. If the concentration of NaCl inside the plant cell is 0.15M, which way will the water diffuse if the cell is placed in the 0.1M NaCl solution?