İstanbul Bilgi Üniversitesi BIOE 222 CELL BIOLOGY LABORATORY Experiment 2 2023-2024 SPRING Dr. Tuğba KÖSE Ar. Gör. Betül BUDAK Page 1 EXPERIMENT 2: OSMOSIS and Diffusion Part 1. Diffusion with Starch solution Background: Diffusion is the passive movement of particles of a solute from an area of high concentration to an area of low concentration. Osmosis is the passive movement of a solvent, such as water, through a semipermeable membrane from a region of high solvent concentration to an area of low solvent concentration. Diffusion Solute molecules move from high to low concentration (VS) Osmosis Solvent molecules move from low to high solute concentration Solute molecules Solvent molecules High solute concentration Diffused evenly (Equilibrium) Semipermeable membrane Low solute concentration High solute concentration Same concentration (Equilibrium) Science Facts.net Solute: a substance that has been dissolved in a given solution. Solvent: a substance, usually a liquid, that is capable of dissolving or dispersing one or more other substances. Exp: To create salt-water, salt is dissolved into water. Solute: salt Solvent: water Semipermeable membrane: A membrane or barrier that allows only certain molecules or substances to pass through it and does not allow others. Ex: Dialysis tubing acts as a semipermeable membrane. Lugol's iodine: a solution of potassium iodide that turns blue in the presence of starch. Page | | 2 Laboratory Exercise: Materials: • 10 cm piece of dialysis tubing • 250 mL beaker • Dental floss • Lugol's iodine . 1% starch solution Procedure: 1. Soak a piece of dialysis tubing in 250 mL of deionized water for at least 5 minutes. 2. Seal off one end of the dialysis tubing by gently twisting the end and tying dental floss tightly around it. 3. Gentle rub your fingers on the other end of the tube to open it. Make sure to open it as far down as you can towards your knot. 4. Pipette a small volume of 1% starch solution into the dialysis tube. Make sure you leave enough room to tie the end closed. 5. Twist the open end of the dialysis tubing closed and tie off with another piece of dental floss. 6. Trim excess dental floss and dialysis tubing from the ends of your sealed dialysis bag. 7. Add a few drops of Lugol's iodine to your beaker of 250 mL of water until it appears a pale yellow. 8. Place your dialysis bag into the beaker and wait 30-40 minutes. Review the background information and fill in the Start of Experiment section of Table 1. 9. After 30 min have elapsed, fill out the remainder of Table 1 and answer questions 1-4. Results: Table 1: Dialysis Tubing Contents Beaker Contents Start of Experiment Color Contents End of Experiment Color Contents Page 3 Questions: 1. What happens when starch interacts with Lugol's iodine? 2. Based on your results, was the starch able to pass through the semipermeable membrane that was the dialysis tubing? Explain how you reached your conclusion. 3. Based on your results, was the Lugol's iodine able to pass through the semipermeable membrane? Explain how you reached your conclusion. 4. What would happen if the contents of the dialysis bag and beaker were reversed? What would the final colors of the dialysis tubing content and beaker content be? (The beaker would be filled with 1% starch solution and the dialysis tubing would contain water and Lugol's iodine.) Part 2. Osmosis in Elodea Leaf Cells ● Take 3 microscope slides, draw a perpendicular line dividing each slide into two parts and label the all parts according to the sample and the solution to be added. • • • • Take an Elodea leaf, cut it into two. Using a micropipette, place 80 μl of water to one side of the slide, and place the half Elodea leaf on the solution. Place the coverslide on the leaf. In the same slide, place 80 µl of 0.5 % NaCl solution to the other side of the slide, and place the half Elodea leaf on the solution. Place the coverslide on the leaf. Observe and compare them under 40X magnification 5 min after the solutions are added. Repeat the procedure and compare water with 5% NaCl. For the third slide, compare the effects of 0.5 % NaCl solution and 5 % NaCl solution on Elodea leaf cells. Note which solution induces shrinking or swelling. You should define the solutions in terms of hyper-, hypo- and isotonicity. Page | 4/n • Cover Page How to write? • Name of Experiment • Aim of Experiment • Introduction Materials and Methods • Results • Discussion 1 Table of Content Introduction......... • Materials & Method......... ● Results.......... 1 .3 ........7 2 TABLE OF FIGURES ? 3 TABLE OF FIGURES Figure 5.1: The name of the figure DO NOT PUT «FIGURES» ON THIS PAGE! 4 St TABLE OF FIGURES Figure 1.1: The name of the figure….... ● Figure 1.2: ……………………. ● Figure 3.1: !Each figure has to have a name!!! Figure 1.1: The name of the figure…………………………………..1 Number of Chapter Number of Figure for that Chapter .1 18 5