Isotonic solution - the inside of the cell will have the same concentration of ions as the solution, so there is no net movement of water into or out of the cell (think about injections). Hypotonic solution - the inside of the cell will have more solutes than the solution, so water will rush in and cause it to swell and/or lyse. Hypertonic solution - there is more water present in the interior of the cell than in the external solution so water leaves the cell and it becomes crenated Final Note: Remember that these terms are relative - a solution with a 10% solute concentration will be hypertonic to one with a 5% solute concentration. However, the 10% solution is hypotonic to a solution with a 15% solute concentration. A FEW HINTS ABOUT THE FOLLOWING EXPERIMENTS: 1. Set up experiment 1 first and get it going - it takes the longest. 2. Divide labor among the members of your lab group - at least 2 people should be working on experiment 1. 3. Experiment 2 can be set up and done last - it only takes about 15-30 minutes. 4. Be sure to read through ALL the instructions before beginning any of the experiments! 2
Lab 3 Nur 0002 Experiment 1: Concentration Gradients and Rates of Osmosis In this experiment you will examine the effect of a concentration gradient on the speed of water movement across a semipermeable membrane (dialysis tubing). You will compare the rate of osmosis for 3 different known combinations of solutions and 1 unknown. Bag Setup BAG INSIDE BAG IN BEAKER 1 1% sucrose tap water 2 5% sucrose tap water 3 10% sucrose tap water 4 unknown C unknown D MATERIALS: Triple beam balance Dialysis bags soaking in water 4 beakers, 1 funnel Solutions: 1% sucrose, 5% sucrose, 10% sucrose, unknowns Paper towels; watch NOTE : Follow the procedure for each dialysis bag until completion before starting another one - this experiment requires a sequence of timed measurements - don’t try to prepare all the dialysis bags simultaneously! 1. Take one dialysis bag out of the beaker and tie off one end (instructor will demonstrate how to tie off the bags to prevent leaks). Fill the bag with 10-15 mls (actual amount is not that important) of 1% sucrose using the funnel. Squeeze any air out of the bag, being careful NOT to use your fingertips (the oil on the skin of your fingertips can damage the dialysis membrane). Tie off the opposite end of the bag. 2. Dry the bag thoroughly on paper towels, especially the knotted ends. Weigh the bag on the balance (1 decimal place is sufficient). 3. Put the bag in a labeled beaker and fill with enough tap water to just cover the bag - NOTE THE TIME. 4. Fill the second dialysis bag with10-15ml 5% sucrose, tie it off, dry it, weigh it, put it in a separate, labeled beaker with enough tap water to cover the bag, and again NOTE THE TIME.
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