Lab+1+Diffusion+and+Osmosis

Your first REAL lab!

=**//__ AP Lab 1 Diffusion and Osmosis __//**= =** Objectives ** At the completion of this laboratory you should be able to: = __ Materials __ · Solution of soluble starch and 15% glucose · Solution of Iodine · Glucose test tapes · Dialysis tubing, string · beakers, graduated cylinders, pipettes · Distilled water __ Procedure __
 * Describe the mechanisms of diffusion and osmosis.
 * Describe how solute size and molar concentration affect the process of diffusion through a selectively permeable membrane.
 * Describe the effects of a selectively permeable membrane on diffusion and osmosis between two solutions separated by a membrane.
 * Relate osmotic potential to solute concentration and water potential.
 * Measure the water potential of a solution in a controlled experiment.
 * Describe the effects of water gain or loss in animal and plant cells.
 * Experimentally determine the water potential of an unknown solution.
 * Calculate the water potential of living plant cells from experimental data
 * Part A Diffusion **
 * 1) Pour 15 ml of the prepared glucose/starch solution into graduated cylinder.
 * 2) Tie a knot into one end of the soaked dialysis tubing.
 * 3) Open the tubing and pour in the glucose starch solution.
 * 4) Determine if glucose is present by using an indicator strip.
 * 5) Tie a knot into the open end of the tubing.
 * 6) Fill a beaker with distilled water. Add potassium iodide (IKI) to the beaker.
 * 7) Determine if glucose is present by using an indicator strip.
 * 8) Wait 30 minutes.
 * 9) Remove dialysis bag and observe.
 * 10) Determine the glucose content in the beaker using an indicator strip.
 * 11) Determine the glucose content in the dialysis bag.

Part B Osmosis

__ Procedure __ This experiment will be done as a dry lab to save time. You did a similar lab in Honors Biology you can reference. 1. Obtain a strip of presoaked dialysis tubing. 2. Tie off one end of the dialysis tubing to form a bag. Pour 10 ml of solution into the bag. The solutions will be: a) 0.0 M sucrose (distilled water) b) 0.2 M sucrose c) 0.4 M sucrose d) 0.6 M sucrose e) 0.8 M sucrose f) 1.0 M sucrose 3 . Remove most of the air from each bag. Tie off the other end of the bag leaving sufficient space for the expansion of the contents in the bag. 4. Carefully blot the bag dry and record its initial mass (grams) in Table 1. 5. Immerse the bag into a beaker containing approximately 100 ml of distilled H 2 O. The bag must be __totally__ immersed in the water. Add more water to the beaker if necessary to immerse the bag. 6. Let stand for approximately 30 minutes. 7. At the end of 30 minutes, remove the bag from the beaker. Carefully blot dry and re-mass the bag. Record the final mass of the bag in Table 1. 8. Calculate the percent change of the bag from initial mass to final mass using the formula below and record the result in Table 1.

% Change = __Final mass - Initial mass__ X 100 Initial mass

Table 1. Dialysis Bag Data.


 * Treatment || Initial Mass (g) || Final Mass (g) ||  % Change ||
 * 0.0 M sucrose || 25.8 || 26.0 || ||
 * 0.2 M sucrose || 26.3 || 26.8 || ||
 * 0.4 M sucrose || 26.0 || 28.1 || ||
 * 0.6 M sucrose || 26.1 || 29.0 || ||
 * 0.8 M sucrose || 26.2 || 30.1 || ||
 * 1.0 M sucrose || 26.3 || 31.1 || ||

Unknowns A = 15 % change B = 25 % change


 * Part C Determining the Water Potential of Apple Cells**

__ Procedure __ Continue to work in the same groups. Each group should prepare the following: 1. Pour 100 ml of your assigned liquid into a labeled beaker. 2. Get a couple slices of apples from the cart. 3. Determine and record the initial mass (grams) of the combined apple slices. 4. Place the apples in your beaker and let stand overnight. 5. Visit the lab the next day at approximately 24 hours after your lab. Remove the slices from the beaker. Blot dry and weigh. Record the final combined mass on the sheet left out by the instructor. //Note// - the % mass change may be positive or negative. Be sure to give the correct sign with your group's result.
 * 2010 Lab 1 Data ||  ||   ||
 * Table 2 Apple Data ||  ||   ||
 * Molarity |||| Mass Before || Mass After ||
 * Water || 5.61 ||  || 5.88 ||
 * || 8.32 ||  || 8.33 ||
 * 0.2 || 4.34 ||  || 4.71 ||
 * || 9.19 ||  || 9.84 ||
 * 0.4 || 4.22 ||  || 4.7 ||
 * || 3.8 ||  || 4.32 ||
 * || 5.66 ||  || 6.62 ||
 * 0.6 || 7.26 ||  || 7.28 ||
 * || 7.53 ||  || 10.65 ||
 * 0.8 || 10.7 ||  || 10.16 ||
 * || 10.3 ||  || 7.12 ||
 * 1 || 3.34 ||  || 2.54 ||
 * 0.8 || 10.7 ||  || 10.16 ||
 * || 10.3 ||  || 7.12 ||
 * 1 || 3.34 ||  || 2.54 ||


 * Part D Onion Cell Plasmolysis

Link to website: **[|**http://www.dnatube.com/video/2775/Onion-Cells-Plasmolysis**]


 * Pictures**

Figure A: Red Onion (x400) in distilled water []



Figure B: Red Onion (x400) in salt water []