September 23, 2014
AP Biology – 2
Lab 1: Diffusion & Osmosis
9/16/14-9/19/14; Jessica Bullock, Andrew Buchholz, Kristamae Masiclat
TITLE: Different Ways to Express Diffusion and Osmosis
Diffusion is the spontaneous movement of a substance down its concentration gradient, from a region where it is more concentrated to a region where it is less concentrated. Osmosis is the diffusion of water across a selectively permeable membrane.
The objective of this lab is to observe the different effects of diffusion and osmosis through different molarity solutions. Also, it helps understand the concept of how the separation of two solutions between a selectively permeable membrane could affect the weight of the dialysis bag.
If a dialysis bag containing the 15% glucose/ 1% starch solution is placed in a beaker of distilled water and iodine, then the iodine will enter through the dialysis bag to change the color.
If different molar solutions are put into dialysis bags and are immersed in beakers/cups of distilled water, then the water will go through the dialysis bags.
If potato cores or immersed in different molarity solutions, then the cores should increase in weight depending on each molarity of the solutions.
If NaCl surrounds the onion epidermis, then the cell should wilt or shrink in size.
Exercise 1A: This needs a 30-cm piece of 2.5 cm dialysis tubing soaked in water, 15 mL of the 15% glucose/1% starch, glucose Testape®, 250 mL beaker of distilled water, pipet string to tie ends of dialysis tubing, and 4 mL of Lugol’s solution.
Exercise 1B: This needs six 30 cm strips of presoaked dialysis tubing, string to tie ends of dialysis tubing, pipet, 25 mL of: distilled water, 0.2 M sucrose, 0.4 M sucrose, 0.6 M sucrose, 0.8 M sucrose, 1.0 M sucrose; scale, and six 250 mL cups filled with distilled water.
Exercise 1C: This needs a potato, cork borer, four 3 cm skinless potato cylinders, plastic wrap, paper towel, scale, six cups, 250 mL beaker, and 100 mL of: distilled water, 0.2 M sucrose, 0.4 M sucrose, 0.6 M sucrose, 0.8 M sucrose, 1.0 M sucrose.
Exercise 1D: This needs graph paper, pencil, calculator, and paper.
Exercise 1E: This needs a small piece of onion, 15% NaCl, cover slip, piece of paper towel, microscope slide, fresh water and a microscope.
Exercise 1A: First, soak a 30-cm piece of 2.5-cm dialysis tubing in a 250 mL beaker of water for a few minutes. Then, take it out and tie off one end of the tubing to form a bag. Put an extra fold at the end, twist, and tie it with string. Rub the end of the other end between fingers until it opens. Put 15 mL of the 15% glucose/1% starch solution in the bag. Use the glucose tape and dip it in the solution. Then, record the color change on the tape and the bag. Tie the other end of the bag with enough space for expansion. Fill a 250-mL beaker with distilled water. Add 4 mL of Lugol’s solution to the beaker and record the color change. Test the solution for glucose. Place the bag into the beaker. Wait 30 minutes to see the change of color in the bag or in the beaker. Finally, record the final color of the bag and beaker. Finally, test the liquid in the bag and beaker for any presence of glucose.
Exercise 1B: First, soak six 30-cm of dialysis tubing in water. Then, take each one out and tie a knot on one end of each piece to make a bag. Pour 25 mL of a different solution (distilled water, 0.2 M sucrose, 0.4 M sucrose, 0.6 M sucrose, 0.8 M sucrose, and 1.0 M sucrose) into separate bags. Tie the other end of the bag, leaving sufficient space for expansion. Record the initial mass for each bag in grams. Then, fill the cups with distilled water. Place each bag in one cup and label each cup with each solution. After 30 minutes, remove the bags from the water. Finally, record each bag...
Cited: AP Biology Diffusion & Osmosis Lab Packet
Campbell, Neil A., and Jane B. Reece. Biology. San Francisco: Pearson Benjamin Cummings, 2009. Print.
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