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Diffusion Experiment

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WEEK 3 EXPERIMENT ANSWER SHEET;Please submit to the Week 3 Experiment dropbox no later than Sunday midnight.;SUMMARY OF ACTIVITIES FOR WEEK 1 EXPERIMENT ASSIGNMENT;Experiment 3 Exercise 1 Diffusion: Movement of Solutes across a Membrane;Experiment 3 Exercise 2 Osmosis: Movement of Water across a Membrane;Experiment 3 Exercise 1: Diffusion - Movement of Solutes across a Membrane;We will be using dialysis tubing to simulate a semipermeable membrane. This tubing;allows small molecules (e.g., water, ions, glucose) to pass while preventing large;molecules (e.g., macromolecules like proteins, starch, glycogen) from moving across.;Be sure you have read over the suggested material before starting this exercise and;that you have reviewed the following animations;McGrawHill.2006.HowDiffusionWorks;https://highered.mcgraw;hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html;McGrawHill.2006.HowOsmosisWorks;https://highered.mcgraw;hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html;Experimental Design;A. The dialysis bag we will use is permeable to water and small molecules (e.g.;less than 500 g/mol) and impermeable to large molecules (e.g., more than 500;g/mol).;B. The dialysis bag is filled with a mixture of glucose (molecular weight = 180;g/mol) and protein (molecular weight = 10,000 g/mol) dissolved in water. A small;subsample of the dialysis bag contents is saved and will be used in Step 4.;C. The dialysis bag is then placed into a beaker of water. A small subsample of;beaker water is also saved and is to be used in Step 4 as well.;The presence or absence of glucose and protein will be determined using indicators.;Indicators change colors in the presence certain materials. The two tests that well use;are the Benedicts test for simple sugars (e.g., glucose) and the Biuret test for the;presence of proteins.;If glucose is present, the Benedicts indicator will turn green. If no glucose is;present, the solution will be blue.;If protein is present, the Biuret indicator will turn violet. If the solution remains;clear, then no protein is present.;D. The subsample of dialysis bag solution and the beaker water are tested for the;presence of glucose and protein. See Table 1 below for the results.;E. The dialysis bag is then left in the beaker of water for 60 minutes.;F. At the end of 60 minutes, the dialysis bag solution and the beaker water are;again tested for the presence of glucose and protein. See Table 1 below for the;results.;Table 1. Results of testing of the dialysis bag and beaker contents at the beginning and;end of the Experiment.;Test for Glucose;Test for Protein;Beginning;Dialysis Bag;Beaker;End;Beginning;End;Green;Green;Violet;Violet;Blue;Green;Clear;Clear;Questions;1. Summarize the results regarding the presence (+) or absence (-) of glucose and;protein in the dialysis bag and beaker in Table 2 below (4 pts);Table 2.;Glucose;Beginning;Protein;End;Beginning;End;Dialysis Bag;Beaker;2. Explain the movement or lack of movement of protein and glucose across the;dialysis bag membrane (4 pts);3. Which solution, that in the bag or that in the beaker, is hypotonic compared with;the protein solution (2 pts)?;4. What factors affect the movement of molecules across a semipermeable;membrane? Which factor plays the greatest role in biological systems (4 pts)?;5. Briefly explain what active transport is and how it differs from passive transport;especially in terms of concentration gradients (4 pts).;Experiment 3 Exercise 2: Osmosis - The Movement of Water across a Membrane;Before starting, lets see what you know about the terms hypotonic, isotonic and;hypertonic. Examine the diagrams below. Note that the small green circles represent;dissolved solutes like salt, glucose, and amino acids. You can assume that the;additional space surrounding the solutes is water and that the tan area is INSIDE the;cell.;Question;1. Define each term below in terms of solute concentration outside compared to the;inside of the cell. You do not need to explain which direction water will move (3 pts).;a. Hypotonic b. Isotonic c. Hypertonic Procedure;A. Open the following website to get started;TheBiologyPlace.NoDate.Osmosis:MovementofWateracrossMembranes;http://www.phschool.com/science/biology_place/biocoach/biomembrane1/osmosis.html;B. ReadovertheinformationpresentedandthenClick on;C. Then, Click on. Read through the information;presented and be sure to click on Animate beneath the illustration.;Questions;2. What concentration of salt is isotonic to animal cells (1 pts)?;3. When cells are in isotonic solution, is there movement of water into or out of the;cell? If so, describe this movement (3 pts).;Procedure (continued);D. Click on.;E. Read through the information presented and be sure to click on Animate;beneath the illustration. When ready, answer the following question.;Question;4. Describe the net movement of water molecules when cells are placed in a;hypotonic solution. Explain why water moves this way (3 pts).;Procedure (continued);F. Click on;G. Read through the information presented and be sure to click on Animate;beneath each of the illustrations. Answer the following questions. Your answers;should incorporate the terminology used in the animations.;Questions;5. What happens to an animal cell when placed in a hypotonic solution (2 pts)?;6. What happens to plant cells when placed in a hypotonic solution? What;accounts for the difference in outcomes between animal cells and plant cells (3;pts)?;Procedure (continued);H. Click on;I. Then, Click on. Read through the;information presented and be sure to click on Animate beneath the illustration.;Answer the following question.;Question;7. Describe the net movement of water molecules when cells are placed in a;hypertonic solution. Explain why water moves this way (3 pts).;Procedure (continued);J. Click on;K. Read through the information presented and be sure to click on Animate;beneath the illustration. Answer the following questions.;Questions;8. Compare and contrast what happens to plant and animal cells when placed in a;hypertonic solution. Be sure to use proper terminology (4 pts).;9. Based on what you learned in this exercise, explain why salt might make a good;weed killer (3 pts).;Week3ExperimentGradingRubric;Component;Expectation;Points;Experiment3;Exercise1;Interpretationofresultsanddemonstratedunderstandingof;18pts;diffusion(Table2andQuestions15).;Experiment3;Exercise2;Demonstratesunderstandingofisotonicsolutionsandnonet;7pts;movementofwater(Questions13).;Demonstratesunderstandingofhypotonicsolutionsandthe 8pts;movementofwater(Questions46).;Demonstratesunderstandingofhypertonicsolutionsandthe;10pts;movementofwater(Questions79).;TOTAL;43pts;Level of Detail: Only answer needed;Other Requirements: The number of questions are unimportant as long as the answers are in complete sentences.

 

Paper#15064 | Written in 18-Jul-2015

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