APB Big Idea 2: Diffusion and Osmosis Lab. In your Lab Notebook

Transcription

1 APB Big Idea 2: Diffusion and Osmosis Lab In your Lab Notebook

2 Part 1. Rate of Diffusion I. Purpose Baseline model for investigating the relationship between the volume and surface area of a model cell and the rate of diffusion II.Pre-Lab question(s) The phenolphthalein-agar model cells are initially pink. a. Predict the observation when these cells are placed in dilute hydrochloric acid assuming hydronium ions are able to diffuse into the agar. b. How can these observations be used to measure the rate of diffusion? III.Materials 1M HCl Phenolphthalein-agar block.1m NaOH Beaker Metric ruler Plastic knife Plastic spoon IV.Procedure A. Baseline 1. Cut a 2-cm agar cube 2. Pour 100mL into a beaker 3. Place the agar cube into the HCl 4. Gently agitate 5. After 10 minutes, remove the cube 6. Cut the cube and measure the depth the acid penetrated the cube 7. Record results B. Inquiry 1. Design a controlled experiment to investigate the effects of surface area and cell volume on the rate of diffusion in agar model cells. 2. Graph it if you can!

3 V. Results Baseline Cube Surface area Volume SA to Vol Ratio Diffusion Depth Diffusion Rate VI. Conclusion 1st paragraph: Restate the purpose of the INQUIRY part of the investigation 2nd paragraph: Make a CLAIM and support it with specific, relevant EVIDENCE you collected. In the same paragraph, include your REASONING. Reasoning illustrates why particular evidence is the most relevant evidence to use in support of a particular claim. Reasoning typically includes describing the scientific knowledge or principle, that applies to a particular claim and evidence. Make sure you show the logic that leads from the evidence to the claim. 3rd paragraph: Discuss any ERRORS that may have impacted data collection and/or analysis. Discuss any recommendations for FUTURE labs or extensions. 4th Paragraph: Relate this lab to the THEME of structure and function in Biology. How is the cell specially designed to selectively transport materials in and out of the cell? Why is this important in living things? Provide specific examples.

4 Part 2. Modeling Cell Transport I. Purpose Constructing model cells to compare the net movement of material in solutions that are hypotonic, hypertonic, and isotonic. II. Pre-Lab question(s) 1. Consider this: An artificial membrane that is selectively permeable encloses an aqueous solution. The solution surrounding the model cell contains a different aqueous solution. Assume that monosaccharides such as glucose and fructose are able to cross the membrane but that larger disaccharides, such as sucrose, do not. The exact concentration of each solute in the cell and surroundings are shown. a. Which solute(s) will exhibit a net diffusion into the cell? b. Which solute(s) will exhibit net diffusion out of the cell? c. With respect to glucose, is the surrounding environment hypertonic or hypotonic to the cell? 2. Review the possible solutions listed below: 5% Albumin 1M Glucose 1M Sodium Chloride 1M Sucrose Water a. Using these materials, select 4 different pairs of solutions, including water, to study in the Baseline Activity. One solution of each pair will go inside a model cell, and the other solution will be placed in the surrounding environment. Enter your choices in the table below. b. What is the purpose of Trial 5 with water in both compartment? c. Using your knowledge of gradients and the permeability of the membrane, predict whether there will be net diffusion of water by osmosis into or out of each model cell. Enter your prediction in the table.

5 Trial # Model cell (in dialysis bag) Surrounding environment (in cup) Predicted Net diffusion (into or out of cell) water water III.Materials 5% solution of albumin 1M Glucose 1M NaCl 1M Sucrose Water Balance Plastic cups Dialysis tubing Graduated cylinder IV. Procedure A. Baseline 1. Obtain 5 plastic cups and label them Obtain 5, pre-soaked dialysis tubes 3. Fill the dialysis tube with the specified solutions listed from your pre-lab question 4. Tie the dialysis tube securely 5. Rinse with distilled water and pat dry 6. Record initial mass 7. Fill cups with 100mL of designated solutions from your pre-lab question 8. Place dialysis bags into designated solutions 9. Record final mass after 20 minutes 10. Determine the percent change in mass for each model cell B. Inquiry 1. Design a controlled experiment to investigate a variable that might affect the exchange of nutrients between a model dialysis cell and its surrounding environment. 2. Graph it if you can!

6 V. Results Baseline Trial Model Cell Environment Prediction % Change in Mass VI. Conclusion 1st paragraph: Restate the purpose of the INQUIRY part of the investigation 2nd paragraph: Make a CLAIM and support it with specific, relevant EVIDENCE you collected. In the same paragraph, include your REASONING. Reasoning illustrates why particular evidence is the most relevant evidence to use in support of a particular claim. Reasoning typically includes describing the scientific knowledge or principle, that applies to a particular claim and evidence. Make sure you show the logic that leads from the evidence to the claim. 3rd paragraph: Discuss any ERRORS that may have impacted data collection and/or analysis. Discuss any recommendations for FUTURE labs or extensions. 4th Paragraph: Relate this lab to the THEME of structure and function in Biology. How is the cell membrane specially designed to selectively transport materials in and out of the cell? Why is this important in living things? Provide specific examples.