Questions for Lab – Diffusion – Experiment 1: Diffusion Through a


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Questions for Lab – Diffusion – Experiment 1: Diffusion Through a Liquid: 1. A concentration gradient affects the direction that solutes diffuse. Describe how molecules move with respect to the concentration. 2. How does the size of a solute affect the rate of diffusion? 3. Does polarity affect the rate of diffusion? Explain your answer using the structure of a cell membrane as an example. 4. Record your hypothesis from Step 3 of this experiment. 5. Which dye diffused the fastest in corn syrup? 6. Does the rate of diffusion correspond with the molecular weight of the dye? 7. Does the rate of diffusion change over time? Why or why not? 8. Cells receive vital nutrients and rid toxic waste with the help of the circulatory system. What is the critical distance a cell must maintain from a capillary (the point of nutrient/waste exchange) in order to survive? Explain the role diffusion plays in this process. Questions for Lab – Diffusion – Experiment 2: Concentration Gradients and Membrane Permeability: 1. Why is it necessary to have positive and negative controls for the indicators in this experiment? 2. List your results for the positive and negative controls for the indicators: Starch positive control color: Starch negative control color: Glucose positive control color: Glucose negative control color: 3. Which substance crossed the dialysis membrane? What evidence from your results proves this? 4. What molecules remained inside of the dialysis bag? What evidence from your results proves this? 5. Of the substances that diffused through the bag, did all of the molecules of that substance diffuse through? 6. Starch is a very large molecule made up of many glucose molecules bonded together. Does this help explain the results of this experiment? Explain how. 7. Explain the significance of what you learned about diffusion across a semi-permeable membrane for one of the cells in your body. Can all substances move in or out of the cell the same way? (Think about what you previously learned about membrane structure.)

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