IB 1108 L07 Osmosis-2

Pre-Lab Questions What is the water potential of an open beaker containing pure water? Why don’t red blood cells swell or shrink in blood? How do osmotic power plants work? Research the structures that protect plant and animal cells from damage resulting from osmotic pressure. Write a few paragraphs explaining what they are, how they work, and where they are located. Experiment 1: Tonicity and the Animal Cell Hypothesis Data Data Tables Table 1: Osmosis Results Solution Type Volume (mL) Before Osmosis Volume (mL) After Osmosis 100% Distilled Water 100% Corn Syrup 10% Corn Syrup/90% Distilled Water Control Table 2: Observations of Eggs After Osmosis 100% Distilled Water 100% Corn Syrup 10% Corn Syrup/ 90% Distilled Water Control Post-Lab Questions Record your hypothesis from Step 15 here. Be sure to include scientific reasoning to support your predictions. How do each of the three eggs placed in solution compare to the control egg? For each beaker, identify whether the solution inside was hypotonic, hypertonic, or isotonic in comparison to the control beaker. What was the direction of osmosis in the beaker labeled “100% distilled water”? Did the egg in this beaker burst? Was there any liquid in the “control” beaker after 24-48 hours? If so, why do you think this is? If not, why do you think this is? Which solution contained a dehydrated cell? Think about someone with a high sugar diet. Hypothesize how their cells might be affected by osmosis. Experiment 2: Tonicity and the Plant Cell Data Tables Table 3: Water Displacement per Potato Sample Potato Type Potato Observations Sample Initial Displacement (mL) Final Displacement (mL) Net Displacement (mL) A B A B Post-Lab Questions How did the physical characteristics of the potato vary before and after the experiment? Did it vary by potato type? What does the net change in the potato sample indicate? Different types of potatoes have varying natural sugar concentrations. Explain how this may influence the water potential of each type of potato. Based on the data from this experiment, hypothesize which potato has the highest natural sugar concentration. Explain your reasoning. Did water flow into or out of the plant cells (potato cells) in each of the samples examined? How do you know this? Would this experiment work with other plant cells? What about with animal cells? Why or why not? From what you know of tonicity, what can you say about the plant cells and the solutions in the test tubes? What do your results show about the concentration of the cytoplasm in the potato cells at the start of the experiment? If the potato is allowed to dehydrate by sitting in open air, would the potato cells be more likely to absorb more or less water? Explain.