5/18 Science Starter Imagine you are in a shoe store that is selling your favorite pair of shoes, along with 100 other people in the store looking for the same shoes! Across the way there is another shoe store selling the same shoes with only 10 people in the store. What do you do and why?

Predict Observe Explain (P. O Predict Observe Explain (P.O.E) Predict: If I soaked potato slices in salt water and other slices in plain water, what will happen to the slices? Be as descriptive as possible Observe: What did you see? Be as descriptive as possible. Explain: Why did that occur? Using scientific language

Unit: Cells Lesson: Osmosis Overarching goal: Structure and Function Systems of specialized cells within organisms help them perform the essential functions of life. (HS-LS1-1) Today’s Stepping Stone: Students will understand how cells gain and lose water through their semi-permeable membranes. Toppen 2015

Why does the water move into or out of the potato cells Why does the water move into or out of the potato cells? The water molecules move from an area of: high water concentration to an area of low water concentration. Just like if you were in that crowded shoe store, you would have moved to the less crowded shoe store. Only certain things can pass though, usually only small molecules like water

Why does the water move into or out of the potato cells? In plain water: water molecules outside the cells were too crowded and went inside the cells because there were less water molecules there, swelling the cells and making the potato feel more rigid. In salt water: water molecules were too crowded in the cells compared to outside the cells so water went out of the cells into the salt water, shriveling the cells and making the potato feel limp. Water “sucked” out Water “pumped” in Potato in Salt water Potato in plain water

Group Challenge! Your group works for a Blood Bank and is in charge of storage. Fortunately you have received a high volume of blood from many donors in the Chula Vista community. In order to safely store the blood cells you must put them in a solution, there are three options to choose from. Hypotonic solution (diluted solution of salts) Hypertonic solution (very concentrated solution of salts) Isotonic solution (same level of salts as blood cells) Type an explanation for which solution your group chooses and why? What would happen to the blood cells in the other two solutions?

Group Challenge 2! In your groups come up with a scientific argument about why is it good to stay hydrated and drink plenty of water, and to avoid very salty foods. Include academic language: high concentration low concentration semipermeable membrane Be prepared to present to the class.

OSMOSIS AND MEDICINE Osmosis has several implications where medical care is concerned, particularly in the case of the storage of vitally important red blood cells. These are normally kept in a plasma solution which is isotonic to the cells when it contains specific proportions of salts and proteins. However, if red blood cells are placed in a hypotonic solution, or one with a lower solute concentration than in the cells themselves, this can be highly detrimental. Hence water, a life-giving and life-preserving substance in most cases, is a killer in this context. If red blood cells were stored in pure water, osmosis would draw the water into the cells, causing them to swell and eventually burst. Similarly, if the cells were placed in a solution with a higher solute concentration, or hypertonic solution, osmosis would draw water out of the cells until they shriveled. In fact, the plasma solution used by most hospitals for storing red blood cells is slightly hypertonic relative to the cells, to prevent them from drawing in water and bursting. Physicians use a similar solution when injecting a drug intravenously into a patient. The active ingredient of the drug has to be suspended in some kind of medium, but water would be detrimental for the reasons discussed above, so instead the doctor uses a saline solution that is slightly hypertonic to the patient's red blood cells. One vital process closely linked to osmosis is dialysis, which is critical to the survival of many victims of kidney diseases. Dialysis is the process by which an artificial kidney machine removes waste products from a patients' blood—performing the role of a healthy, normally functioning kidney. The openings in the dialyzing membrane are such that not only water, but salts and other waste dissolved in the blood, pass through to a surrounding tank of distilled water. The red blood cells, on the other hand, are too large to enter the dialyzing membrane, so they return to the patient's body. Read more: http://www.scienceclarified.com/everyday/Real-Life-Chemistry-Vol-2/Osmosis-Real-life- applications.html#ixzz3a9FKGpHI