Osmosis & Diffusion In Depth

1. Osmosis & DiffusionIn Depth -Potato Lab

2. Review of Osmosis and Diffusion • Osmosis is the movement of water across a cell membrane from an area of higher concentration to an area of lower concentration. • Diffusion is the movement of molecules other than water across a membrane from an area of higher concentration to and area of lower concentration.

3. Water Potential

4. http://www.neosci.com/demos/10-1041_cell%20processes/Presentation.htmlhttp://www.neosci.com/demos/10-1041_cell%20processes/Presentation.html

5. Getting the Info! • Complete osmosis worksheet for background info! • Sodium/Potassium Pump and Osmosis… • http://nutrition.jbpub.com/resources/animations.cfm?id=27&debug=0 • Ion pumps worksheet!

6. Can a potato be used to demonstrate osmosis and diffusion? • Potatoes are composed of cells. • Potato cells have cell membranes. • Potato cells have some water and some salt inside the cells.

8. Design the Experiment (Discussion Questions) • What did we observe that would be evidence of osmosis and diffusion? • What did we measure to see if a change takes place? • What is the process that caused a change? • What was the variable? What was the control?

9. Materials • 2 Potato slices • 2 beakers • 1 teaspoon of salt • Water • Balance

10. Hypothesis and Method • Discuss a method with your group and formulate a hypothesis!

11. Sample Data Box Does osmosis explain the changes? Why?

12. Predictions • What do expect to see tomorrow? • What will each potato feel like on tomorrow? • What will each potato look like on tomorrow? • What will happen to the mass of each potato when you measure it tomorrow?

13. Extension…Sports Drinks! • Can you drink yourself to death?? • Should the tonicity of a fluid replacement drink be isotonic, hypertonic or hypotonic???

14. Hypernatremia • Certain conditions may result in a decrease in the sodium concentration in interstitial fluid. For instance, during sweating the skin excretes sodium as well as water. If we replace the lost fluid with plain water then we may produce a sodium deficit. The decrease in sodium concentration in the interstitial fluid lowers the interstitial fluid osmotic pressure and establishes an effective water concentration between the interstitial fluid and the intracellular fluid. Water moves from the interstitial fluid into the cells, producing two results that can be quite serious: • The first result, an increase in intracellular water concentration, called over hydration which disrupts nerve cell function. In severe over hydration we may see disoriented behaviour, convulsions, coma, and even death • The second result is a loss of interstitial fluid volume that leads to a decrease in the interstitial fluid pressure. As the pressure drops, water moves out of the plasma, resulting in a loss of blood volume that may lead to circulatory shock.

15. Sports Drinks!

16. Isotonic - quickly replaces fluids lost by sweating and supplies a boost of carbohydrate. This drink is the choice for most athletes - middle and long distance running or team sports. Glucose is the body's preferred source of energy therefore it may be appropriate to consume Isotonic drinks where the carbohydrate source is glucose in a concentration of 6% to 8% - e.g. High Five, SiS Go, Boots Isotonic, Lucozade Sport. • Hypotonic - quickly replaces fluids lost by sweating. Suitable for athletes who need fluid without the boost of carbohydrate e.g. jockeys and gymnasts. • Hypertonic - used to supplement daily carbohydrate intake normally after exercise to top up muscle glycogen stores. In ultra distance events, high levels of energy are required and Hypertonic drinks can be taken during exercise to meet the energy demands. If used during exercise Hypertonic drinks need to be used in conjunction with Isotonic drinks to replace fluids.

17. Want to make your own? • Isotonic - 200ml of orange squash (concentrated orange), 1 litre of water and a pinch of salt (1g). Mix all the ingredients together and keep chilled • Hypotonic - 100ml of orange squash (concentrated orange), 1 litre of water and a pinch of salt (1g). Mix all the ingredients together and keep chilled. • Hypertonic - 400ml of orange squash (concentrated orange), 1 litre of water and a pinch of salt (1g). Mix all the ingredients together and keep chilled.