NYSED Part D Lab Review

1. NYSED Part D Lab Review Thanks to: Michael Comet South Lewis High School Turin, NY 13473

2. This lab is designed to help you understand the concepts of diffusion and osmosis and how these cell processes effect the cell • You should be able to define: diffusion, osmosis, hypertonic, isotonic, hypotonic, saline, selectively permeable, and understand the importance of molecular size Diffusion and Osmosis

3. Diffusion: the net movement of molecules from an area of high concentration to an area of low concentration along the concentration gradient. • Example is when you put your Lugol’s solution into the water and the water began to turn the “rust/tea” color. Diffusion Before diffusion occurs… After diffusion occurs…

4. Soak 20cm of dialysis tubing • Tie knot in one end • Put 20mL of glucose solution in and 20mL of starch solution in • Pinch/clamp closed and put into cellular environment (Lugol’s iodine and water) for 15 minutes • Observe the changes and infer what happened Wait about 15 minutes and observe. Insert into “cellular environment” Water and Part 1: Diffusion Through the Membrane of a “Cell” with glucose

5. What happened to the glucose in the “cell”? …the starch in the “cell”? …the Lugol’s iodine outside the “cell”? Why? S G G G I I S G I S G G I I S I Iodine solution (I) I After 15 minutes, observe… Glucose solution (G) I Starch solution (S) After 15 minutes… At the beginning…

6. Prepare a wet mount slide of the inner epidermis of a red onion section; • Observe the red onion and draw what you see; • Add a couple of drops of saline (salt) solution to the epidermis. Wait 5 minutes; • Observe under microscope again, note any changes; • Add freshwater to the slide, wait 5 minutes, observe changes again. Part 2 – Diffusion of Water Across a Membrane (Osmosis)

7. Before and after observations of red onion epidermis under the microscope (400X) Red Onion Plasmolysis Observation Red onion under in hypertonic (salt) solution. Note cell membrane has “withdrawn” and the cytoplasm has lost water to the salty environment, making it appear smaller and darker. Red onion under in isotonic (normal) solution. Note cell membrane and cytoplasm almost completely “fill” the boundary of the cell wall.