1. Diffusion of Water through a Membrane

2. Review Cell make up all living things. Red Onions

3. Review Diffusion is when molecules move from HIGH to LOW concentration

4. Part 2: Red Onion Cells and Osmosis Osmosis is the diffusion of water molecules. Water molecules diffuse by osmosis all the time. Cytoplasm = 80% water. Tap water = 80% water. Distilled water = 100% water. Salt water = (65%). Water molecules diffuse by osmosis all the time. Cytoplasm = 80% water. Tap water = 80% water. Distilled water = 100% water. Salt water = (65%).

5. Red Onion Cells

6. Turn to Question 6 on Page 7. Sketch a picture of the Red Onion Cells in TAP WATER. cell wall cytoplasm cell membrane Red Onion Cells in Tap Water Sketch the cells and label the cell membrane, cell wall, and cytoplasm.

7. Diffusion Through a Membrane cytoplasm cell wall cell membrane Turn to Question 10 on Page 7. Sketch a picture of the Red Onion Cells in SALT WATER. Red Onion Cells in Salt Water Sketch the cells and label the cell membrane, cell wall, and cytoplasm.

8. Describe the changes you observed (saw) in the red onion cells after they were placed in SALT WATER. What happened to the cells? Turn to Question 8 on Page 7.

9. #11 – Describe what happened to the amount of water in the onion cells when they were placed in SALT WATER. Did the water diffuse INSIDE or OUTSIDE of the cell? Was there MORE or LESS water in the cell? Turn to Page 8. Answer question #11.

10. Diffusion Through a Membrane cell wall cytoplasm cell membrane Turn to Question 15 on Page 8. Sketch a picture of the Red Onion Cells in DISTILLED WATER. Red Onion Cells in Distilled Water Sketch the cells and label the cell membrane, cell wall, and cytoplasm.

11. #13 – Describe what happened to the onion cells after you placed them in DISTILLED WATER. Turn to Question 13 on Page 8.

12. Look at the Analysis Question 1 on Page 8. Imagine that a group of students was not listening to directions at the beginning of the diffusion experiment. They were supposed to put starch into the plastic “cell” and starch indicator in the beaker. Instead, they put starch indicator into the “cell” and starch in the beaker. Say how their results would be different from the rest of the class. How would the teacher know they hadn’t listened to directions?

13. You will receive (get) a handout with these questions written in plain English. You will write your answers IN THE LAB PACKET. You may work with a partner as long as you are focusing on the questions. Look at the Analysis Questions on Pages 8-9.