1. Chapter 2, Section 2 The Cell in Its Environment Monday, October 5, 2009 Pages 56 -- 60

2. Objectives Describe the three methods by which materials move into and out of cells. Compare passive transport to active transport. Explain why cells are small.

3. Vocabulary Words Selectively permeable Diffusion Osmosis Passive transport Active transport

4. Diffusion Demo Think about the following as you observe the demonstration: Why did the water in the bag turn purple? Why didn’t the water in the cup turn purple?

5. Gatekeeper The cell membrane serves as a gatekeeper. Some substances are allowed in while others are kept out. Substances move into and out of a cell through one of these three methods: Diffusion Osmosis Active transport

6. Diffusion It is the process by which molecules move from a higher concentration to a lower concentration. What causes diffusion and how does it work?

7. Osmosis Osmosis is the diffusion of water molecules through a selectively permeable membrane. Normal shape of red blood cell. Cell has shrunk because water has moved out by osmosis. Cell is swollen with water that is moved in by osmosis.

8. Active Transport Active transport requires the use of energy to move materials through a cell membrane. Passive transport does not require the use of energy.

9. Active Transport Proteins These are also known as ATPs. Their role is to “pick-up” molecules outside the cell and carry them in using energy. Calcium, potassium, and sodium are examples of molecules that must be carried in.

10. Engulfing Engulfing is another form of active transport.

11. Why are cells so small? Think about the organization of organelles within the cell. Think about the cytoplasm.

12. Homework Workbook 2.2 -- Due on Wednesday, 10/7. Vocabulary Quiz--Sections 1 and 2 on Wednesday, 10/7. REMINDER: Lab write-up due on Tuesday, 10/6.