| In and Out of Cells |
| Students have been introduced to the four processes (diffusion, etc.) in the Molecule Movement lesson. In this lesson, students have a chance to personalize the information they are given about those processes. They are given a brief summary of each process (see below) and are assigned work closely related to the summaries. The assignment is that the students will create either a diagram or an analogy for each process that shows all the aspects of each process as described on the handout: In and Out of Cells 1) Diffusion: The movement of molecules from where they are in high concentration to where they are in low concentration. Example: You can smell perfume or cologne on another person because the molecules of the scent diffuse from the person (high concentration) to your nose (low concentration). 2) Active Transport: Proteins in the membrane pump specific molecules in one direction so that concentration of that molecule becomes higher either inside or outside the cell. We call it active because it must overcome diffusion, which works to balance concentrations. Example of Active Transport: Proteins in a cell membrane pump waste molecules out of the cell. The waste molecules slowly diffuse back in, so the membrane proteins have to work hard to keep pumping them out. * Think of being in a canoe in the middle of a lake, and having water seeping into the boat through cracks in the bottom. In order to survive, you must actively scoop or pump water out. 3) Passive transport: Proteins in the membrane provide a way for specific molecules to get through the membrane. The molecules can go into or out of the cell using those proteins. We call it passive because it lets diffusion be in charge of where the molecules go. * Think of a two-way street with a sign that says �No Trucks.� Cars can go both up and down the street, but trucks aren�t permitted at all. 4) Osmosis: The movement of water molecules through a selectively permeable membrane from where they are in high concentration to where they are in low concentration. * Think of a dry sponge that is put into a bucket of water. The sponge had a low concentration of water and the bucket had a high concentration of water, so water will flow into the sponge. For each of the above (1-4), either draw diagrams that represent the process or give an example of it. You may not use the examples given above. Do this on a separate sheet of paper. |