Build-A-Membrane. Print-and-Go. Name Date

Transcription

1 Name Date Print-and-Go Build-A-Membrane Cell membranes are made of phospholipid molecules that arrange themselves into two rows called a bilayer. s are embedded in the phospholipid bilayer, through one or both layers. These proteins help other molecules cross the membrane and perform a variety of other functions. Create a model of a small section of cell membrane by following the instructions below. 1. Cut out the phospholipid bilayer (page S2) along the solid lines. s of the paper in the direction of the arrows. 2. Fold the phospholipid bilayer along the dotted lines and tape the edges together to form a fully enclosed rectangular box. 3. Cut out each protein (pages S3 and S4) along the solid black lines and fold along the dotted lines. 4. Form a 3-D shape by joining the protein sides and tops together and tape them in to place. Use the tabs to help you. 5. Tape the 3-D proteins into place along the edges of the phospholipid bilayer. 6. By staggering the transmembrane proteins back and forth along both long sides of the bilayer box, the whole model will stand up by itself on a table University of Utah Permission granted for classroom use. S1

2 Phospholipid Bilayer Fold along dotted lines. S2

3 2008 University of Utah Permission granted for classroom use. S3 Channel (half) Receptor Cut-outs Print-and-Go

4 2008 University of Utah Permission granted for classroom use. S4 Transporter Tethered Anchored Cut-outs Print-and-Go

5 Name: Hour: Cell Membranes The cell membrane regulates what enters and leaves the cell. It also aids in the protection and support of the cell. In a way, the cell membrane is similar to the walls that surround your house. As these walls help to protect your house from what is outside, so does the cell membrane by sealing off the cell from the outside environment. But if you lived in the house, you would still want to receive messages, fuel, and power from the outside environment. So utilities lines like telephone, gas, and electric would have to be able to pass through the walls of your house. You would also like to bring in food and take out trash, thus doors would be needed. The needs of the cell are similar. It must communicate with other cells, take in food and water, and eliminate waste. All of these processes take place through the cell membrane. The cell membrane is composed of several kinds of molecules. The most important of these are lipids. A double layer, bilayer, of lipid molecules forms the basic unit from which cell membranes are constructed. The lipids in the cell membrane are a special type of lipid called phospholipid. They have a phosphate head and a lipid tale region. The head is hydrophilic (water loving) and the tail is hydrophobic (water fearing). This is one of the reasons why some molecules easily pass though the cell membrane (O2, CO2, and steroids) and others with difficulty (carbohydrates, proteins, nucleic acids)). s and carbohydrates are also associated with the cell membrane. Some proteins stick to the surface of the lipid bilayer, whereas other span the membrane from one side to the other and are free to move around with in the membrane. Where proteins are located in the lipid bilayer are dependent on their molecular structure (shape). Some of the freemoving proteins serve as transport proteins, activing like channels or tunnels through which molecules may pass. Other proteins act like small pumps, actively pushing molecules from one side of the membrane to the other, like a revolving door. The carbohydrates are attached to either protein (glycoprotein) or lipid (glycolipid). These carbohydrates attached to proteins or lipids act like recognition sites identifying tags and allow cells to recognize other cells from the same organism. As a result of the structure, the cell membrane is often described as the Fluid Mosaic Model. The word fluid refers to the idea that the membrane is actually moving at an extremely slow rate. The mosaic refers to the idea that the membrane is like a collage of proteins and other molecules embedded in the fluid matrix, much like different color tiles embedded in grout in a ceramic mural.

6 Name: Hour: Summary Questions Answer in complete sentences. 1. What are the functions of the cell membrane? 2. The cell membrane is often described as a bilayer. Explain this term. What two layers make up the cell membrane? 3. Where are proteins found in the cell membrane? 4. Explain why the cell membrane is described as a Fluid Mosaic Model. 5. Give an example of a molecule that is unable to pass through the cell membrane. Explain why it is unable to pass through. 6. Explain the function of a transport protein. 7. What is one possible message that one cell might send to another cell? 8. Explain the reason why an organ can be rejected after a transplant.