CELL MEMBRANE STRUCTURE & FUNCTION page 206 How do the structures of the cell membrane help it function?

Read quietly and independently*. Music is ok! Please RECORD INFORMATION on these sections …….(and use complete sentences!) PART I – MOLECULAR BUILDING BLOCKS OF CELLS AND THE CELL MEMBRANE. PART 2 – THE CELL MEMBRANE CONTROLS WHAT ENTERS AND LEAVES THE CELL

READING STRATEGIES TO USE…. Read the section first, then answer the questions. Use post-it notes to record important ideas, definitions, questions you might have as you read. Read the questions, then read the entire section, then answer the questions. Read first with a partner, then answer the questions*. ABOVE ALL…..avoid reading merely to answer the questions. Don’t ignore the rest of the assigned reading! AND…don’t copy down information that you don’t understand!!!

PART I – MOLECULAR BUILDING BLOCKS OF CELLS AND THE CELL MEMBRANE. 1. Carbohydrates, lipids, proteins and nucleic acids are the macromolecules (large molecules) that make up cells. 2. The cell membrane, in particular, is made up of lipids and proteins. 3. The lipids in a cell membrane are called phosopholipids 4. Sketch a portion of a cell membrane. 5. Because phospholipids are both attracted to water and repelled by water they form a lipid bilayer that acts as a barrier 6. Imbedded in the lipid bilayer are different proteins. Give the function of each listed below. Use a specific example and sketch wherever possible. Channel proteins allow molecules in and out Proteins with carbohydrate “flags” identifiers Receptor proteins receive things like hormones that trigger a response Protein pumps. actively move things across from low to high

PART 2 – THE CELL MEMBRANE CONTROLS WHAT ENTERS AND LEAVES THE CELL 1. The cell membrane is semi permeable or selectively permeable This means that only some things can pass through it. 2. Size, charge and shape determine whether a molecule can pass through the cell membrane. 3. Substances will move across the cell membrane by diffusion They will naturally move from areas of high concentration to areas of low concentration. 4. When water diffuses across a membrane it is called osmosis. 5. Both diffusion and osmosis require NO output of energy from the cell.

PART 2 – THE CELL MEMBRANE CONTROLS WHAT ENTERS AND LEAVES THE CELL, CONTINUED 6. Some molecules are too big or have a charge and must move through a protein channel. 7. When these molecules move from high to low concentration, no energy from the cell is required. This movement is called passive transport 8. Sometimes the cell must use a protein to pump things into or out of the cell from LOW to HIGH concentration. The cell must use energy in the form of ATP This movement is called active transport. 9. Endocytosis and exocytosis both require the cell to use energy. Make a labeled sketch of each of these processes. In your own words, describe what is happening in each sketch.