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Transcript
Name: _________________ Date: ________ Composition of the Cell Membrane & Functions Per. ___ The cell membrane is also called the plasma membrane and is made of a phospholipid bilayer. The phospholipids have a hydrophilic (water attracting) head and two hydrophobic (water repelling) tails. The head of a phospholipid is made of an alcohol and phosphate group, while the tails are chains of fatty acids. Phospholipids can allow nonpolar molecules OR small molecules like water and oxygen to pass into or out of the cell. This is known as simple diffusion because it does not require energy and the water or molecules are moving with the concentration gradient. Concentration gradient- movement or spreading of molecules from a crowded area to a less crowded area. Some of the functions of the cell membrane include protecting and enclosing the cell, giving shape to the cell, allowing transportation of materials in and out of the cell, and carrying out metabolic reactions near the inner surface of the cell membrane. SKETCH AND LABEL a phospholipid coloring the heads red and the tails blue. label it (hydrophobic, hydrophilic, phosphate head, fatty acid tail, polar and non-polar) PHOSPHOLIPID Another type of lipid in the cell membrane is cholesterol that makes the membrane more fluid and adds to its flexibility. Embedded in the phospholipid bilayer are proteins that also aid in diffusion and in cell recognition. Large molecules like carbohydrates use transport proteins to help move across cell membranes. Transport proteins go all the way through the bilayer and so are called integral proteins. Peripheral proteins are found only on one side of the membrane and attach only temporarily, usually to aid with a reaction within the cell. Some of the membrane proteins have carbohydrate chains called glycoproteins, these proteins help with cell recognition. Some lipids also have carbohydrate chains attached and are glycolipids, these also help with cell recognition. Correctly color code and identify the name for each part of the cell membrane Letter Name/Color Letter _____ Phospholipid bilayer (no color) _____ _____ Integral protein (pink) _____ _____ Fatty acid tails (orange) _____ _____ Phosphate heads (yellow) _____ Name/Color Peripheral protein (red) Cholesterol (blue) Glycoprotein (green) Glycolipids (purple) Match the cell membrane structure or its function with the correct letter from the cell membrane diagram. See in the info on the first page for help. Letter Structure/Function Letter Structure/Function Attracts water _____ Repels water _____ _____ _____ _____ Helps maintain flexibility of membrane Involved in cell-to-cell recognition _____ Make up the two layers _____ Help transport certain materials across the cell membrane Also involved in cell to cell recognition Membrane Model Activity ANALYSIS 1. Why is the cell membrane described as being a bilayer?________________________________________ 2. What is a phospholipid?__________________________________________________________________ 3. What is the function of the cell membrane? _____________________________________________________________________________________ 4. Name three types of proteins embedded in the cell membrane and explain their function. _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ 5. Why do cells need energy to move some substances across the membrane? _____________________________________________________________________________________ _____________________________________________________________________________________ 6. When something moves with the concentration gradient it is called “passive transport”. Why do you think it is called passive transport? (Do you think this requires an input of energy?) _____________________________________________________________________________________ _____________________________________________________________________________________ 7. When something moves against the concentration gradient it is called “active transport”. Why do you think it is called active transport? (Do you think this requires an input of energy?) _____________________________________________________________________________________ _____________________________________________________________________________________ 8. What molecule provides the energy for Active Transport? ___________________________ 9. How would water move through the cell membrane (i.e. would it flow through or use a protein, and which protein would it use?) __________________________________________________________________ 10. How do you think large molecules like glucose move through the cell membrane? _________________