TAILIEUCHUNG - Lecture Biology - Chapter 5: The dynamic cell membrane

Chapter 5 - The dynamic cell membrane. In this chapter, we will address the following questions: What is the structure of a biological membrane? How is the plasma membrane involved in cell adhesion and recognition? What are the passive processes of membrane transport? How do substances cross membranes against a concentration gradient? How do large molecules enter and leave a cell? What are some other functions of membranes? | The Dynamic Cell Membrane 5 The Dynamic Cell Membrane What Is the Structure of a Biological Membrane? How Is the Plasma Membrane Involved in Cell Adhesion and Recognition? What Are the Passive Processes of Membrane Transport? How Do Substances Cross Membranes Against a Concentration Gradient? How Do Large Molecules Enter and Leave a Cell? What Are Some Other Functions of Membranes? What Is the Structure of a Biological Membrane? The general structure of membranes is know as the fluid mosaic model. The phospholipid bilayer is like a “lake” in which a variety of proteins “float.” Figure The Fluid Mosaic Model Figure Phospholipids (A) Repeat Fig here Figure A Phospholipid Bilayer Separates Two Aqueous Regions What Is the Structure of a Biological Membrane? Artificial bilayers can be made in the laboratory. Lipids maintain a bilayer organization spontaneously—helps membranes fuse during phagocytosis, vesicle formation, etc. What Is the Structure of a Biological Membrane? Membranes may vary in lipid composition Phospholipids vary—fatty acid chain length, degree of saturation, phosphate groups Membranes may be up to 25 percent cholesterol What Is the Structure of a Biological Membrane? Phospholipid bilayer is flexible, and the interior is fluid, allowing lateral movement of molecules. Fluidity depends on temperature and lipid composition. What Is the Structure of a Biological Membrane? Membranes contain proteins, the number of proteins varies with cell function Some membrane proteins extend across the lipid bilayer—with hydrophobic and hydrophilic regions or domains. Figure Membrane Proteins Revealed by the Freeze-Fracture Technique What Is the Structure of a Biological Membrane? The proteins and lipids in the membrane are independent and only interact noncovalently. What Is the Structure of a Biological Membrane? Two types of membrane proteins: Integral membrane proteins span the bilayer, .

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