Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Chapter 7 - Membrane structure and function. In this chapter you will learn: Define the following terms: amphipathic molecules, aquaporins, diffusion; explain how membrane fluidity is influenced by temperature and membrane composition; distinguish between the following pairs or sets of terms: peripheral and integral membrane proteins, channel and carrier proteins, osmosis, facilitated diffusion, and active transport, hypertonic, hypotonic, and isotonic solutions. | Chapter 7 Membrane Structure and Function Overview: Life at the Edge The plasma membrane is the boundary that separates the living cell from its surroundings. The plasma membrane exhibits selective permeability, allowing some substances to cross it more easily than others. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cellular membranes are fluid mosaics of lipids and proteins Phospholipids are the most abundant lipid in the plasma membrane Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings For the Cell Biology Video Structure of the Cell Membrane, go to Animation and Video Files. Phospholipids: Amphipathic Molecules Hydrophilic head WATER Hydrophobic tail WATER Figure 7.2 Phospholipid bilayer (cross section) In 1935, Hugh Davson and James Danielli proposed a sandwich model in which the phospholipid bilayer lies between two layers of globular proteins. Later studies found problems with this model, particularly the placement of membrane proteins, which have hydrophilic and hydrophobic regions. In 1972, J. Singer and G. Nicolson proposed that the membrane is a mosaic of proteins dispersed within the bilayer, with only the hydrophilic regions exposed to water. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein The Fluid Mosaic Model Singer and Nicholson: Figure 7.3 The fluid mosaic model for membranes Freeze-fracture studies of the plasma membrane supported the fluid mosaic model. Freeze-fracture is a specialized preparation technique that splits a membrane along the middle of the phospholipid bilayer. Copyright © 2008 Pearson Education, Inc., publishing as . | Chapter 7 Membrane Structure and Function Overview: Life at the Edge The plasma membrane is the boundary that separates the living cell from its surroundings. The plasma membrane exhibits selective permeability, allowing some substances to cross it more easily than others. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cellular membranes are fluid mosaics of lipids and proteins Phospholipids are the most abundant lipid in the plasma membrane Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings For the Cell Biology Video Structure of the Cell Membrane, go to Animation and Video Files. Phospholipids: Amphipathic Molecules Hydrophilic head WATER Hydrophobic tail WATER Figure 7.2 Phospholipid bilayer (cross
