Chapter 5 - BSC 1010 Dr Presley Chapter 5 CELL MEMBRANES...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
BSC 1010 Dr. Presley 1 Chapter 5 CELL MEMBRANES - dynamic structures - outer living boundary of cell and intracellular compartments - provides cell shape and strength - regulates entry/exit of molecules, is selectively permeable - helps maintain cellular homeostasis - composition by weight: 50% phospholipid & 50% protein (some w/ attached sugars) - amphipathic = molecules have both hydrophobic and hydrophilic regions - chemical composition differs with membrane or location on a membrane - scientific progress on understanding the membrane: Study figures on page 139 - 1895 - Overton proposed membrane of lipids since lipids rapidly enter cells - 1917 - Langmuir - made a phospholipid memb., hydrophilic heads next to water - 1925 - Gorter & Grendel - suggested bilayer of phospholipids (RBC memb.) - 1935 - Danielli & Davson - Sandwich Model - phospholipid bilayer between layers of globular proteins - 1950's- Robertson --- Unit Membrane Model outer layer of proteins and polar heads of phospholipid, inner layer of nonpolar fatty acid tails of phospholipid, matched electron micrograph data -- all membranes in cells have same structure - 1972 - Singer & Nicolson ** Fluid-mosaic model = phospholipid bilayer with dispersed proteins Study Fig. 8.2 on page 139 FLUID-MOSAIC MODEL Study Fig. 8.6 on page 142 - phospholipid bilayer with dispersed proteins - Lipids provide for the following properties of the membrane: fluidity, structure, buoyancy for proteins, barrier, self-repairing phospholipids - major constituent, bilayer arrangement so that hydrophobic fatty acid tails extend into the middle of the membrane as they stabilize the membrane structure, hydrophilic phosphate groups face toward the watery environment or cytoplasm. Layers do not flip flops from inside to outside layers. Fluidity is lateral and can be rapid. Unsaturated fatty acids enhance fluidity. Proteins can drift more slowly in this layer. cholesterol - 25% of lipid composition of RBC membrane, 0% in other cells. May increase or decrease fluidity of membrane. - Proteins = mosaic pattern, provide the distinguishing characteristics of membrane - have polar and nonpolar regions, associations with lipids are not covalent - determine specific function of that part of the membrane - integral membrane proteins - only penetrate one side or completely cross the phospholipid layers(transmembrane proteins ). - peripheral membrane proteins - lack hydrophobic regions, not embedded in phospholipid layer, attached to exposed integral proteins or lipid groups - can drift laterally in the membrane, study hybrid cell proteins in Fig. 8.5, p.141 - some are attached to the cytoskeleton or extracellular matrix - asymmetrical - carbohydrate components restricted to exterior of membrane glycoproteins (for recognition), glycolipids - membranes with different function have different chemical make-up and structure - differences in cytoplasmic side and exterior side of membrane TYPES OF MEMBRANE PROTEINS Study Figure 8.9 on page 144 1. Transport proteins
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

Chapter 5 - BSC 1010 Dr Presley Chapter 5 CELL MEMBRANES...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online