Chapter 8 Membrane Structure and Function Plasma Membrane
Chapter 8 Membrane Structure and Function
Plasma Membrane
Membrane Composition u. Question: How are the materials arranged?
Lipid Bilayer u. Phospholipids u. Hydrophilic heads u. Hydrophobic tails
Membrane Models
Davson-Danielli Model 1935 u. Lipid bilayer. u. Proteins coat the surfaces. u. Sometimes called the “sandwich” model.
Evidence u. Biochemical work. u. TEM pictures show the membrane as a double line.
Problems u. Not all membranes in a cell were the same. u. How could the proteins stay in place? u. Result - the model was questioned and tested by scientific process.
Fluid Mosaic Model 1972 u. New model to fit the new evidence with membranes. u. Example of “Science as a Process”.
Fluid Mosaic Model
“Fluid”
Ways to keep the membrane “fluid”
“Mosaic”
Evidence u. TEM pictures of fractured membranes. u. Cell fusion studies. u. Tagging of membrane proteins by antibodies.
Protein Function in Membranes
Types of Membrane Proteins u. Integral – u. Peripheral -
Question? u. How do the integral proteins stick to the membrane?
Hydrophilic Amino Acids Hydrophobic Amino Acids Hydrophilic Amino Acids
Membranes are Bifacial
Carbohydrates
Membrane Carbohydrates
Question u. How do materials get across a cell's membrane?
Problems u. Lipid bilayer is hydrophobic. Hydrophilic materials don't cross easily. u. Large molecules don't cross easily. Too big to get through the membrane.
Mechanisms 1. 2.
Passive Transport
Types of Passive Transport 1. 2. 3.
Diffusion
Equilibrium
Factors that Effect Diffusion 1.
Osmosis
Tonicity
Isotonic
Hypotonic
Hypertonic u.
Facilitated Diffusion
Aquaporins u. Newly found channels for osmosis. GFP labeled Aquaporins
Active Transport
Types of Active Transport 1.
Carrier-Mediated Transport
Examples 1.
+ Na - + K pump
Electrogenic or H+ pumps u.
Cotransport
Exocytosis
Endocytosis u.
Types 1.
Carbohydrates
Forming vesicles
Summary u. Know membrane structure. u. Be able to discuss the various methods by which cells move materials through membranes. u. Be able to solve problems in osmosis.
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