2010 Bio 317 Lecture 2

2010 Bio 317 Lecture 2 - 1 Prof. William Collins OfFce: 534...

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Unformatted text preview: 1 Prof. William Collins OfFce: 534 Life Sciences Building OfFce Hours: Mondays, 4:00 – 5:00 PM or by appointment Recommended Reading: Matthews, Chapters 2 & 3 BIO 317: Lecture 2 The Shape and Amphipathic Nature of Phospholipids Gives Them Unique Properties Phospholipids spontaneously form bilayers in an aqueous solution. Phospholipid bilayers spontaneously close to form sealed compartments. Phospholipid bilayers have a self-healing property. 2 Lipid Molecules Diffuse Freely Within Lipid Bilayers Lipids exhibit rapid movement (e.g., rotation, lateral diffusion) within a monolayer (“lea¡et”). However, lipid molecules rarely “¡ip-¡op” from one lea¡et to the other. Thus, lipid bilayer membranes are NOT symmetrical! 3 Lipid Bilayers are Composed of Different Types of Lipids Cholesterol in a Lipid Bilayer Cholesterol molecules orient themselves with their hydroxyl groups close to the polar heads of the phospholipid molecules. The steroid ring region partly immobilizes the Frst CH 2 groups of the hydrocarbon chains. •Decreases membrane permeability •Decreases membrane ¡uidity •Inhibits possible phase transitions 4 Asymmetry of the Lipid Bilayer is Functionally Important Phosphatidylserine is important for binding of protein kinase C to cytosolic surface of plasma membrane. Glycolipids are located exclusively in the noncytosolic lea¡et - may play important roles in cell protection and cell recognition. Glycolipid Molecules 5 Structure of the Plasma Membrane • Phospholipid Bilayer – Additional components (cholesterol, glycolipids) • Properties of lipid bilayer due to the shape and amphipathic nature of phospholipids – Fluidity – “Prohibition against free edges” • Spontaneous closure to form sealed compartment • Self-healing – Effective diffusion barrier against hydrophilic substances • Inside and outside lea¡ets of lipid bilayers are different (asymmetry) • However, the bilayer structure alone does not explain how charged substances cross the plasma membrane?...
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This note was uploaded on 03/28/2011 for the course BIO 317 taught by Professor Simonhalegoua during the Fall '08 term at SUNY Stony Brook.

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2010 Bio 317 Lecture 2 - 1 Prof. William Collins OfFce: 534...

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