Lecture 4, membrane structure

Lecture 4, membrane structure - BIO 320 Properties and...

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BIO 320 Properties and Makeup of Membranes
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eukaryotes 1.5 billion years ago 3.5 billion years ago prokaryotes Plants Fungi Animals The original cell Pro = before Eu = true karyon = nucleus
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Typical Prokaryote *
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Typical Eukaryotic Cell Highly compartmentalized, with many membrane-bound compartments
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Basic Functions of Biological Membranes • Protective physical barrier • Selective chemical barrier • Encapsulates specialized compartments • Unique reaction substrate • Supports 2D diffusion
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What are cellular membranes made of? Lipid…………and proteins……… Figure 10-1 Molecular Biology of the Cell (© Garland Science 2008)
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Lipid, 3 major classes: 1. Phospholipid (most abundant) A. Phosphoglyceride B. Sphingolipid 2. Glycolipid 3. Cholesterol (a steroid) All lipid molecules in cell membranes are amphiphilic (i.e., one part hydrophobic [nonpolar] and one part hydrophilic [polar]) What are cellular membranes made of?
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Figure 10-3 Molecular Biology of the Cell (© Garland Science 2008) 4 Major phospholipids within the membranes of mammalian cells Phosphoglycerides Sphingolipid Polar head Glycerol Typically C14 -C24, with one tail being unsaturated PS has net negative charge Nonpolar tails Fatty acid tail in sphingosine tends to be longer and straighter
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Saturated Mono-unsaturated Poly-unsaturated Omega-3 Omega-6 * * * Essential (in diet) Some common fatty acids found in lipid
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Phospholipids: Bilayer arrangement in membranes Figure 2-22 Molecular Biology of the Cell (© Garland Science 2008) Conformation of unsaturated fatty acid tail (more bent) differs from that of saturated ones (more straight). Phosphoglyceride shown here
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Lipid bilayers naturally form spheres Figure 10-8 Molecular Biology of the Cell (© Garland Science 2008) No hydrophobic edge exposed to water, thus energetically more favorable
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In the “fluid mosaic” model of cell membrane, components within the membrane are free to diffuse laterally (unless restricted by various mechanisms)
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Lecture 4, membrane structure - BIO 320 Properties and...

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