2 - Membrane Structure

2 - Membrane Structure - Lecture 2 Membrane Structure and...

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Lecture 2: Membrane Structure and Transport
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How do we learn about cells-5? The logic of experiments What is the question/hypothesis? What is the best method to address the question? Are orthogonal approaches available? The importance of making quantitative measurements How is quantitative data gathered – the importance of assays How is data interpreted – the importance of controls
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1. Cells are bounded by membranes 2. Membranes are 50 Å-thick molecular assemblies composed of both proteins and amphiphilic molecules that spontaneously assemble to form bilayers. There are ~1 billion lipid molecules and ~20 million protein molecules in the plasma membrane of a eukaryotic cell. – what is amphiphilic?
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Figure 10-3 Molecular Biology of the Cell (© Garland Science 2008) The major lipids in cell membranes
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Figure 10-4 Molecular Biology of the Cell (© Garland Science 2008)
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Although the lipids mentioned above comprise two-thirds to three-quarters of membrand lipids, we now know that the remaining ¼ to 1/3rd can comprise upwards of 500-1000 different molecular species. It seems very likely that lipids play critical roles in cell biology that have yet to be discovered. Discovery of lipid structures, their biosynthetic and metabolic pathways, and their functions has greatly lagged discoveries on proteins.
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“Hydrophobic interactions” are really driven by water’s maximizing its disorder and interactions with itself Polar molecules interact with the water Inability of nonpolar molecules to interact with the water causes the water to assume more orderly “cage” with relatively few interactions. This results in a decrease in entropy, which is energetically unfavorable herefore water crowds non-interacting molecules together
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Figure 10-7 Molecular Biology of the Cell (© Garland Science 2008) The shape of lipids has a simple, predictable ‘macroscopic’ effect on the structures they form
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2 - Membrane Structure - Lecture 2 Membrane Structure and...

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