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Unformatted text preview: Membranes 2 Bio 106 Fall 2009 Professor Owen Lecture 6 1 Cholesterol ¡ Multi-ring structure – rigid, plate-like ¡ Present in high concentrations in the plasma membrane (up to 20% of lipids by weight) ¡ Present in animal cells only MBOC 3 10-8 Cholesterol in a Membrane ¡ Cholesterol modulates membrane fluidity ¡ Fills the spaces between neighboring unsaturated lipid tails ¡ 20% of total lipid in membrane by wt. ¡ Stiffens the bilayer and makes it less fluid but helps prevent a gel state at low temperatures ECB 3 11-16 A bacterium adapted to cold temperatures would be expected to have what adaptation in its plasma membrane? A. Increase of unsaturated lipids B. Increase in saturated lipids C. It depends D. Increase in amount of cholesterol Asymmetrical Distribution Proteins and phospholipids are distributed asymmetrically in the membrane. ECB 3 11-17 Orientation Membrane ECB 3 11-19 Faces of cellular membranes Each closed compartment has two faces Lodish 5-31 The two faces of a membrane are asymmetric in terms of lipid and protein composition Membranes 2...
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