BI110 Midterm: Midterm 2 Review
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Document Summary
The barrier separating internal and external contents must: be impermeable to most molecules and ions, be able to exchange molecules and ions between compartments, be insoluble in water, be permeable to water. Functions of a cell membrane include: acting as a boundary, being permeable, acting as a barrier, organizing and localizing function of organelles, aid in transport, aid in signal detection, cell to cell interactions. Amphipathic (hydrophilic head, hydrophobic tale): glycolipids, sterols (cholesterol, membrane proteins (integral or peripheral) Membrane fluidity depends on how densely packed phospholipid molecules can pack together. Influenced by 2 factors: composition of lipid molecule: degree of unsaturation of fatty acid tails, and sterols. Saturated fatty acids are straight in shape and packed tighter. Unsaturated fatty acids contain double bonds between carbons, which introduce kinks. At low temperatures molecules become closely packed, fluidity not maintained, enzymes and proteins cannot function. At high temperatures it becomes too fluid and leakage occurs.