BSC 2010C Lecture Notes - Lecture 7: Lipid Bilayer, Tonicity, Extracellular Fluid
Document Summary
Membranes organize the chemical activities of the cell, separates cell from outside environment, controls passage of molecules, partitions organelle function in eukaryotes, provides reaction surfaces and increases usable surface area for enzymes and their substances. The membranes are composed of phospholipid bilayers due to the polar head and non polar tail. Membranes are fluid mosaics of phospholipids, lipids, and proteins. Some proteins extend through both sides of the bilayer. Cholesterol helps stabilize animal cell membranes at different temperatures. Original davson daniel model claimed the proteins sandwich the bilayer. Current fluid mosaic model are movable protein within bilayer. Flip flopping from top layer to bottom layer is rare and instigated by the flipase enzyme. Kinked tails n unsaturated fats of the membrane creates fluidity since they can"t be packed tightly. Straight tails in saturated fats are viscous and cause stiff membranes. Cholesterol molecules promote fluidity but maintains the membrane since it is hydrophobic. Two major classes of protein in the membrane.
