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Transcript
Membranes Biology 11 • Plasma Membrane: the outer boundary of a cell that encloses the cells contents. • Selective Permeability: some molecules are able to pass while others are not. – Tea bags, colanders, plasma membranes(!!) • Hydrophilic: water loving • Hydrophobic: fear of water What kind of reaction occurs when you put a hydrophobic substance in water? – Think oil and vinegar Fluid Mosaic Model Three Parts to a Cell Membrane • Phospholipid molecules – (formed into a phospholipid bilayer) • Cholesterol molecule • Membrane protein Phospholipid Molecule Structure • Two fatty acids and one phosphate head. • The fatty acids are hydrophobic and the phosphate head is hydrophilic. Function • The phospholipids pair up, and form a bilayer with the fatty acids touching, and the phosphate heads facing outwards. This creates the cell membrane Phospholipid Molecule Cholesterol Molecule Structure • Rigid molecules embedded in the lipid bi-layer Function • Helps keep the structure of the membrane and keeps the fatty acid tails apart. Carbohydrate in Plasma Membrane Membrane Proteins Structure • Proteins are located throughout the membrane (like raisins in raisin bread) Function • Regulation of what passes the membrane • Serve as enzymes and take part in chemical reactions • Act as markers that are recognized by chemicals in and out of the cell Membrane Proteins Fluid Mosaic Model • telstar.ote.cmu.edu/.../tutorial/cellmemb ranes/ Diffusion and Osmosis • Diffusion: the movement of particles from the area of greater concentration to an area of lesser concentration to form dynamic equilibrium. • Dynamic Equilibrium: condition of continuous movement with no net change. • Osmosis: the movement of water across a semipermeable membrane from an area of greater concentration to an area of lesser concentration to form dynamic equilibrium. Diffusion • http://highered.mcgrawhill.com/sites/0072495855/student_view0/ chapter2/animation__how_diffusion_works .html Osmosis • http://highered.mcgrawhill.com/sites/0072495855/student_view0/ chapter2/animation__how_osmosis_works .html Passive Transport • Osmosis and diffusion of lipids, water and lipid-soluble particles across a semipermeable membrane is called passive transport because the cell does not use energy.
