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/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 semi- permeable membrane from an area of greater concentration to an area of lesser concentration to form dynamic equilibrium.

Diffusion hill.com/sites/ /student_view0/ chapter2/animation__how_diffusion_works.htmlhttp://highered.mcgraw- hill.com/sites/ /student_view0/ chapter2/animation__how_diffusion_works.html

Osmosis hill.com/sites/ /student_view0/ chapter2/animation__how_osmosis_works.htmlhttp://highered.mcgraw- hill.com/sites/ /student_view0/ chapter2/animation__how_osmosis_works.html

Passive Transport Osmosis and diffusion of lipids, water and lipid-soluble particles across a semi- permeable membrane is called passive transport because the cell does not use energy.