Lecture 10.3

• The plasma membrane separates life from non life.
• The plasma membrane is a selective barrier.
• The plasma membrane is composed of phospholipids.
• Phospholipids are amphipathic (have a head that interacts with water, has a tait that does not)
• Small or nonpolar molecules move across phospholipid bilayers easily. (oxygen)
• Large or polar molecules move across the phospholipid bilayer slowly. (Glucose)
• Solvents dissolve solutes to create a solution
• lipid bilayers with short, unsaturated tails have high permiability.
• Lipid bilayers with long saturated tails have low permiability.
• Cholesterol molecules decrease membrane permeability because it increases the density.
• There is always a net movement from high-consentration regions to low-consentration regions.
• Equilibrium is when molecules are equally distributed throuout a solution.
• Passive transport occurs when substances diffuse across membranes in absence of an outside energy source.
• Osmosis is the passive transport of water.
• Water moves from regions of low solute concentration to regions of high solute concentration.
• Hypertonic: outside solution has higher concentration (Cell will shrink)
• Hypotonic: outside solution has a lower concentration (cell will swell)
• Isotonic: when the concentration of a solution is the same as the concentration of the cell