BIOL 201 Midterm: Membranes and transport
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16 Aug 2015
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Lecture 9 -10: membranes and solute diffusion, phospholipids: Consist of hydroxyl groups of glycerol esterified with fatty acids. Have a hydrophobic portion and a hydrophilic portion (called the head group). They are the major components of the cell membranes (inner, outer of mitochondria/chloroplast etc) If mix phospholipids in an aquaeous solution it will form a bilayer. Head groups facing the water solvent and hydrophobic parts in the middle (away from water). This is what constitute the basis of a membrane. It is permeable to small molecules (non polar ones like co2 and o2 can cross freely) but impermeable to large polar molecules (need transport mechanism). If there are different concentrations of a type of molecules on both side of the membrane the molecules will cross the membrane from the higher concentration to the lower concentration. This is with the purpose of reaching an equilibrium concentration the movement is then energetically favourable because it is entropy driven. (will take place spontaneously. )
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