BI110 Lecture Notes - Lecture 24: Lipid Bilayer, Chemical Polarity, Hydrophile
Document Summary
Cells must have a barrier that separates its internal and external contents; this barrier must have the following: Insolubility in water, since the cytosol is dissolved in water. A cell membrane is a phospholipid bilayer, which has membrane proteins (responsible for transportation), sterols (gives more fluidity to the membrane) and glycolipids (carbohydrates attached to the phospholipids) embedded in it. Due to its polarity, water is an excellent solvent. A solvent is a fluid in which a solute can be dissolved. Polar molecules are hydrophilic ( water-loving ), examples are: sugars, dna and some amino acids. Non-polar molecules are hydrophobic ( water-fearing ), they do not dissolve in water (i. e. lipids and carbohydrates). The phosphate heads are polar and hydrophilic, they are made of: glycerol backbone, phosphate group (-) and a variable head group (+). Usually the oxygen or nitrogen molecules allow interactions with water. The 2 hydrocarbon tails have no charger whatsoever, hence they are hydrophobic.
