BI110 Lecture Notes - Lecture 19: Hydrogen Bond, Electronegativity
Bi110 lecture 19
Fluid Mosaic Supported By: experimental evidence: Membranes are Fluid
• Isolate human cells and isolated mouse cells
• Treated both differently
• Humans labeled with red fluorescent and mouse labeled with green
• Mixed both together under conditions that favor cell fusion
• Visualized under microscope, half were red half were green
• Watched cells over time and saw that they had mixed
• Showed that membrane proteins aren’t fixed in one place and can move
Cell Chemistry Review
Water molecules are polar
• Polarity: uneven distribution of charge
• Hydrogen bonds are short live bonds that only last a few milliseconds
• Not a strong bond but they are when they are all together
• Electronegavitity: oxygen atom associates with electropositive hydrogen
atoms of adjacent water molecules to form hydrogen
• Hydrogen bonds are also important in DNA and protein
Water is an excellent solvent
• Solvent: Fluid in which another substance called a solute can dissolve
• Polar/charged: Hydrogen forms bonds with hydrogen and ionic bonds with
water molecules
• Hydrophilic (water loving): Sugars, DNA, RNA, organic acids, and some amino
acids
• Hydrophobic (water fearing): Don’t dissolve in water. Ex. Lipids,
(hydrocarbons), some amino acids
Hydrophobic Molecules
• No polar regions – water can’t form anything with them
• Don’t interact electrostatically with water
• Disrupt hydrogen bond in water
• Coalesce with each other in water
