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Lecture 3

Lecture 3 readings.docx

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University of Toronto St. George
James Thomson

Lecture 3 readingsChapter 2 pg5164Water is the most abundant substance in cells70 of cell weightmost reactions occur in aqueous environmentunequal distribution of electron in water molecule Positive Hs and negative Ohydrogen bonding occurs Weak bond Combined effect of many bonds is bighydrophilic molecules react with water DNA RNA proteins includedhydrophobic is the opposite Hydrocarbons because they have nonpolar bond with carbon bond is fulfilled and thus like will not dissolve unlike Some polar molecules are Acids and Baseswater can act as acid and baselooking at equilibrium in the forwards and backwards reactions backwards being the conjugate base and acid reactingSubstances that release protons are acidsph stays around 7 in cell as buffers help keep it thereBases accept protons donate electrons Four types of noncovalent attractions help bond molecules in cells1 Electrostatic attractionsResult from attractive forces between oppositely charged atoms Strong in absence of waterReadily form in case of two atoms with permanent dipoles but are strongest with fully charged molecules ionic bonding Water mucks everything up by reducing charge by them placing there own charge to make the molecules happy 2 Hydrogen bonding Hydrogen bonds to a highly electronegative molecule making the hydrogen have a positive charge and the other molecule very negativethe hydrogen portion of the molecule can now bond itself the negative portion of anadjacent molecule juts like itself Very strong if a chain occursWater again mucks things up 3 Van der waals attractionsAttraction between positive nucleus and electron cloud of another moleculeNot effected by water 4 Hydrophobic forcesNot a bondOccurs in waterCaused by pushing of nonpolar surfaces out of hydrogen bonded water network A cell is formed from carbon compounds Carbon can form large molecules
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